Recirculating plumbing system

A water conservation and delivery system for a building includes a first subsystem for dispensing clean water from a faucet, a second subsystem for draining waste water from the vessel supplied by the faucet, and a third subsystem for recirculating clean water prior to dispensement back into the dispensing subsystem while the dispensing temperature and flow are adjusted.

FIELD OF THE INVENTION 
This invention relates to water delivery systems for buildings and 
vehicles. More specifically, the invention relates to a system that 
recirculates for later use water that is hotter or colder than currently 
desired. 
BACKGROUND OF THE INVENTION 
Conventional plumbing systems are wasteful; they waste water and they waste 
the energy used to heat the water. For example, when a person tests or 
adjusts the temperature of water dispensed from a faucet, water that is 
too cold or too hot is generally spilled down the drain and wasted. A 
utility expended resources to acquire, store, treat, and deliver that 
water; the building owner paid money to buy and heat that water. 
When such wastage occurs throughout a whole building or a whole utility, 
the losses are significant. Reducing such wastage would decrease expenses 
for landlords and hoteliers, and would allow utilities to build smaller 
reservoir, treatment and delivery systems for a given number of customers. 
In areas where water is scarce, a reduction in wastage might lead to a 
reduction in rationing. A system for reducing wastage might similarly find 
advantageous use on planes, boats and recreational vehicles that carry 
water subject to weight or space limitations. 
The fundamental disadvantage in a conventional plumbing system is that it 
has only two types of pipes: incoming pipes for delivering clean water and 
outgoing pipes for removing waste water. Clean water dispensed at an 
incorrect temperature has no place to go except down the drain with the 
waste water. What is needed is a plumbing system that provides for 
recirculation of clean water dispensed at the wrong temperature. 
The present invention is directed to such a system. 
SUMMARY OF THE INVENTION 
According to one aspect of the invention there is provided a system for 
supplying a mixture of fluid from first and second sources to a 
consumption device comprising: a mixing vessel having: a mixing chamber, a 
first valved inlet adapted to receive fluid from the first source for 
mixing in the mixing chamber, a second valved inlet adapted to receive 
fluid from the second source for mixing in the mixing chamber, and a first 
valved outlet adapted to dispense fluid mixed in the mixing chamber into 
the consumption device, as well as means for sensing the temperature of 
the fluid mixture inside the mixing chamber, and means for controlling the 
first valved inlet responsive to the temperature sensing means. The system 
might further include means for controlling the second valved inlet 
responsive to the temperature sensing means, means for sensing the rate of 
flow of fluid through the first valved outlet, and means for controlling 
the first valved outlet responsive to the flow rate sensing means. The 
system might also include means for sensing the amount of fluid dispensed 
into the consumption device where such means might be a fluid level 
detector or a timer. The system could further include means for 
controlling the first valved outlet responsive to the amount sensing means 
and such controlling means can include a microprocessor. The system might 
further include a holding tank, wherein the mixing vessel further includes 
a second valved outlet adapted to discharge water into the holding device. 
The system might include means for controlling the second valved outlet 
responsive to the temperature sensing means and means for reinjecting 
fluid from the holding tank into the first source. The reinjecting means 
might include a pump connected to draw fluid from the holding tank toward 
the first source, a check valve connected to receive fluid from the 
holding tank and to supply the fluid to the first source, means for 
controlling the pump responsive to the fluid level in the holding tank 
which pump controlling means might be a microprocessor, means for 
controlling the pump responsive to the fluid pressure at the first source, 
and means for damping pressure transients where the pressure damping means 
might be a pressure accumulator. 
