Note: Descriptions are shown in the official language in which they were submitted.
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ASPIRATOR WATER CIRCULATION APPARATUS
RACKGROUNI )
This invention relates to quickly providing and ,~A;~ inil~g hot water to remotefaucets in resi(lenti~l and small commercial b~ ing~
The issue being addressed is the waste of water and time running water down the
drain while waiting for hot water from the heater to arrive at remote faucets. In
in~tAllAtions with long pipe runs, such as ranch style homes, this can result in a wait of one
to two minl~tes Tests conducted on a typical ranch style home have shown a waste of 10
to 12 liters of water at each occurrence. In these days of water and energy shortages, the
need to çl;~;n~le this waste has become more acute.
The requirement for a method to quickly provide hot water at remote faucets has
long been known, with devices p~tented in the early years of the twentieth century. These
and subsequent devices were not broadly accepted since they were too complex, their
instAllAtion was diffic llt, or they did not function well. Methods to solve this problem have
generally followed two di~elen~ approaches, (1) water circ~llAtion systems that contim.Qusly
or periodically circulate hot water from the heater to the remote faucet and back to the
heater through a separate return line, and (2) auxiliary remote water heaters, either in the
ba~ement near the faucet, or under the counter at the sink.
One circul~tion approach is convective flow using sloping hot water supply and
return pipes, as shown in U.S. Patent No. 3,929,153 to Hasty, 30 December, 1975, No.
2,255,460 to Weaver, 7 May, 1940 and No. 3,097,661 to Lee, 16 July, 1963. These
systems are fimction~l~ but are in.~en~itive to user needs, circul~ting hot water at all times,
even at night and when inh~bit~nt$ are away. Sloping pipes are easily in~t~lled in new
construction, but are difficult in e~istin~ b~lildin~ . The return pipe must be of a di~meter
ess~nti~lly equal to the supply pipe since convective pressure is extremely low, and flow
would be limited with a small return tube. Considerable heat is lost since the surface area of
the return pipe is large and stays hot at all times. These systems also have a tendency to
excessively heat the cold water pipe which causes a sirnilar problem in the cold water
system that they are intended to solve in the hot water system.
Pumps used for hot water circulation as shown in U.S. Patents No. 3,669,351 to
Meier and Carouge, 13 June, 1972 and No. 4,142,515 to Skaats, 6 March,1979 are also
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functional, but require electrical power, wiring, motors, seals, switches, and timers or
thermostats. They may be more suitable for large co,r"l,ercial blliltlings than residPnti~l
applications. Pump operated systems controlled by timers are also in~Pn~itive to user needs
rP,slllting in wasted heat when hot water is not required. Since pumped circulation systems
have many operating parts, reliability will be affected, and m~intP.n~nce could be an issue.
Due to their complexity, initial procurement and in~t~ tion costs are also high.Operational cost will be experienced to power the pump motor, and noise from the pump
may be objectionable to some people.
Auxiliary heaters as shown in U.S. Patent No. 4,236,548 to Howard, 2 December,
1980 can be used to provide instant hot water to remote outlets, however the cost of initial
procurement and inst~ tion is a si~enific~nt drawback. They require connp~ction to gas (and
nP~cess~ y vent stack) or electricity for their energy source. Operational costs will also be
incurred. Heaters made for in~t~ tion under the counter are de~igne(l to serve extremely
hot water (app~ox;~ p~ly 80 to 85 degrees C.) for direct use in coffee, tea or soups without
fu~rther he~ting These heaters usually contain only a small volume of hot water (3 to 5
liters), and con~titute a potential safety hazard due to their eYtreme temperature.
