Chapter 8—Rural Water Supplies and Water-quality Issues

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1

Water Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1

Source Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-2

Well Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-3

Sanitary Design and Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Pump Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Dug and Drilled Wells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Cisterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Disinfection of Water Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-7

Chlorine Carrier Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Routine Water Chlorination (Simple) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Well Water Shock Chlorination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Backflow, Back-siphonage, and Other Water Quality Problems . . . . . . . . . . . . . . . .8-9

Backflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Back-siphonage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-10

Other Water Quality Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-10

Protecting the Groundwater Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-10

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-11

Additional Sources of Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-12

Figure 8.1. U.S. Water Supply by Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-1

Figure 8.2. Cross Section of a Driven Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-3

Figure 8.3. Well Seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Figure 8.4. Converted Dug Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-4

Figure 8.5. Recapped and Sealed Dug Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5

Figure 8.6. Drilled Well. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5

Figure 8.7. Typical Dug Well . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-5

Figure 8.8. Sewage in Drainage Ditch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Figure 8.9. Drilled Well. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Figure 8.10. Spring Box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-6

Table 8.1. Recommended Minimum Distance Between Well and Pollution Sources . . . . . . . .8-2

Table 8.2. Types of Wells for Accessing Groundwater, Well Depths, and Diameters . . . . . . . . .8-3

Table 8.3. Disinfection Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-7

Table 8.4. Chlorination Guide for Specific Water Conditions . . . . . . . . . . . . . . . . . . . . . . . . .8-8

Table 8.5. Preparing a 200-ppm Chlorine Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-9

Table 8.6. Analyzing and Correcting Water Quality Problems . . . . . . . . . . . . . . . . . . . . . . . . .8-11

Healthy Housing Reference Manual 1

Contents
“We never know the worth of water till the well is dry.”

Thomas Fuller

Gnomologia, 1732

Introduction

One of the primary differences between rural and urban

housing is that much infrastructure that is often taken

for granted by the urban resident does not exist in the

rural environment. Examples range from fire and police

protection to drinking water and sewage disposal. This

chapter is intended to provide basic knowledge about the

sources of drinking water typically used for homes in the

rural environment. It is estimated that at least 15% of

the population of the United States is not served by

approved public water systems. Instead, they use individual

wells and very small drinking water systems not covered

by the Safe Water Drinking Act (SDWA); these wells and

systems are often untested and contaminated [1]. Many

of these wells are dug rather than drilled. Such shallow

sources frequently are contaminated with both chemicals

and bacteria. Figure 8.1 shows the change in water

supply source in the United States from 1970 to 1990.

According to the 2003 American Housing Survey, of the

105,843,000 homes in the United States, water is

provided to 92,324,000 (87.2%) by a public or private

business; 13,097,000 (12.4%) have a well (11,276,000

drilled, 919,000 dug, and 902,000 not reported) [3].

Water Sources

The primary sources of drinking water are groundwater

and surface water. In addition, precipitation (rain and

snow) can be collected and contained. The initial quality

of the water depends on the source. Surface water (lakes,

reservoirs, streams, and rivers), the drinking water source

for approximately 50% of our population, is generally of

poor quality and requires extensive treatment.

Groundwater, the source for the other approximately

50% of our population, is of better quality. However, it

still may be contaminated by agricultural runoff or

surface and subsurface disposal of liquid waste, including

leachate from solid waste landfills. Other sources, such as

spring water and rain water, are of varying levels of quality,

but each can be developed and treated to render it potable. 

Most water systems consist of a water source (such as a

well, spring, or lake), some type of tank for storage, and

a system of pipes for distribution. Means to treat the

water to remove harmful bacteria or chemicals may also be

required. The system can be as simple as a well, a pump,

and a pressure tank to serve a single home. It may be a

complex system, with elaborate treatment processes,

multiple storage tanks, and a large distribution system

serving thousands of homes. Regardless of system size,

the basic principles to assure the safety and potability of

water are common to all systems. Large-scale water

supply systems tend to rely on surface water resources,

and smaller water systems tend to use groundwater. 

Groundwater is pumped from wells drilled into aquifers.

