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by 

U.S. Department of Energy 

Energy Eff ency and Renewab e Energy 

Federa Energy Management Program 

Un ted States 

Env ronmenta

Protect on Agency 

L a b o r a t o r e s f o r t h e 2 1 s t C e n t u r y : 

B e s t P r a c t c e s 

Steve Hall, Hedrick-Blessing/PIX12657 

ATER FFICIENCY 

UIDE FOR 

ABORATORIES 

Introduct on 

Most laboratory buildings in our country use 

significantly more water per square foot than standard commercial buildings do, primarily to meet 

their larger cooling and process loads. This greater 

need also provides laboratories with more opportunities to make cost-effective improvements in water 

efficiency, especially with respect to the amount of 

water they use in cooling towers and for special process equipment. A laboratory’s water efficiency can 

also be improved by making a few changes in other 

types of equipment, such as water treatment and 

sterilizing systems, as described in this guide. And 

alternative sources of water can often be effectively 

integrated into a laboratory’s operations. 

This guide to water efficiency is one in a series 

of best practices for laboratories. It was produced 

Laboratories for the 21st Century (“Labs 21”), a 

joint program of the U.S. Environmental Protection 

Agency (EPA) and the U.S. Department of Energy 

(DOE). Geared toward architects, engineers, and 

facility managers, these guides provide information 

about technologies and practices to use in designing, constructing, and operating safe, sustainable, 

high-performance laboratories. 

This exterior view of the Nidus Center for Scientific Enterprise in St. Louis, 

Missouri, shows the cisterns that store rainwater used to irrigate the 

grounds of this research facility. 
2 L A B S F O R T H E 2 1 S T C E N T U R Y 

Laboratory Cooling Towers Typical Cooling Tower Operation Drift ("D") 

Water with concentrated 

mineral salts 

Treatment 

chemicals 

Water 

sprayed 

downward 

Evaporation ("E") 

Warm water 

Process 

heat 

source 

Cool water 

Blowdown ("B") 

Water flowing out of a cooling tower 

circulates to equipment that needs cooling. 

The equipment is cooled; the water is 

warmed. The warm water is returned to 

the cooling tower where it is re-cooled 

and the process begins again. 

Cooling towers, which are part of many laboratory 

buildings, might represent the largest single opportunity 

for greater water efficiency. This is because laboratories 

usually have very large comfort-cooling and process 

loads. Laboratories often use 100% outside air for ventilation; this makes their comfort cooling loads higher than 

those of most office buildings. Additional cooling is often 

needed for special equipment such as lasers and electron 

microscopes (see the section on laboratory equipment in 

this guide). In fact, from 30% to 60% of all the water used 

in multipurpose laboratories is for cooling. 

Makeup back to 

water process 

("M") 

Recirculating pump (also called bleed-off) 

Cooling towers use water in three ways: evaporation, 

drift, and bleed-off. Figure 1 illustrates water use in a typical cooling tower. Evaporation (E) is fixed and controlled 

by thermodynamics; about 2.4 gallons per minute (gpm) 

of cooling water is used for every 100 tons of cooling. 

Bleed-off (B) contains the concentrated, dissolved solids 

and other material left behind from evaporation. Drift (D) 

losses are typically a function of tower design. Most of 

today’s tower designs reduce drift to about 0.05% to 0.2%. 

Since the amounts are small and they contain dissolved 

solids, they are usually included in bleed-off. Make-up 

(M) water replaces water lost because of E, B, or D. 

Cooling Tower Water Management 

The primary methods for managing water use in 

cooling towers are operational ones. For example, cooling towers can be investigated to see if there should be an 

Figure 1. Water use in a typical cooling tower 

(Source: New Mexico Office of the State Engineer 1999; reprinted with 

permission) 

results in greater water efficiency (New Mexico Office of 

the State Engineer 1999). 

Figure 2 shows the effect of the CR on make-up water 

use. Note that increasing the CR from 2 to 5 yields almost 

85% of the savings that can be obtained by increasing the 

cycles from 2 to 10. Increasing the cycling above 6 does 

not significantly reduce make-up water use, but it does 

increase the likelihood that deposits will form and cause 

fouling of the system (Puckorius 2002). Any of several 

different parameters can be used to estimate the water 

savings for a specific tower, as shown in the sample 

calculation. 

increase in the concentration ratio (CR) or cycles of concentration of water in the tower. The CR is an indication 

of how many times water circulates in the tower before it 

is bled off and discharged. Increasing the recycle rate of 

the tower reduces the consumption of make-up water and 

To calculate the concentration ratio (CR)

and associated water savings: 

Since the CR represents the relationship between the concentration 

Gallons/day/100 tons of cooling 7000.0 

6000.0 

5000.0 

4000.0 

3000.0 

2000.0 

1000.0 

0.0 

Incremental 

water savings 

2 4 6 8 10 12 14 16 18 20 

of dissolved solids in bleed-off (CB) to the concentration in make-up 

water (CM), it can be expressed as 

CR = CB/CM. 

If a cooling tower is metered for bleed-off and make-up water, CR 

can be calculated as follows where M is the volume of make-up 

water and B is the volume of bleed (in gallons). 

CR = M/B.

The amount of water saved by increasing the CR can be calculated as

Vsaved = M1 * (CR2 - CR1)/CR1(CR2 - 1). 

Here, V is the total volume saved, M1 is the initial make-up water 

volume, CR1 is the initial concentration ratio, and CR2 is the desired 

or final concentration ratio. 