According to another aspect of the invention, there is provided a method of 
supplying a mixture of fluid from first and second sources to a 
consumption device comprising: connecting a mixing vessel having a mixing 
chamber with a first valved inlet, a second valved inlet, and a first 
valved outlet to the first and second sources and the consumption device 
such that: the first valved inlet receives fluid from the first source for 
mixing in the mixing chamber, the second valved inlet receives fluid from 
the second source for mixing in the mixing chamber, and the first valved 
outlet dispenses fluid mixed in the mixing chamber into the consumption 
device, sensing the temperature of the fluid mixture inside the mixing 
chamber, and controlling the first valved inlet responsive to the 
temperature in the mixing chamber. The method might include controlling 
the second valved inlet responsive to the temperature in the mixing 
chamber, sensing the rate of flow of fluid through the first valved 
outlet, controlling the first valved outlet responsive to the flow rate, 
sensing the amount of fluid dispensed into the consumption device, and 
controlling the first valved outlet responsive to the amount of fluid 
dispensed into the consumption device. The method might further include 
connecting a second valved outlet in the mixing chamber to a holding tank 
such that second valved outlet discharges fluid mixed in the mixing 
chamber into the holding tank. The method might include controlling the 
second valved outlet responsive to the temperature in the mixing chamber, 
and reinjecting fluid from the holding tank into the first source, wherein 
the reinjecting step is executed with a pump connected to draw fluid from 
the holding tank toward the first source. The method might include 
controlling the pump responsive to the fluid level in the holding tank, 
and controlling the pump responsive to the fluid pressure at the first 
source, and damping pressure transients between the pump and the first 
source.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
With reference now to the drawing, a plumbing system 100 embodying one 
aspect of the invention includes a supply subsystem generally illustrated 
at 200, a mixing subsystem generally illustrated at 300 connected to 
receive water from the supply subsystem 200, a consumption subsystem 
generally illustrated at 400 connected to receive water from the mixing 
subsystem 300, and a recirculation subsystem generally illustrated at 500 
connected to receive water from the mixing subsystem 300 and to 
recirculate it into the supply subsystem 200. 
The supply subsystem 200 begins at a cold water inlet 210 which is 
connected to receive water from the mains. The cold water inlet 210 feeds 
a cold water line 212. The cold water inlet 210 also feeds a water heater 
214 through a heater valve 216. The water heater 214 in turn feeds a hot 
water line 218. 
The mixing subsystem 300 is formed around a mixing chamber 310. The mixing 
chamber 310 is connected to receive cold water from the cold water line 
212 through a cold water inlet valve 312 and connected to receive hot 
water from the hot water line 218 through a hot water inlet valve 314. As 
will be described further under system operation, the mixing chamber 310 
is connected to dispense water into the consumption subsystem 400 through 
a dispensing valve 316 and connected to discharge water into the 
recirculation subsystem 500 through a recirculation valve 318. 
The mixing subsystem 300 is controlled by a mixing microprocessor 320. The 
mixing microprocessor 320 is connected to receive information signals from 
a temperature sensor 322 in the mixing chamber 310, from a flow sensor 324 
at the dispensing valve 316, from a quantity sensor 326, such as a fluid 
level detector, at the consumption subsystem 400 and from an operator 
keypad 328. The mixing microprocessor 320 is connected to control the cold 
water input valve 312, the hot water input valve 314, the output valve 316 
and the recirculation valve 318. 
The consumption subsystem 400 includes a consumption device 410 such as a 
sink, a tub or a shower which has an inlet port 412 connected to receive 
water from the mixing subsystem 300 dispensing valve 316. The consumption 
device 410 might also include a hot water bypass valve 414 connected to 
receive water directly from the hot water line 218 and a cold water bypass 
valve 416 connected to receive water directly from the cold water line 212 
without engaging the mixing subsystem 300. These bypass valves 412, 416 
would be normally closed but could be opened to operate the consumption 
device 410 when the mixing subsystem 300 was not operational. 
The recirculation subsystem 500 includes an insulated holding tank 510 that 
is connected to receive water from the mixing subsystem 300 recirculation 
valve 318. The holding tank 510 includes a reinjection outlet 512 as well 
as an emergency overflow outlet 514. The reinjection outlet 512 is 
connected to feed the hot water heater 214 via a reinjection pump 516, a 
check valve 518, and a pressure accumulator 520. A recirculation 
microprocessor 522 is connected to receive information signals from a 
maximum level sensor 524 and a minimum level sensor 526 in the holding 
tank 510, and from a line pressure sensor 528 between the check valve 518 
and the pressure accumulator 520. The recirculation microprocessor 522 is 
connected to control the reinjection pump 516 and the heater valve 216. 