Aquifers are geologic formations where water pools, often

deep in the ground. Some aquifers are actually higher

than the surrounding ground surface, which can result in

flowing springs or artesian wells. Artesian wells are often

Chapter 8: Rural Water Supplies and Water-quality Issues

Healthy Housing Reference Manual 8-1

Figure 8.1. U.S. Water Supply by Source [2]
drilled; once the aquifer is penetrated, the water flows

onto the surface of the ground because of the hydrologic

pressure from the aquifer.

SDWA defines a public water system as one that provides

piped water to at least 25 persons or 15 service connections

for at least 60 days per year. Such systems may be owned

by homeowner associations, investor-owned water

companies, local governments, and others. Water not

from a public water supply, and which serves one or only

a few homes, is called a private supply. Private water

supplies are, for the most part, unregulated. Community

water systems are public systems that serve people yearround in their homes. The U.S. Environmental Protection

Agency (EPA) also regulates other kinds of public water

systems-such as those at schools, factories, campgrounds,

or restaurants-that have their own water supply. 

The quantity of water in an aquifer and the water

produced by a well depend on the nature of the rock,

sand, or soil in the aquifer where the well withdraws

water. Drinking water wells may be shallow (50 feet or

less) or deep (more than 1,000 feet). 

On average, our society uses almost 100 gallons of

drinking water per person per day. Traditionally, water use

rates are described in units of gallons per capita per day

(gallons used by one person in 1 day). Of the drinking

water supplied by public water systems, only a small

portion is actually used for drinking. Residential water

consumers use most drinking water for other purposes,

such as toilet flushing, bathing, cooking, cleaning, and

lawn watering. 

The amount of water we use in our homes varies during

the day: 

• Lowest rate of use—11:30 PM to 5:00 AM,

• Sharp rise/high use—5:00 AM to noon (peak

hourly use from 7:00 AM to 8:00 AM),

• Moderate use—noon to 5:00 PM (lull around

3:00 PM), and 

• Increasing evening use—5:00 PM to 11:00 PM

(second minor peak, 6:00 PM to 8:00 PM). 

Source Location

The location of any source of water under consideration

as a potable supply, whether individual or community,

should be carefully evaluated for potential sources of

contamination. As a general practice, the maximum

distance that economics, land ownership, geology, and

topography will allow should separate a water source from

potential contamination sources. Table 8.1 details some of

the sources of contamination and gives minimum

distances recommended by EPA to separate pollution

sources from the water source.

Water withdrawn directly from rivers, lakes, or reservoirs

cannot be assumed to be clean enough for human

consumption unless it receives treatment. Water pumped

from underground aquifers will require some level of

treatment. Believing surface water or soil-filtered water

has purified itself is dangerous and unjustified. Clear

water is not necessarily safe water. To assess the level of

treatment a water source requires, follow these steps:

• Determine the quality needed for the intended

purpose (drinking water quality needs to be

evaluated under the SDWA).

• For wells and springs, test the water for

bacteriologic quality. This should be done with

several samples taken over a period of time to

8-2 Rural Water Supplies and Water-quality Issues

Table 8.1. Recommended Minimum Distance Between Well and Pollution Sources (Horizontal Distance) [1]
establish a history on the source. With few

exceptions, surface water and groundwater sources

are always presumed to be bacteriologically unsafe

and, as a minimum, must be disinfected.

• Analyze for chemical quality, including both legal

(primary drinking water) standards and aesthetic

(secondary) standards.

• Determine the economical and technical restraints

(e.g., cost of equipment, operation and

maintenance costs, cost of alternative sources,

availability of power).

• Treat if necessary and feasible.

Well Construction

Many smaller communities obtain drinking water solely

from underground aquifers. In addition, according to the

last census with data on water supply systems, 15% of

people in the United States are on individual water supply

systems. In some sections of the country, there may be a

choice of individual water supply sources that will supply

water throughout the year. Some areas of the country may

be limited to one source. The various sources of water

include drilled wells, driven wells, jetted wells, dug wells,

bored wells, springs, and cisterns. Table 8.2 provides a

more detailed description of some of these wells.