Concentration ratio (CR) 

Figure 2. Incremental water savings 

In addition to savings on water and sewer costs, savings also result from having to purchase fewer chemicals 

to treat the water. As the volume of incoming fresh water 

is reduced, so is the amount of chemicals needed. Table 1 

shows approximate savings on chemical usage resulting 

from increasing the CR in a 10,000-gpm system. 

Perhaps the best way to increase the cycles of concentration is through better monitoring and management of 

the water chemistry. The first step is to understand the 
L A B S F O R T H E 2 1 S T C E N T U R Y 3 

Table 1. Chemical savings resulting

from increasing the concentration

ratio of a cooling tower

Cycles 

Makeup 

(gpm) 

Change 

(gpm) 

Chemical needed 

at 100 ppm (lb) 

Change 

(lb) 

1.5 300 240 

2 200 100 120 120 

4 133 67 40 80 

5 125 8 30 10 

10 111 14 13.3 16.7 

Source: GC3 Specialty Chemicals 2000. Service Document; 

www.gc3.com/srvccntr/cycles.htm. 

quality of the incoming water and what the controlling 

parameter should be, such as hardness, silica, or total dissolved solids. There will be a relationship between these 

parameters and conductivity, based on the water chemistry specific to a site. This relationship can help to establish 

a conductivity set point. The conductivity controller opens 

a blow-down valve as needed to maintain your control 

parameter within acceptable limits. 

Conductivity and flow meters should be installed 

on make-up and bleed-off lines. Meters that display total 

water use and current flow rate provide useful information about the status of the tower and cooling system, so 

they should be checked regularly to quickly identify problems. For example, the conductivity of make-up water and 

bleed-off can be compared with the ratio of bleed-off flow 

to make-up flow. If both ratios are not about the same, 

the tower should be checked for leaks or other unwanted 

draw-offs. 

It is important to select a chemical treatment vendor 

carefully—one who understands that water efficiency 

is a high priority. Vendors should provide estimates of 

the quantities and costs of treatment chemicals, bleed-off 

water volumes, and expected CR. Criteria for selecting a 

vendor should include the estimated cost of treating 1000 

gallons of make-up water and the highest recommended 

cycle of concentration for the water system. 

New construction and renovation projects are excellent opportunities to design for greater water efficiency. A 

plume abatement or hybrid tower is one design that can 

have an impact on water use, even if the primary reason 

for it is to reduce the visible plume* emanating from large 

industrial towers. A smaller plume is desirable in many 

residential areas and in areas where visibility is important, 

such as near airport runways. 

* A plume is the visible column of saturated air exiting a 

conventional cooling tower. 

Hybrid towers have both a wet and a dry cooling section (Figure 3). The tower can be run in wet mode in the 

summer, when the plume is less problematic, at the highest efficiency. In winter, the tower can be run in either dry 

or wet/dry mode. When operating in this mode, the dry 

section warms the exit air stream to raise the temperature 

above the dew point of the surrounding air, reducing 

humidity and thus the size of the plume. 

Hybrid cooling tower performance depends on the 

location and environmental characteristics of the site. 

Energy and water costs also play a crucial role in the decision to use hybrid cooling towers, because making some 

of these towers more water-efficient could have a negative 

impact on energy efficiency. 

Another option for new and retrofitted cooling tower 

designs is to pipe blow-down water to a storage tank. 

This water can then be reused for nonpotable needs, such 

as bathroom commodes or fire suppression systems. 

Facilities should exercise caution when using blow-down 

water, however, as it can be extremely high in dissolved 

solids as well as chemical by-products from the water 

treatment process. The quality of blow-down water 

should be checked to make sure that it will not clog, foul, 

or otherwise damage other systems. 

Special Water-Efficient Features 

Special features of towers and water systems that 

promote water efficiency include side-stream filtration, 

sunlight covers, alternative water treatment systems, and 

automated chemical feed systems. 

Air 

out 

Hot 

Dry 

section 

Air 

in 

Air 

in 

Wet 

section 

Airflow 

control louvers 

Mixing chamber 

Dampers Hot 

water water 

in in 

Air Air 

in in 

Cold 

Figure 3. A hybrid cooling tower 

Source: EPRI and CEC 2002. 
4 L A B S F O R T H E 2 1 S T C E N T U R Y 

Side-stream filtration systems cleanse the water with 

a rapid sand filter or high-efficiency cartridge filter. These 

systems increase water efficiency and use fewer chemicals 

because they draw water from the sump, filter out sediment, and return filtered water to the tower. Side-stream 

filtration is particularly helpful for systems that are subject 

to dusty atmospheric conditions. 

Sunlight covers can reduce the amount of sunlight 

(and thus heat) on a tower’s surface. They can also significantly reduce biological growth, such as algae. 

Alternative water treatment options, such as ozonation or ionization, can reduce water and chemical usage. 

Such systems can have an impact on energy costs, however, so managers should carefully consider their life-cycle 

cost. 

Automated chemical feeds should be installed on 

cooling tower systems larger than 100 tons. An automated 

feed system controls bleed-off by conductivity and adds 

chemicals according to the make-up water flow. Such 

systems minimize water and chemical use while optimizing the control of scale, corrosion, and biological growth 

(Vickers 2002). 

Laboratory Process Equipment 

Three broad areas in which the water efficiency of 

a wide range of laboratory process equipment can be 

improved are cooling of equipment, rinsing, and flow control. These areas can be addressed individually or together 

to increase the water efficiency of most laboratories. 