The recently p~tPnted Dual Mode Hot Water Circul~tion Apparatus (U.S. Patent
No. 5,331,996 - 26 July, 1994, to R. G. Ziehm) uses a cold water heat exch~nger to induce
a low rate convective circulation flow, plus an aspirator to supplement the convective flow
with a higher rate circul~tion flow in response to water use in the building. This system
yields excellent results, with hot water immedi~tPly available at any time, day or night. The
length ofthe heat PYch~n~r requires a space 1 to 1.5 meters long at an angle to the
ho"zolllal where the unit can be imt~lled in the water supply pipe. This space may not
always be available. Although the Dual Mode Hot Water Circ~ tion Apparatus performs
extremely well, m~t~ri~l and m~m-f~ -ring costs for it will be higher than for the present
invention.
ORIFCTS ~ AnV~TA('TF.~
The object of this invention is to provide ills~ ly available hot water to remote
faucets in re.sidçnti~l or small commercial buikling~ Additional objects and advantages of
the present invention are as follows:
A. to provide a water circulation unit that conserves water and time;
B. to provide a water circulation unit that is responsive to user needs;
C. to provide a water circulation unit that is self re~ ting;
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.
D. to provide a water circul~tion unit that is simple in design and operation,
E. to provide a water circulation unit that has high reliability;
F. to provide a water circulation unit that p, esenls no safety hazard;
G. to provide a water circulation unit that needs no electrical power or gas;
H. to provide a water circul~tion unit that is quiet in operation;
I. to provide a water circ~ tion unit that is easy to install;
J. to provide a water circulation unit that is economical to purchase;
K. to provide a water circulation unit whose hot water capacity is essçnti~lly
equal to that of the water heater;
RRTF.F T)F.SCRrPTION OF T~IF np~
Figure 1 shows a pictorial sçh~om~tic of the aspirator water circ~ tion unit in a
typical residenti~l inct~ tion
Figure 2 shows a partially sectioned view of the asph~tor water circ~ tioll unit.
Figure 3 shows the exterior configuration of the unit.
nFTATT F.n T)F.~CR~PTION OF T~F ~V~TION
This invention is a water circul~tion unit ct~ncicting of an aspirator and a check valve
in a housing (body), and fittings for inct~ tion into the building cold water pipe and
connection to a small water return line. Referring to Figure 1, the water circ~ tion unit 21
is installed in the building water supply pipe 22 down~llealn ofthe takeoff23 for outside
water outlets and lawn sprinkler systems. The water return line 24 leads from a tee 25
inct~lled in the hot water pipe 26 (inc~ ted for best performance) at the remote faucet 27,
to a fitting on the circulation unit. The unit is capable of wi~ t~-d;llg domçctic water
supply pressures. Each el~mt~-nt of the unit is presented in more detail in the following
paragraphs:
The water return line 24 is a small tube, nominally 1.0 cm outside di~meter, of a
length determined by each inct~ tion. It will typically be inct~lled with flare or
col-lpression fittings.
Referring now to Figure 2, the body 29 is a cylindrical or similar shaped structure
~ constructed of non-corrosive metal or plastic co~ dl;ble with use in potable water systems,
and may be cast, m~hined, or injection molde~l The aspirator 30 and check valve 31 are
integral to the body 29, each having a separate bore. The unit has inlet and outlet pipe
nipples 32 and 33 respectively, compatible with inct~ tion in the cold water pipe in most
domestic or small commercial buildings according to standard plumbing practices. An
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217688g
internal passageway 34 leads from the outlet end ofthe check valve bore 35 to the as~ or
bore 36. This passageway is closed from the exterior by a plug 37 imt~lled in the body 29.
The following PlPm~Pnt~ are located in or ~tt~ched to the body 29:
1. Aspirator: The aspirator 30 is a tapered bore 36 in the body 29 with a conic
section stainless steel nozzle 38 concentrically located in the large end ofthe bore. The
nozle is perm~n~Pntly installed in the inlet pipe nipple 32 that is threaded into the body 29,
which properly positions it in the aspirator bore 36. The nozzle 38 presents a reduced cross
section in the flow stream. The bore 36 forms the walls of a low pressure ch~mbPr 39 in the
vicinity of the nozzle outlet. The passageway 34 in the body from the check valve 31 enters
the aspirator bore 36 into the low pressure chamber 39. Rt;~e-.mg back to Figure 1, the unit
is installed in the cold water supply pipe 22 with the nozzle end toward the water source,
and the outlet end connected to the pipe leading to the water heater 40 and cold water
outlets 41. The flow path is arranged so that all water for the buil~in~ except for outside
water outlets and lawn sprinkler systems, passes through the nozzle.