Regardless of the choice for a water supply source, special

safety precautions must be taken to assure the potability

of the water. Drainage should be away from a well. The

casings of the well should be sealed with grout or some other

mastic material to ensure that surface water does not seep

along the well casing to the water source. In Figure 8.2,

the concrete grout has been reinforced with steel and a

drain away from the casing has been provided to assist in

protecting this water source. Additionally, research

suggests that a minimum of 10 feet of soil is essential to

filter unwanted biologic organisms from the water source. 

However, if the area of well construction has any sources

of chemical contamination nearby, the local public health

authority should be contacted. In areas with karst

topography (areas characterized by a limestone landscape

with caves, fissures, and underground streams), wells of

any type are a health risk because of the long distances

that both chemical and biologic contaminants can travel. 

When determining where a water well is to be located,

several factors should be considered:

• the groundwater aquifer to be developed, 

• depth of the water-bearing formations, 

• the type of rock formations that will be encountered, 

• freedom from flooding, and 

• relation to existing or potential sources 

of contamination. 

Figure 8.2. Cross Section of a Driven Well

Table 8.2. Types of Wells for Accessing Groundwater, Well Depths, and Diameters

Healthy Housing Reference Manual 8-3
The overriding concern is to protect any kind of well

from pollution, primarily bacterial contamination.

Groundwater found in sand, clay, and gravel formations is

more likely to be safer than groundwater extracted from

limestone and other fractured rock formations. Whatever

the strata, wells should be protected from

• surface water entering directly into the top of the well, 

• groundwater entering below ground level without

filtering through at least 10 feet of earth, and 

• surface water entering the space between the well

casing and surrounding soil.

Also, a well should be located in such a way that it is

accessible for maintenance, inspection, and pump or pipe

replacement when necessary. Driven wells (Figure 8.2) are

typically installed in sand or soil and do not penetrate

base rock. They are, as a result, hammered into the ground

and are quite shallow, resulting in frequent contamination by

both chemical and bacterial sources. 

Sanitary Design and Construction 

Whenever a water-bearing formation is penetrated (as in

well construction), a direct route of possible water

contamination exists unless satisfactory precautions are

taken. Wells should be provided with casing or pipe to an

adequate depth to prevent caving and to permit sealing of

the earth formation to the casing with watertight cement

grout or bentonite clay, from a point just below the

surface to as deep as necessary to prevent entry of

contaminated water. 

Once construction of the well is completed, the top of the

well casing should be covered with a sanitary seal, an

approved well cap, or a pump mounting that completely

covers the well opening (Figure 8.3). If pumping at the

design rate causes drawdown in the well, a vent through a

tapped opening should be provided. The upper end of the

vent pipe should be turned downward and suitably

screened to prevent the entry of insects and foreign matter. 

Pump Selection

A variety of pump types and sizes exist to meet the needs

of individual or community water systems. Some of the

factors to be considered in selecting a pump for a specific

application are well depth, system design pressure,

demand rate in gallons per minute, availability of power,

and economics. 

Dug and Drilled Wells

Dug wells (Figures 8.4 and 8.5) were one of the most

common types of wells for individual water supply in the

United States before the 1950s. They were often

constructed with one person digging the hole with a

shovel and another pulling the dirt from the hole with a

rope, pulley, and bucket. Of course, this required a hole

of rather large circumference, with the size increasing the

potential for leakage from the surface. The dug well also

was traditionally quite shallow, often less than 25 feet,

which often resulted in the water source being

8-4 Rural Water Supplies and Water-quality Issues

Figure 8.3. Well Seal Figure 8.4. Converted Dug Well [1]
contaminated by surface water as it ran through cracks

and crevices in the ground to the aquifer. Dug wells

provide potable water only if they are properly located

and the water source is free of biologic and chemical

contamination. The general rule is, the deeper the well,

the more likely the aquifer is to be free of contaminants,

as long as surface water does not leak into the well

without sufficient soil filtration. 