Equipment Cooling 

Single-pass cooling typically consumes more water 

than any other cooling method in laboratories. In singlepass or once-through cooling systems, water is circulated 

once through a piece of equipment and then discharged to 

a sewer. Single-pass systems use approximately 40 times 

more water than a cooling tower operating at 5 cycles of 

concentration to remove the same heat load. 

The equipment typically associated with single-pass 

cooling are CAT scanners, degreasers, hydraulic equipment, condensers, air compressors, welding machines, 

vacuum pumps, ice machines, X-ray equipment, air conditioners, process chillers, electron microscopes, gas chromatographs, and mass spectrometers. Sometimes, research 

staff members order and install these and other types of 

equipment that require cooling without consulting facility 

management. The equipment is usually connected directly 

to a public water supply, and it drains to a sewer. 

The best way to combat the water waste associated 

with single-pass cooling is to use a process or cooling 

loop. This loop provides water at a preset temperature to 

cool researchers’ equipment. A small packaged chiller or 

central plant towers can reject the heat from these systems. 

Other efficient options include reusing single-pass 

discharge water for irrigation or initial rinses, or for recovering the heat from one process for use in another. 

Often, the equipment in this category is used only 

intermittently. So, it can be quite difficult to determine 

how much of a laboratory’s total water use goes to process 

equipment. A water meter on the process loop can provide 

this kind of information. By separating laboratory water 

from domestic, irrigation, or other cooling water, facility managers can better monitor water quality and usage 

across the whole facility. 

The more complicated equipment used in today’s laboratories often requires tighter or more stable temperature 

control (or both) than a centralized system can provide. 

Small packaged chillers allow this control and reduce 

water usage. Such chiller systems consist of a compressor, 

condenser, evaporator, pump, and temperature controller in one small package. The packaged unit recirculates 

temperature-controlled fluid to a laboratory application 

to remove heat and maintain a constant temperature. The 

recirculating fluid picks up heat from the application and 

returns to the chiller to be cooled to a specified set point 

before circulating back to the application. 

Packaged chillers work in somewhat the same way 

that large comfort-load chillers do. Laboratory managers 

may want to compare the amount of energy used by different packaged chillers at both part and full loads, and 

select the most efficient one that meets their needs. 

Removing the chiller’s heat can be done by rejecting 

the heat to either air or water. If an air-cooled condenser is 

used, it is better to use a design that rejects heat to the outside air rather than to conditioned laboratory space. The 

second option would increase inside temperatures and the 

amount of energy needed for space conditioning. An alternative is to reject the heat to water (Krupnick 2000). 

In this case, the cooling water should be recirculated 

chilled water, or recirculated through a cooling tower. 

Using once-through cooling water for this purpose is not 

recommended. 

Equipment Used in Rinsing 

Rinsing equipment can often be made more efficient. 

A counter-current rinsing operation is typically the most 

efficient method (Figure 4). In counter-current rinsing, the 

flow of rinse water is opposite to that of the workflow. The 

basic premise is to use the cleanest water only for the final 

or last stages of a rinse operation; water for early rinsing 

tasks, when the quality of the rinse water is not as important, is obtained later in the process. Other efficient rinsing 
L A B S F O R T H E 2 1 S T C E N T U R Y 5 

Work flow 

Water flow 

Third rinse 

tank 

Second rinse 

tank 

First rinse 

tank 

Rinsewater 

in 

Rinsewater 

out 

Figure 4. Schematic diagram of counter-current rinsing process 

(Source: New Mexico Office of the State Engineer 1999; reprinted with 

permission) 

options include batch processing, in which several pieces 

are cleaned at the same time, and using rinses from one 

process in another one. 

Flow Control 

Many pieces of lab equipment are “on” continuously, 

even when the process runs only a few hours per day or 

a few days per year. Often, the water flow to some of this 

equipment is only a few gallons per minute. However, a 

continuous 1.5-gpm trickle flow through a small cooling 

unit adds up to 788,400 gallons per year. 

Using a control or solenoid valve in these applications 

allows water to flow only when the unit is being used. 

Another option is to use shut-off valves or timers to turn 

equipment off after normal working hours and when a 

process is shut down for maintenance or other reasons. 

Laboratory Specific Best Practices 

Water efficiency is an important consideration not 

only for special process equipment but in other lab equipment, as well. This includes equipment used in laboratory 

water treatment, sterilization, photographic, X-ray, and 

vacuum systems. 

Water-Treatment Equipment 

In their day-to-day operations, many laboratories 

require high-quality water or water free from mineral and 

organic contaminants. There are five basic levels of separation processes: particle filtration, microfiltration, ultrafiltration, nanofiltration, and hyperfiltration. A filtration 

spectrum (see www.gewater.com/library/ ) illustrates 

the separation process and size range for common types 

of materials. Typically, as finer and finer particles are 

removed, energy use and water waste increase. Therefore, 

facility managers will want to choose a filtration process 

that matches their requirements. For example, reverse 

osmosis (RO) water should be used only in processes that 

require very pure water. Because RO produces the purest 

water, it usually requires the most energy and materials 

and results in the most waste. 

Two streams exit the RO system: the concentrate 

stream and filtered, purified water. The concentrate is 

rejected water containing a high level of dissolved minerals. The concentrate is then typically sent to a drain, or a 

portion of it is recycled back to the feed stream to increase 

the system’s overall water recovery. Although the concentrate is high in dissolved minerals, it can be reused in nonpotable applications (e.g., in bathroom commodes) (See 

Figure 5). However, as with cooling tower blow-down, 

water quality should be monitored to avoid fouling other 

systems. The recovery rate (i.e., the ratio of the filtered 

purified water to the volume of feed water) is typically 

50% to 75% for a conventional RO system operating on 

city feed water. 