2. Check Valve: Referring again to Figure 2, the check valve 31 incl~ldes a poppet
42 that is free in a smooth, cylindrical, bore 35 in the body 29, and a concp~ntric valve seat
fitting 28 threaded into the body 29 at the inlet end ofthe bore 35. The poppet 42 has a
cross section other than round, and a valve face on the inlet end that interfaces with the
valve seat 43. The cross section of the poppet 42 is con_gured so that the flow area
surrounding the poppet in the bore 35 has a cross section~l area equal to or larger than the
inside area ofthe return line. The di~mP~tPr ofthe internal passageway 34 creates a shoulder
at the outlet end ofthe bore 35 that retains the poppet 42 in the bore. The poppet material
has a specific gravity of 1.0 making it neutrally buoyant in water. The valve seat fitting 28
also incllldp~s provisions for ~tt~çhment ofthe water return line on the end opposite the
valve seat 43.
3: Fittings: Pipe nipples 32 and 33 that will connect to standard rç~;~Pnti~l water
piping are threaded into each end of the body 29, with the inlet nipple 32 confi~red to
position and retain the aspirator nozzle 38. A tubing interface for connPctin~ to the water
return line is an integral part of the valve seat fitting 28.
4. Plug: The plug 37 closes the internal passageway 34 to the exterior.
OPFR ~TION OF T~F. ~ NTION
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2176889
The unit establishes a hot water circ~ tion flow any time that a faucet is open and
water is flowing in the building. Referring now to Figure 2, the circulation fiow is caused
by the aspirator 30 located internal to the circul~tion unit 21. The reduced cross section of
the aspirator nozzle 3 8 causes a high velocity in the water passing through the nozzle. The
high velocity water reduces the pressure in the low pressure chamber 39 ofthe aspirator
bore 36. The opening of the internal passageway 34 into the aspirator bore 36 is located in
this rh~mber. Referring to Figures 1 and 2, the low pressure causes water to be drawn
through the return line 24, through the check valve 31, and into the main stream flowing to
the water heater 40. This water is replaced by water from the heater 40 fiowing through the
hot water pipe 26 to the tee 25 at the remote faucet 27, thereby establishing the circul~tion
loop, and providing hot water to the remote faucet.
Reverse flow in the water return line 24 is prevented by the check valve 31 integral
to the circnlfltion unit 21. The neutral buoyancy check valve poppet 42 is wçi~htless in
water, hence it has ç~nti~lly zero friction in the bore 35, resultinE in highly responsive
pelrolll~ ce without stirl~inE Flow through the check valve 31 from the inlet end occurs
as dirr~lel~lial water pressure causes the poppet 42 to move away from the seat 43 allowing
water to flow around the poppet 42 in the cylindrical bore 35. Flow through the check
valve 31 from the outlet end is not possible since the water will force the poppet 42 toward
the inlet end, causing the poppet to bear against the valve seat 43, stopping the flow.
The unit produces a circulation flow rate sllffirient to quickly provide hot water at
the remote faucet with the use of a relatively small return line that makes for simple
in~t~l4gtit)n. The unit will ..,~;nl~in hot water at the remote faucet whenever there is normal
frequency of water use in the bllildinE With the return line tee in~t~lled on the most remote
faucet on any hot water branch, the system will service all faucets on that branch. Tests
conducted with the unit installed in a typical rçcidenti~l water system have revealed no
objectionable reduction in fiow capacity or other undesirable effects. The unit is self
reEul~tinE since aspirator induced circulation ~ow occurs only when water is being used in
the building, thereby conserving heat when hot water is not required.