Two basic processes are used to remediate dug wells. One

is to dig around the well to a depth of 10 feet and install

a solid slab with a hole in it to accommodate a well casing

and an appropriate seal (Figures 8.4 and 8.5). The dirt is

then backfilled over the slab to the surface, and the casing

is equipped with a vent and second seal, similar to a

drilled well, as shown in Figure 8.6. This results in a

considerable reduction in the area of the casing that needs

to be protected. Experience has shown that the disturbed

dirt used for backfilling over the buried slab will continue

to release bacteria into the well for a short time after

modification. Most experts in well modification suggest

installing a chlorination system on all dug wells to

disinfect the water because of their shallow depth and

possible biologic impurity during changing drainage and

weather conditions above ground. Figure 8.7 shows a dug

well near the front porch of a house and within 5 feet of a

drainage ditch and 6 feet of a rural road. This well is

likely to be contaminated with the pesticide used to

termite-proof the home and from whatever runs off the

nearby road and drainage ditch. The well shown is about

15 feet deep. The brick structure around the well holds

the centrifugal pump and a heater to keep the water from

freezing. Although dangerous to drink from, this well is

Healthy Housing Reference Manual 8-5

Figure 8.5. Recapped and Sealed Dug Well [1]

Figure 8.6. Drilled Well [4]

Figure 8.7. Typical Dug Well
typical of dug wells used in rural areas of the United

States for drinking water. 

Samples should not be taken from such wells because they

instill a false sense of security if they are negative for both

chemicals and biologic organisms. The quality of the

water in such wells can change in just a few hours

through infiltration of drainage water. Figure 8.8 shows

the septic tank discharge in the drainage ditch 5 feet

upstream of the dug well in Figure 8.7. This potential

combination of drinking water and waste disposal presents

an extreme risk to the people serviced by the dug well.

Sampling is not the answer; the water source should be

changed under the supervision of qualified environmental

health professionals.

Figure 8.9 shows a drilled well. On the left side of the picture

is the corner of the porch of the home. The well appears

not to have a sanitary well seal and is likely open to the

air and will accept contaminants into the casing. Because the

well is so close to the house, the casing is open, and the land

slopes toward the well, it is a major candidate for

contamination and not a safe water source. 

Springs 

Another source of water for individual water supply is

natural springs. A spring is groundwater that reaches the

surface because of the natural contours of the land. 

Springs are common in rolling hillside and mountain

areas. Some provide an ample supply of water, but most

provide water only seasonally. Without proper precautions, the

water may be biologically or chemically contaminated and

not considered potable. 

To obtain satisfactory (potable) water from a spring, it is

necessary to

• find the source,

• properly develop the spring,

• eliminate surface water outcroppings above the

spring to its source,

• prevent animals from accessing the spring area, and

• provide continuous chlorination.

Figure 8.10 illustrates a properly developed spring. Note

that the line supplying the water is well underground, the

spring box is watertight, and surface water runoff is

diverted away from the area. Also be aware that the water

quality of a spring can change rapidly.

Cisterns

A cistern is a watertight, traditionally underground

reservoir that is filled with rainwater draining from the

8-6 Rural Water Supplies and Water-quality Issues

Figure 8.10. Spring Box [5]

Figure 8.8. Sewage in Drainage Ditch

Figure 8.9. Drilled Well
roof of a building. Cisterns will not provide an ample

supply of water for any extended period of time, unless

the amount of water used is severely restricted. Because

the water is coming off the roof, a pipe is generally

installed to allow redirection of the first few minutes of

rainwater until the water flows clear. Disinfection is,

nevertheless, of utmost importance. Diverting the first

flow of water does not assure safe, non-polluted water

because chemicals and biologic waste from birds and other

animals can migrate from catchment surfaces and from

windblown sources. In addition, rainwater has a low pH,

which can corrode plumbing pipes and fixtures if not treated.

Disinfection of Water Supplies

Water supplies can be disinfected by a variety of methods

including chlorination, ozonation, ultraviolet radiation,

heat, and iodination. The advantages and disadvantages of

each method are noted in Table 8.3. 

The understanding of certain terms (blue box, next page)

is necessary in talking about chlorination. 

Table 8.4 is a chlorination guide for specific water conditions.