In operation, the operator uses the keypad 328 to instruct the mixing 
microprocessor 320 to dispense water to the consumption device 410. The 
operator can select such characteristics for the water as temperature, 
quantity, flow rate, or flow duration. The mixing microprocessor 320 opens 
the cold water input valve 312 and/or the hot water input valve 314 to 
bring water into the mixing chamber 310 in approximately the right 
proportion to achieve the temperature selected. If the temperature sensor 
322 indicates that the water mixture inside the mixing chamber 310 is not 
at the temperature selected by the operator, the mixing microprocessor 320 
adjusts the cold water input valve 312 and/or the hot water input valve 
314 as needed and opens the recirculation valve 318 to discharge the water 
mixture* into the recirculation subsystem 500 for later use. If the 
temperature sensor 322 indicates that the water mixture inside the mixing 
chamber 310 is at the temperature selected by the operator, the mixing 
microprocessor 320 closes the recirculation valve 318 and opens the 
dispensing valve 316, thereby allowing the mixed water to flow into the 
consumption subsystem 400. The flow sensor 324 at the dispensing valve 316 
and the quantity sensor 326 at the consumption device 410 provide the 
mixing microprocessor with the information needed to adjust the dispensing 
valve 316 such that the right amount of water is dispensed for the right 
amount of time at the right pressure. 
Recirculated water is stored in the insulated holding tank 510 for 
subsequent reinjection into the hot water tank 214. When the water in the 
holding tank 510 rises above a maximum preset level, the maximum level 
sensor 524 informs the recirculation microprocessor 522. The recirculation 
microprocessor 522 closes the heater valve 216 to isolate the hot water 
tank 214 from the mains and then checks the pressure sensor 528 to 
determine whether the hot water tank 214 is already filled to capacity. If 
so, the recirculation microprocessor 522 will continue to monitor the 
recirculation system 500 but will not engage any device. If the holding 
tank 510 continues to fill under such conditions, excess water may 
eventually spill from the emergency overflow outlet 514. 
When the pressure sensor 528 indicates to the recirculation microprocessor 
522 that the hot water tank 214 can accept water, the recirculation 
microprocessor 522 turns on the reinjection pump 516. The reinjection pump 
516 discharges water from the holding tank 510 through the check valve 518 
into the hot water tank 214 via the pressure accumulator 520. Water being 
incompressible, the pressure accumulator 520 is used as a means to 
discourage the line pressure from increasing rapidly the moment the pump 
516 is engaged. If the line pressure were allowed to rise unchecked, the 
pressure sensor 528 would detect falsely that the hot water tank 214 was 
full and would incorrectly indicate to the recirculation microprocessor 
522 that the pump 516 must be stopped immediately after it is started. 
When the pressure sensor 528 indicates to the recirculation microprocessor 
522 that the hot water tank 214 is full, the recirculation microprocessor 
522 stops the reinjection pump 516. When the minimum level sensor 526 
indicates to the recirculation microprocessor 522 that the water level in 
the holding tank 510 has fallen below a minimum level, the recirculation 
microprocessor 522 stops the reinjection pump 516 and opens the heater 
valve 216 to reconnect the hot water tank 214 to the mains. 
Although a specific embodiment of the present invention has been described 
and illustrated, the present invention is not limited to the features of 
this embodiment, but includes all variations and modifications within the 
scope of the claims. 
For example, it is contemplated that more than one consumption subsystem 
400 could be connected to the system 100. 
It is also contemplated that either microprocessor 320, 522 could be 
replaced by other electronic control devices or even a mechanical 
equivalent. For example, much of the functionality of the mixing 
microprocessor 320 could be achieved by a set of mechanical thermostats. 
It is further contemplated that the recirculation subsystem 500 could be 
easily adapted to work with gravity fed plumbing systems such as those 
commonly found in parts of Europe and the United Kingdom. In particular, 
the expansion tank could function directly as the holding tank 510 so that 
the recirculation pump 516 and its accompanying control system would not 
be needed. 
It is still further contemplated that the mixing subsystem 300 could be 
constructed as either an integral part of the consumption device 410 or as 
a retrofitable addition. 
While the preferred embodiment of the invention has been illustrated and 
described, it will be appreciated that various changes can be made therein 
without departing from the spirit and scope of the invention.