Disinfection/Sterilization Systems 

Two types of systems are used for disinfection in laboratories: sterilizers and autoclaves. Sterilizers use water 

to produce and cool steam and to cool wastewater before 

discharge. Some units also use water to draw a vacuum 

to expedite the drying process. Water use in sterilizers 

ranges from 1 to 3 gpm. Autoclaves use ethylene oxide as 

the sterilizing medium rather than steam. Water is used to 

To make a water purification system more

efficient:

• Evaluate the laboratory’s requirements for high-quality water, 

including the total volume and the rate at which it will be needed, 

so that the system can be properly designed and sized. 

• Determine the quality of water required in each application; use 

the lowest appropriate level of quality to guide the system design 

(FEMP 2004). 

• Evaluate the quality of the water supply for a period of time 

before the system is designed. This evaluation allows designers 

to accurately characterize the quality of the water supply and 

helps them determine the best method for attaining the quality 

level required. For example, city water contains a wide range of 

impurities. EPA suggests a limit of 500 mg/L for total dissolved 

solids (TDS) (see also www.epa.gov/safewater/). Note that 

the TDS of one public water supply has ranged from 33-477 

mg/L over the course of a year (New York City Department of 

Environment 2003). 

• Consider using one of the proprietary systems for improving 

system efficiency; some claim recovery rates up to 95%. 
6 L A B S F O R T H E 2 1 S T C E N T U R Y 

To make autoclaves and sterilizers more

efficient:

• Purchase new equipment only if it is designed to recirculate 

water or allows the flow to be turned off when the unit is not in 

use, or both. 

• Adjust flow rates to the minimum ones recommended by the 

manufacturer, and review and readjust them periodically.

• Install a small expansion tank instead of using water to cool steam 

for discharge to the sewer. Check with the manufacturer to make 

sure this will not interfere with the unit’s normal operation. 

• Shut off units that are not in use, or install an automatic shut-off 

feature if it does not interfere with the unit’s normal operation. 

• Use high-quality steam for improved efficiency (New Mexico 

Office of the State Engineer 1999).

• Use uncontaminated, noncontact steam condensate and cooling 

water as make-up for nonpotable uses, such as in cooling towers 

and boilers (Vickers 2001). 

• Consider purchasing a water conservation retrofit kit; many are now 

available for older units. They reduce water use by either controlling 

the flow of tempering water or by replacing the venturi mechanism 

for drawing a vacuum. Tempering kits sense the discharge water 

temperature and allow tempering water to flow only as needed. 

This can save about 2900 gallons per day when equipment is in idle 

mode. Venturi kits replace the venturi with a vacuum pump, saving 

approximately 90 gallons per cycle (Van Gelder 2004). 

remove the spent ethylene oxide and, like sterilizers, some 

units use water to draw a vacuum to expedite drying. 

Their water usage ranges from 0.5 to 2 gpm. 

Both autoclaves and sterilizers can consume large 

amounts of water, depending on the size, age, and use rate 

of the unit. Often, these units are operating 24 hours per day, 

averaging about 16 hours in idle mode (Van Gelder 2004). 

Because older units typically have no option for flow control, they can waste a lot of water. Laboratories and medical facilities often have a large number of these units. 

Photographic and X-Ray Equipment 

Photographic and X-ray machines typically use a 

series of tanks and dryers to develop and process film. A 

typical X-ray film-processing machine requires a water 

flow of about 2 gpm. However, many processors use flow 

rates that are higher than necessary to ensure acceptable 

quality, sometimes as much as 3-4 gpm. Tap water is often 

used once for developing purposes and then allowed to 

drain into the sewer system. Newer machines use less 

water in the process and allow less of the silver used in 

developing to be discharged as waste. 

To eliminate water use in photographic departments, 

some facilities have moved to digital X-ray and photography, and computerized printing. This change also 

To use less water in photographic and

X-ray processing:

• Adjust the film processor flow to the minimum acceptable rate. 

This may require installing a control valve and a flow meter in 

the supply line. Post minimum acceptable flow rates near the 

processors. 

• Recycle rinse bath effluent as make-up for the developer/fixer 

solution. A silver recovery unit can also be helpful in recovering 

metal for later use. 

• Install a pressure-reducing device on equipment that does not 

require high pressure. 

• If the processor has a solenoid or an automatic shut-off valve for 

times when the unit is not in use, check it regularly to ensure that 

it is working properly (New Mexico Office of the State Engineer 

1999). A malfunctioning valve can let water flow when the 

system is in standby mode. 

• Consider using one of the proprietary water efficiency devices 

for X-ray and photo processing. Some reuse water, and in 

emergencies, they can run equipment on only 15 gallons (see 

also www.caxray.com/products_water_save_plus.html). 

• Replace older equipment with newer, more efficient models. Look 

for models with a squeegee that removes excess chemicals from 

the film. This can reduce chemical carryover by 95% and reduce 

the amount of water needed in the wash cycle (Vickers 2001). 

eliminates the need for chemicals used in photographic 

processing. 

Vacuum Systems 

Wet chemical laboratories often employ faucet-based 

aspirators to create a venturi-type siphon, used as a vacuum source. These systems can apply a vacuum to laboratory filtration systems for extended periods of time. A better 

approach would be to install a laboratory vacuum system 

or to employ small electric vacuum pumps to create the 

pressure differentials necessary for vacuum applications. 