Chlorine is the most commonly used water disinfectant.

It is available in liquid, powder, gas, and tablet form.

Chlorine gas is often used for municipal water

disinfection, but can be hazardous if mishandled.

Recommended liquid, powder, and tablet forms of

chlorine include the following:

• Liquid—Chlorine laundry bleach (about 5%

chlorine). Swimming pool disinfectant or

concentrated chlorine bleach (12%–17% chlorine).

• Powder—Chlorinated lime (25% chlorine), dairy

sanitizer (30% chlorine), and high-test calcium

hypochlorite (65%–75% chlorine). 

Table 8.3. Disinfection Methods 

Healthy Housing Reference Manual 8-7
8-8 Rural Water Supplies and Water-quality Issues

Table 8.4. Chlorination Guide for Specific Water Conditions 

Breakpoint chlorination—A process sometimes used to ensure the presence of free chlorine in public water supplies by

adding enough chlorine to the water to satisfy the chlorine demand and to react with all dissolved ammonia that might

be present. The concentrations of chlorine needed to treat a variety of water conditions are listed in Table 8.4. 

Chlorine concentration—The concentration (amount) of chlorine in a volume of water is measured in parts per million

(ppm). In 1 million gallons of water, a chlorine concentration of 1 ppm would require 8.34 pounds of 100% chlorine.

Contact time—The time, after chlorine addition and before use, given for disinfection to occur. For groundwater systems,

contact time is minimal. However, in surface water systems, a contact time of 20 to 30 minutes is common.

Dosage—The total amount of chlorine added to water. Given in parts per million (ppm) or milligrams per liter

(mg/L).

Demand—Chlorine solution used by reacting with particles of organic matter such as slimes or other chemicals and

minerals that may be present. The difference between the amount of chlorine applied to water and total available

chlorine remaining at the end of a specified contact period.

Parts per million—A weight-to-weight comparison; 1 ppm equals 1 pound per million pounds. Because water weighs

8.34 pounds per gallon, it takes 8.34 pounds of any substance per million gallons to equal 1 ppm. In water chemistry,

1 ppm equals 1 mg/L.

Residual—The amount of chlorine left after the demand is met; available (free) chlorine. This portion provides a ready

reserve for bactericidal action. Both combined and free chlorine make up chlorine residual and are involved in disinfection.

Total available chlorine = free chlorine + combined chlorine.

Definitions of Terms Related to Chlorination
• Tablets—High-test calcium hypochlorite

(65%–75% chlorine).

• Gas—Gas chlorine is an economical and

convenient way to use large amounts of chlorine.

It is stored in steel cylinders ranging in size from

100 to 2,000 pounds. The packager fills these

cylinders with liquid chlorine to approximately

85% of their total volume; the remaining 15% is

occupied by chlorine gas. These ratios are required

to prevent tank rupture at high temperatures. It is

important that direct sunlight never reaches gas

cylinders. It is also important that the user of

chlorine knows the maximum withdrawal rate of

gas per day per cylinder. For example, the

maximum withdrawal rate from a 150-pound

cylinder is approximately 40 pounds per day at room

temperature discharging to atmospheric pressure.

Chlorine Carrier Solutions

On small systems or individual wells, a high-chlorine carrier

solution is mixed in a tank in the pump house and pumped

by the chlorinator into the system. Table 8.5 shows how

to make a 200-ppm carrier solution. By using 200 ppm,

only small quantities of this carrier have to be added.

Depending on the system, other stock solutions may be

needed to better use existing chemical feed equipment.

Routine Water Chlorination (Simple)

Most chlorinated public water supplies use routine water

chlorination. Enough chlorine is added to the water to

meet the chlorine demand, plus enough extra to supply

0.2 to 0.5 ppm of free chlorine when checked after 20 minutes.

Simple chlorination may not be enough to kill certain

viruses. Chlorine as a disinfectant increases in

effectiveness as the chlorine residual is increased and as

the contact time is increased. 

Chlorine solutions should be mixed and chlorinators

adjusted according to the manufacturer’s instructions.

Chlorine solutions deteriorate gradually when standing.

Fresh solutions must be prepared as necessary to maintain

the required chlorine residual. Chlorine residual should be

tested at least once a week to assure effective equipment

operation and solution strengths. 

A dated record should be kept of solution preparation,

type, proportion of chlorine used, and residual-test results.

Sensing devices are available that will automatically shut off

the pump and activate a warning bell or light when the

chlorinator needs servicing. 

Well Water Shock Chlorination

Shock chlorination is used to control iron and sulfatereducing bacteria and to eliminate fecal coliform bacteria

in a water system. To be effective, shock chlorination

must disinfect the following: the entire well depth, the

formation around the bottom of the well, the pressure

system, water treatment equipment, and the distribution

system. To accomplish this, a large volume of superchlorinated water is siphoned down the well to displace

the water in the well and some of the water in the

formation around the well. Check specifications on the

water treatment equipment to ensure appropriate protection

of the equipment.

With shock chlorination, the entire system-from the

water-bearing formation through the well-bore and the

distribution system-is exposed to water that has a concentration

of chlorine strong enough to kill iron and sulfate-reducing

bacteria. The shock chlorination process is complex and

tedious. Exact procedures and concentrations of chlorine

for effective shock treatment are available [6,7].

Backflow, Back-siphonage, and Other Water

Quality Problems

In addition to contamination at its source, water can

become contaminated with biologic materials and toxic

construction or unsuitable joint materials as it flows

through the water distribution system in the home. Water

flowing backwards (backflow) in the pipes sucks materials

back (back-siphonage) into the water distribution system,

creating equally hazardous conditions. Other water quality

problems relate to hardness, dissolved iron and iron bacteria,

acidity, turbidity, color, odor, and taste.

Backflow

Backflow is any unwanted flow of nonpotable water into

a potable water system. The direction of flow is the

reverse of that intended for the system. Backflow may be

caused by numerous factors and conditions. For example,

the reverse pressure gradient may be a result of either a

loss of pressure in the supply main (back-siphonage) or

the flow from a pressurized system through an unprotected

Healthy Housing Reference Manual 8-9

Table 8.5. Preparing a 200-ppm Chlorine Solution 
cross-connection (back-pressure). A reverse flow in a

distribution main or in a customer’s system can be created

by a change of system pressure wherein the pressure at the

supply point becomes lower than the pressure at the point

of use. When this happens, the water at the point of use

will be siphoned back into the system, potentially

polluting or contaminating it. It is also possible that

contaminated or polluted water could continue to

backflow into the public distribution system. The point at

which nonpotable water comes in contact with potable

water is called a cross-connection. 

Examples of backflow causes include supplemental

supplies, such as a standby fire protection tank; fire

pumps; chemical feed pumps that overpower the potable

water system pressure; and sprinkler systems.

Back-Siphonage

Back-siphonage is a siphon action in an undesirable or

reverse direction. When there is a direct or indirect

connection between a potable water supply and water of

questionable quality due to poor plumbing design or

installation, there is always a possibility that the public

water supply may become contaminated. Some examples

of common plumbing defects are

• washbasins, sterilizers, and sinks with submerged

inlets or threaded hose bibs and hose;

• oversized booster pumps that overtax the supply

capability of the main and thus develop negative

pressure;

• submerged inlets and fire pumps (if the fire

pumps are directly connected into the water main,

a negative pressure will develop); and

• a threaded hose bib in a health-care facility (which

is technically a cross-connection). 

There are many techniques and devices for preventing 

back-flow and back-siphonage. Some examples are

• Vacuum breakers (nonpressure and pressure);

• Back-flow preventers (reduced pressure principle,

double gate-double check valves, swingconnection, and air gap-double diameter

separation);

• Surge tanks (booster pumps for tanks, fire system

make-up tank, and covering potable tanks); and 

• Color coding in all buildings where there is any

possibility of connecting two separate systems or

taking water from the wrong source (blue-potable,

yellow-nonpotable, and other-chemical and gases).