Dishwashers 

Laboratory dishwasher systems use deionized or RO 

water to deliver water of different qualities in the rinse 

cycles. They are designed to remove chemical build-up 

on glassware, pipettes, and other types of equipment. 

Newer dishwashers use less water than older models. With newer models, the operator can also select the 

number of rinse cycles. Fewer cycles should be selected 

whenever possible, if that will not affect the quality of the 

product. 

Vivariums 

Vivariums use equipment and practices specific to 

animal care, such as automatic animal watering systems. 

These can consume large volumes of water because of 
L A B S F O R T H E 2 1 S T C E N T U R Y 7 

To reduce the amount of water used by

dishwashers:

• Run dishwashers only when they are full. 

• Use newer, cleaner rinsing detergents. 

• Reduce the number of rinse cycles whenever possible. 

the need for constant flows and frequent flushing cycles. 

If it is properly sterilized, this water can be recirculated 

in the watering system rather than discharged to drains. 

Where this water cannot be recycled for drinking because 

of purity concerns, if it is sterilized, it is still likely to be 

acceptable for other purposes, such as cooling water 

make-up, or for cleaning cage racks and washing down 

animal rooms. 

It is also possible to reduce the amount of water used 

for some process equipment (e.g., cage washers and sterilizers) in laboratory vivariums. For example, small cages 

are typically cleaned in a tunnel washer; laboratories 

could reuse the final rinse water from one cage-washing 

cycle in earlier rinses in the next washing cycle, by making 

use of a counter-current flow system. 

Alternative Water Sources 

Large facilities, such as laboratory buildings, are 

good candidates for alternative, or unconventional, water 

sources because they usually use a large amount of nonpotable water. This section describes some ways that facilities can greatly increase their total water supply without 

adding capacity from the public system or well. 

The two most useful water sources for laboratory 

buildings are air-conditioning condensate recovery and 

rainwater harvesting. Both can provide fairly steady 

sources of relatively pure water; they are limited primarily by the cost of capturing the water. Another source is 

reclaimed effluent from wastewater treatment plants. 

Utilities often supply this kind of water at reduced prices. 

Condensate Recovery 

In many places in the United States, mechanical space 

conditioning generates significant quantities of condensate, as warm humid air is cooled and dried for temperature and humidity control. The condensate from air 

conditioners, dehumidifiers, and refrigeration units can 

provide facilities with a steady supply of relatively pure 

water for many processes. Laboratories are excellent sites 

for this technology because they typically require dehumidification of a large amount of 100% outside air. 

The potential for condensate recovery depends on 

many factors, such as ambient temperature, humidity, 

load factor, equipment, and size. However, because this 

technique is relatively new, there are no established formulas for calculating the exact amount that can be 

collected from a given system. 

Condensate water is relatively free of minerals and 

other solids. In most cases, it is similar in quality to distilled water. This makes it an excellent source for cooling 

tower or boiler make-up and RO feed water, for example. 

Another advantage of using condensate for cooling tower 

make-up is that there is usually a good seasonal correlation between condensate supply and cooling tower 

demand. Additional savings could result from reduced 

chemical usage and lower membrane maintenance costs. 

Figure 5 (next page) illustrates how water from several 

sources, including AC condensate, can be piped into one 

storage tank for reuse in nonpotable water applications. 

Condensate should not be considered potable because 

it can contain dissolved contaminants and bacteria. 

However, because biocide is added to cooling towers, 

condensate is an excellent option for cooling tower makeup. For laboratories that are not medical or bacteriological 

research facilities, condensate should be safe to use for 

drip-type irrigation. However, medical and other facilities 

could use disinfected condensate in spray-type irrigation. 

Normal chlorine feed equipment, ozone, or ultraviolet disinfection should be effective. It is best to use condensate 

in a process that provides an additional level of biological 

treatment (Hoffman). 

Rainwater Harvesting 

Rainwater is another excellent source of nonpotable 

water. It can be used in many of the applications in which 

condensate recovery water is used. Typically, however, 

rainwater contains fewer impurities than potable water 

Predicting water recovery from condensate 

The cities of San Antonio and Austin, Texas, developed some rules 

of thumb that can be used anywhere for condensate recovery 

systems that are working well in their particular climates. By 

observing installed systems, they found that from 0.1 to 0.3 gallon 

of condensate could be collected for every ton-hour of operation 

of their cooling equipment. A ton-hour is the amount of cooling 

capacity of a one-ton air-conditioning system operating for one 

hour. They also found that the 0.1-0.3 conversion factors (CF) were 

largely associated with levels of ambient humidity. For example, 

they could assume 0.1 gallon would be produced at a humidity of 

less than 70%, 0.2 gallon would be produced at above 80%, and 

0.3 gallon at above 90%. The load factor is the ratio of average load 

during a period to the peak load and is expressed as a percentage: 

Gallons of condensate = (load factor %) (CF) 

(cooling equipment tonnage).

Source: Wilcut and Lillibridge 2004.
��

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8 L A B S F O R T H E 2 1 S T C E N T U R Y

The Austin condensate recovery project:

lessons learned

The Texas Department of Transportation’s Research and Technology 

Center (RTC) is a 53,376-ft2 highway materials and testing 

laboratory in Austin. Austin’s climate features long hot summers 

(2907 cooling degree days) and mild winters (1737 heating degree 

days). The relative humidity averages 74%-79%, depending on the 

season; fall is the most humid. Average annual precipitation is 32 

inches, according to Austin Energy. 