An air gap is a physical separation between the incoming

water line and maximum level in a container of at least

twice the diameter of the incoming water line. If an air

gap cannot be installed, then a vacuum breaker should be

installed. Vacuum breakers, unlike air gaps, must be

installed carefully and maintained regularly. Vacuum

breakers are not completely failsafe. 

Other Water Quality Problems

Water not only has to be safe to drink; it should also be

aesthetically pleasing. Various water conditions affect

water quality. Table 8.6 describes symptoms, causes,

measurements, and how to correct these problems.

Protecting the Groundwater Supply 

Follow these tips to help protect the quality of

groundwater supplies:

• Periodically inspect exposed parts of wells for

cracked, corroded, or damaged well casings;

broken or missing well caps; and settling and

cracking of surface seals.

• Slope the area around wells to drain surface runoff

away from the well.

• Install a well cap or sanitary seal to prevent

unauthorized use of, or entry into, a well.

• Disinfect wells at least once a year with bleach or

hypochlorite granules, according to the

manufacturer’s directions.

• Have wells tested once a year for coliform bacteria,

nitrates, and other constituents of concern.

• Keep accurate records of any well maintenance,

such as disinfection or sediment removal, that

require the use of chemicals in the well.

• Hire a certified well driller for new well construction,

modification, or abandonment and closure.

• Avoid mixing or using pesticides, fertilizers,

herbicides, degreasers, fuels, and other pollutants

near wells.

• Do not dispose of waste in dry or abandoned wells.

8-10 Rural Water Supplies and Water-quality Issues
• Do not cut off well casings below the land

surface.

• Pump and inspect septic systems as often as

recommended by local health departments.

• Never dispose of hazardous materials (e.g., paint,

paint stripper, floor stripper compounds) in a

septic system.

References

1. Rhode Island Department of Health and 

University of Rhode Island Cooperative Extension

Water Quality Program. Healthy drinking waters 

for Rhode Islanders. Kingston, RI: Rhode Island 

Department of Health and University of Rhode 

Island Cooperative Extension Water Quality 

Program; 2003. Available from URL: 

http://www.uri.edu/ce/wq/has/html/Drinking.pdf.

Healthy Housing Reference Manual 8-11

Table 8.6. Analyzing and Correcting Water Quality Problems (continues on next page)
2. US Census Bureau. Historical census of housing 

graphs: water supply. Washington, DC: US 

Census Bureau; no date. Available from URL: 

http://www.census.gov/hhes/www/housing/ 

census/historic/swgraph.html.

3. US Census Bureau. American housing survey. 

Washington, DC: US Census Bureau; 2003. 

Available from URL: http://www.census.gov/hhes/

www/housing/ahs/nationaldata.html.

4. National Ground Water Association. Well system 

material. Westerville, OH: National Ground 

Water Association; 2003. Available from URL: 

http://www.ngwa.org/pdf/wellsystemmaterials.pdf.

5. US Environmental Protection Agency. Spring 

development. Chicago: US Environmental 

Protection Agency; 2001. 

6. Government of Alberta. Shock chlorination—well

maintenance. Edmonton, Alberta, Canada: Alberta 

Agriculture, Food & Rural Development;2001.

Available from URL: http://www1.agric.gov.ab.ca/

$department/deptdocs.nsf/all/wwg411.

7. Boulder GNS Water Well Service and Supply. 

Chlorination of water systems. Boulder, CO: 

Boulder GNS Water Well Service and Supply; 

2002. Available from URL: http://www.waterwell.cc/

CHLORIN.HTM.

8. Iowa State University Diagnosing and solving 

common water-quality problems. Ames, IA: Iowa 

State University; 1994. Available from URL: 

http://www.abe.iastate.edu/HTMDOCS/

aen152.pdf.

Additional Sources of Information

American Water Works Association. Available from URL:

http://www.awwa.org.

Drexel University: Drinking water outbreaks. Available

from URL: http://water.sesep.drexel.edu/outbreaks/.

US Environmental Protection Agency: Ground water and

drinking water. Available from URL:

http://www.epa.gov/safewater. 

8-12 Rural Water Supplies and Water-quality Issues

Table 8.6. Analyzing and Correcting Water Quality Problems (continued)