To use water more efficiently, the RTC installed a condensate 

recovery system in September 2002. The system was designed to 

recover condensate from five rooftop air-handling units. The site 

engineer calculated annual water recovery of 321,227 gallons with 

a peak flow of 218 gallons per hour (gph). A measurement taken 

in September 2002 showed a flow rate of 199 gph. The system is 

designed to collect all the condensate and discharge it to the basin 

of the cooling tower. After two years of operation, no major impacts 

on the tower have been noted. 

The RTC system was designed to capture water in three tanks 

holding up to 20 gallons each. The tanks were sized to reduce the 

cycling time of the condensate pumps. The system was installed 

as a retrofit at a cost of $12,774. Annual savings from the project 

were estimated at $2,254, which includes water and sewer fees, for 

a payback of 6 years, according to Carl Nix, RTC engineer. Here are 

some lessons learned from the project: 

• Use a polymer tank to prevent corrosion. RTC used a steel tank 

because it costs less, but then corrosion became a problem. AC 

condensate is fairly pure and thus fairly aggressive. 

• Hard-wire the condensate pumps to prevent nuisance tripping. 

The RTC pumps were connected to weather-protected ground 

fault interrupter receptacles to save money. But exposure to 

water made them trip fairly often, causing the tanks to overflow 

onto the roof. 

• When recovered condensate is used for cooling tower makeup, the system can operate at full flow because the quantity of 

make-up needed usually exceeds the amount of condensate 

recovery. 

• Check to see if adjustments are needed to the water treatment 

chemistry to compensate for higher levels of bioactive 

compounds and pH. 

Source: Austin, Texas, RTC condensate recovery project site 

engineer.

from a public drinking water supply. The only cost is the 

capital cost of equipment to collect and store the water 

(which can be significant). Storm water from other impervious surfaces besides rooftops can also be collected. 

However, because storm water is not as high in quality 

as rooftop rainwater, it is best to use storm water only for 

irrigation. 

Rainwater systems typically consist of six elements: 

the roof or catchment area; gutters, downspouts, or roof 

drains; leaf screens and roof washers that remove debris 

and contaminants; cisterns or storage tanks; a conveyance 

system; and a treatment system. Leaf screens are effective 

in removing large debris from the system. 

The storage tank or cistern is the most costly element. 

It can be either above or below ground, but close to supply 

and demand points to minimize piping needs. It should 

have a tight-fitting lid to prevent evaporation and to keep 

out mosquitoes, animals, and sunlight (which allows algae 

to grow). 

Laboratories considering the use of rainwater should 

check with local or state governments about possible 

restrictions. Many states, particularly those in the West, 

restrict rainwater use. The restrictions have to do with 

water rights laws, which are complex and vary according 

to the jurisdiction. Some allow facilities to detain water for 

irrigation and other uses that return the water back to the 

system, but they do not allow water to be retained permanently on a site. 

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Figure 5. Nonpotable Water Collection and Reuse 
L A B S F O R T H E 2 1 S T C E N T U R Y 9 

To determine the amount of rainwater that 

can be collected at a site: 

First, determine the collection area, average rainfall, and collection 

efficiency. The collection area is the total square footage of the 

roof or catchment area. The average rainfall for a site can be 

obtained from National Weather Service data. Because of seasonal 

variations, rainwater should be considered in terms of variable 

monthly supply and demand for supplemental uses. To develop a 

collection range, use average rainfall as a maximum and half the 

average rainfall as a minimum, to represent drought conditions. The 

conversion factor is as follows: 1 inch of precipitation on 1 square 

foot of collection area yields 0.6233 gallon. 

Rainwater volume (gal) = collection area (ft2) * collection efficiency 

(%) * avg. rainfall (in.) * 0.6233 (gal/in.). 

The collection efficiency depends on such factors as roof material, 

diversion amount, and design retention. The smoother, cleaner, and 

more impervious the roof surface, the more high-quality water can 

be collected. Pitched metal roofs lose negligible amounts of water, 

concrete or asphalt roofs lose an average of about 10%, and built-up 

tar and gravel roofs lose as much as 15%. Flat roofs can retain as 

much as half an inch. Some water is lost to spillover in drains and 

gutters; some cisterns become full during periods of heavy rain, 

and some water can be lost to overflow. So, many installers assume 

efficiencies between 75% and 90% (Texas Water Board 1997). 

Rainwater and condensate recovery systems can be 

expensive to install as retrofits. Storage capacity in particular is expensive. However, properly sizing the system to 

match demand to supply could greatly reduce costs. The 

real value of these systems comes from the high quality of 

water they provide. 

A laboratory complex in Washington, D.C., provides 

a hypothetical example of rainwater harvesting. The site 

receives an average of 43 inches of precipitation each year. 

The complex has a roof area of 54,000 ft2. With a collection 

efficiency of only 75%, the facility could capture about 

1,085,477 gallons of rainwater annually. The site would 

save on both water and sewer fees if water normally 

drains to the sewer. Using a pricing rate similar to those in 

the condensate recovery example, this system would save 

$5,970 per year in water costs. 

Reclaimed Wastewater 

Reclaimed wastewater is an option in limited circumstances, when a laboratory has access to municipal 

wastewater that has been treated to a secondary disinfection level or when treated wastewater can be generated 

cost effectively on site. Reclaimed wastewater might be 

used for some nonpotable applications, such as cooling 

tower make-up. An example is the Nicholas C. Metropolis 

Modeling and Simulation Center at Los Alamos National 

Laboratory (LANL) in New Mexico. The center uses treated wastewater from the LANL complex for cooling tower 

applications. 

The EPA regulates wastewater discharge but does 

not regulate water reuse applications or quality. There are 

uniform national requirements only for biological oxygen 

demand, total suspended solids, and pH. The National 

Pollutant Discharge Elimination System (NPDES) regulates all other contaminants by region and body of water. 

Design Considerations 

One of the most important ways to begin using water 

more efficiently is to create a water balance. A water balance shows the sources and uses of water on a site. It can 

be very detailed or cover only major uses; it can show 

usage at the whole site or in certain buildings or operations. The objective is to show where and how water is 

being used, what the sources are, and how much water 

is being disposed of. In new facilities, a balance can help 

designers plan equipment layouts and identify opportunities for greater efficiency. In existing facilities, it can help 

laboratory managers identify leaks, other losses, and possible misuses. Although it is not possible to account for 

every drop, well-managed facilities can usually account 

for 85%–95% of the water they purchase. 

Creating a Water Balance 

The first step is to document all major water-using 

equipment and processes at the site and usage amounts. 

The water quality required for each use can also be included, as well as information about the local climate, such 

as monthly averages for evapotranspiration rate, relative 

humidity, temperature, and precipitation. 

To find the source of an imbalance in water 

purchases vs. water usage: 

• Check grounds and facilities for obvious water or steam leaks in 

piping, distribution, chilled water or irrigation systems, and other 

equipment. 

• Check the main water meter at night and again in the morning to 

see if there is a large amount of unexplained usage that indicates 

a leak in the system. 

• Review recent utility bills (about 2 years’ worth) to understand 

trends in water use over time. 

• Complete a detailed survey of staff and equipment to identify or 

verify the principal water users and water-using equipment. 

• Ask researchers and facility staff how their equipment is being 

used, if actual usage is higher than original estimates. 
10 L A B S F O R T H E 2 1 S T C E N T U R Y 

X 

X 

X 

Sewer 

Fresh 

water 

Cooling 

towers 

Lawn/grounds 

irrigation 

UPW 

Exhaust 

scrubbers 

Sewer After Construction

Fresh 

water 

Cooling 

towers 

Lawn/grounds 

irrigation 

UPW 

Exhaust 

scrubbers 

Before Construction 

AWN 

FAB 

AWN 

FAB 

Figure 6. The diagrams show how water efficiency measures at an Intel plant in Rio Rancho, New Mexico, have changed the way in which 

water flows through the facility (UPW = ultra-pure water; FAB = fabrication plant; AWN = acid waste neutralization facility). 

(Source: New Mexico Office of the State Engineer 1999; reprinted with permission) 

The second step is to determine whether known purchases equal known usage. If these two are in balance, the 

next step is to look for opportunities for greater efficiency 

in each major usage category and determine whether 

water from one process can be used elsewhere cost 

effectively. If purchases and usage do not balance, however, more investigation is needed. Often, the chief culprit is a lack of information. A thorough review can help 

laboratory managers fill in any missing information and 

discover the source of the imbalance. 

Figure 6 shows a water balance for a microprocessor 

plant near Albuquerque, New Mexico. By rethinking the 

water quality needs of certain applications, plant staff 

were able to use water discharges from one process for a 

number of others. For example, reject water from ultrapure water systems can be used to irrigate the grounds. 

Ultra-pure water discharged from fabrication processes is 

clean enough for use in cooling towers and exhaust scrubbers. The company also implemented a number of efficiency measures within the plant to make better use of water. 

The plant has been able to maintain water use at about 4 

million gallons per day despite an increase in production 

of 70% (New Mexico Office of the State Engineer 1999). 

Design Planning 

Laboratory designers will want to consider water uses 

and sources early in the design process. The following list 

shows where each topic discussed in this guide should be 

addressed in the design process. 

During the Schematic Design Phase 

• Identify appropriate alternative water sources. 

• Locate collection or storage areas. 

• For multibuilding campuses, design the building layout to reduce the size of the distribution system. 

• Include a process or cooling loop for all equipment. 

• Include a vacuum system. 

• Include condensate and chilled water return systems. 

During the Design Development Phase 

• Identify any processes that can use water from other 

processes or that can supply water to processes. 

• Meter all major water-using processes. 

• Select equipment with water-saving features. 

C o n clu sio n 

Because laboratories need more water to meet process 

and cooling loads, among other requirements, they usually use much more water per square foot than conventional 

commercial buildings do. However, this greater usage 

also provides laboratories with significant opportunities 

to reduce their total water use by making cost-effective 

improvements wherever possible. Many government 

agencies and organizations—such as the DOE Federal 

Energy Management Program, the EPA, and the American 

Water Works Association—have published guidelines and 

recommendations on water efficiency for industrial, commercial, and laboratory buildings. These water efficiency 

guidelines can help you use less water today to ensure 

that the nation will have safe, secure supplies tomorrow. 
L A B S F O R T H E 2 1 S T C E N T U R Y 11 

References 

American Water Works Association (AWWA). 1993. 

Helping Businesses Manage Water Use: A Guide for Water 

Utilities. Denver, CO: AWWA. 

Electric Power Research Institute (EPRI) and 

California Energy Commission (CEC). 2002. Comparison 

of Alternate Cooling Technologies for California Power 

Plants: Economic, Environmental, and Other Tradeoffs. 

Palo Alto, CA: EPRI; Sacramento, CA: CEC. Available 

at www.energy.ca.gov/reports/2002-07-09_500-02-

079F.PDF. Accessed August 2004. 

Federal Energy Management Program. June 2004. 

Saving Energy, Water and Money with Efficient Water 

Treatment Technologies, A FEMP Technology Focus. DOE/ 

EE-0294. Washington, DC: U.S. Department of Energy. 

Hoffman, Bill. Coordinator—Commercial Industrial 

Programs, City of Austin, TX, water department. 

Krupnick, Stu. July 2000. “Realizing Chillers’ 

Capabilities in Laboratories.” Process Cooling and 

Equipment, A Supplement to Process Heating Magazine. 

Available online at www.process-cooling.com/CDA/ 

ArticleInformation/features/BNP__Features__Item/ 

0,3674,7515,00.html. Accessed August 2004. 

New Mexico Office of the State Engineer. July 1999. 

A Water Conservation Guide for Commercial, Institutional 

and Industrial Users. Albuquerque, NM: Office of the 

State Engineer. Available online at www.seo.state.nm.us/ 

water-info/conservation/pdf-manuals/cii-users-guide. 

pdf. Accessed August 2004. 

New York City Department of Environmental 

Protection. 2003. New York City Drinking Water Supply 

and Quality Report. Available online at www.nyc.gov/ 

html/dep/pdf/wsstat03.pdf. Accessed August 2004. 

Puckorius, Paul. November 2002. “Water 

Conservation Via Optimizing Water Use.” Process 

Cooling and Equipment, A Supplement to Process Heating 

Magazine. Available online at www.process-cooling. 

com/CDA/ArticleInformation/Water_Works_Item/ 

0,3677,87663,00.html. Accessed August 2004. 

Tanner, Stephanie, Eva Urbatsch, and Anna 

Hoenmanns. 2003. Water Efficiency Plan. Internal 

Publication. Golden, CO: National Renewable Energy 

Laboratory. 

Texas Water Development Board. 1997. Texas Guide 

to Rainwater Harvesting, Second Edition. Austin: Texas 

Water Development Board. 

Van Gelder, Roger E. 2004. “Field Evaluation of Three 

Models of Water Conservation Kits for Sterilizer Trap 

Cooling at University of Washington.” Presented at the 

2004 Water Sources Conference & Exposition, January 

11–14, Austin, Texas. 

Vickers, Amy. 2001. Handbook of Water Use and 

Conservation. Amherst, MA: Water Plow Press. 

Wilcut, Eddie, and Brian Lillibridge. 2004. 

“Condensate 101—Calculations and Applications.” 

Presented at the 2004 Water Sources Conference & 

Exposition, January 11-14, Austin, Texas. 

Additional Resources 

Federal Energy Management Program. Best 

Management Practices for Water Conservation at Federal 

Facilities. Washington, DC: U.S. Department of Energy. 

Available online at www.eere.energy.gov/femp/ 

technologies/water_fedrequire.cfm. Accessed August 

2004. 

North Carolina Department of Environment and 

Natural Resources’ Division of Pollution Prevention 

and Environmental Assistance, Water Efficiency: Water 

Management Options. Available online at http:// 

www.p2pays.org/ref/04/03101.pdf. Accessed September 

2004. 

U.S. Department of Defense. Military Handbook 

1165: Water Conservation. Washington, DC: DoD, 7 April 

1997. Available online at https://energy.navy.mil/ 

publications/water/mil_hdbk_1165.pdf. Accessed 

August 2004. 

Acknowledgments 

Stephanie Tanner was the principal author of this 

publication. The author wishes to thank Bill Hoffman, City 

of Austin Water Department, for information on rainwater harvesting and A/C condensate recovery, and James 

Kohl, URS Corp., for initial research. Roy Sieber of ERG 

and Otto Van Geet, P.E., Nancy Carlisle, A.I.A, and Sheila 

Hayter, P.E., all of NREL, provided helpful comments and 

peer reviews. Paula Pitchford and Susan Sczepanski of 

NREL provided editing and graphic design. 
DOE/GO-102005-2008 

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202-646-5218 

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202-564-7509 

amon.dan@epa.gov 

202-586-3120 

william.lintner@ee.doe.gov 

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12 L A B S F O R T H E 2 1 S T C E N T U R Y 

Laboratories for the 21st Century 

U.S. Environmental Protection Agency 

Office of Administration and Resources Management 

www.labs21century.gov 

In partnership with the 

U.S. Department of Energy 

Energy Efficiency and Renewable Energy 

Bringing you a prosperous future where energy is clean, abundant, 

reliable, and affordable 

www.eere.energy.gov 

Prepared at the 

National Renewable Energy Laboratory 

A DOE national laboratory 

May 2005 

Printed with a renewable-source ink on paper containing at least 

50% wastepaper, including 20% postconsumer waste 

For More Informat on 

On Water-Eff ent Laborator es: 

Stephanie Tanner 

National Renewable Energy Laboratory 

901 D Street, S.W., Suite 930 

Washington, D.C. 20024 

stephanie_tanner@nrel.gov 

On Laborator es for the 21st Century: 

Dan Amon 

U.S. Environmental Protection Agency 

1200 Pennsylvania Ave., N.W. (mail code 3204R) 

Washington, DC 20460 

Will Lintner 

U.S. Department of Energy 

Federal Energy Management Program 

1000 Independence Ave., S.W. 

Washington, DC 20585 

Best Pract ces on the Web: 

www.labs21century.gov