- It has been conclllded from analyses and operational tests of a prototype aspirator
water circul~tion unit, that it will perform in accordance with the stated objectives. Flow
rates in the return line during typical water use at other water outlets have been measured in
the range of 840 cubic cm/minute. This rate equates to repl~niching the water in the hot
water pipe at a linear rate of 2.5 meters/minute in a pipe with an inside rli~metçr of 1.9 cm
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(.75 inch). This rate will increase by the area ratio when dealing with smaller di~meter
water pipes. The minim~m useful hot water temperature co~ hle with most hollsehold
uses has been determined to be about 32 degrees C. With water use in the building of five
gallons at one hour intervals, water telllpel ~ re in the hot water pipe near the remote
faucet has been measured to stay at or above 32 degrees C. Upon opening the remote
faucet, heater temperature water is quickly available since the water pipe is already heated,
and heater temperature water has progressed part of the ~ t~nce due to the return line flow
resl-lting from other water use in the building. Test results have shown that following
periods of no water use in the b~ ing~ the aspirator water circ~ tion unit will reduce the
time required to bring useful hot water to the remote faucet by approx;lll~tp~ly 80 % from
the as-built water system configuration. The unit is noisele~ except for a minor click as
the check valve closes when the remote water faucet is opened.
The above operational ~ ulssion has identified and defined several advantages
inherent in the present invention as follows:
A. The unit will quickly provide hot water to a remote faucet in response to user
needs.
B. The unit will quietly replenich hot water in the pipe to the remote faucet each
time water is used anywhere in the building.
C. Water will be conserved since there will be no need to run water to waste
while waiting for hot water to reach the remote faucet.
D. Heat will not be wasted when no one is in the building or at night, since theunit responds only to water use in the building.
E. The unit is self re~ ting responding to water use in the b.-il~ling which
in(iicates potential hot water needs.
F. The design concept utilizes a simple, proven approach to draw water through
the circulation loop.
G. The unit is economical to operate, using no electrical power or gas.
H. The inst~ tion is simple and requires minim~l space.
I. The return line is a small tube making for easy in~t~ tis~n
J. Since there is only one moving part, reliability is high with no periodic
m~intPn~nce required.
K. Water temperature never PYf~ee(ls the telllpel~LIlre ofthe water heater, avoiding
a safety issue inherent in high temperature undersink heating units.
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L. Hot water capacity is limited only by the capacity of the building water heater.
- ~u~rARy OF T~V~TION
This invention is a passive, self-re~ tin~ water circulation app~alus, that willcirculate water from the heater, to the remote faucet, through a small return circulation line
and the circulation unit, and back to the heater, for the purpose of keepil~p hot water at
remote faucets when water use in the building signals a potential need for hot water. The
circulation is in~lced by an as~h~lor installed in the water supply line to the building water
heater and cold water outlets. The aspirator operates at any time that water is being used in
the building, and replenishes the hot water in the pipe leading to the remote faucets. The
unit also incl~des a neutral buoyancy check valve to prevent reverse flow in the water return
line. It is primarily int~nded for use in re~identi~l and/or small con~. ne~ cial b~ in~s The
aspirator water circ~ tion unit offers the following unique and novel re~lule~.
A Use of an aspirator in the genel~lion of a circ~ tin~ flow between the water
heater and a remote hot water faucet for the purpose of quickly bringing and ...~;nl~ ;ng
heated water to the remote loc~tiol-
B. A check valve with a neutral buoyancy poppet to e~ in~e gravity effects andresulting friction between the poppet and the wall of the bore.
C. A small return circ~ tion line that can be in~t~lled with the most convenientrouting for each in~t~ tion.
Other embodiments of the invention from that shown and described here are
possible, as well as dirrelel,l arr~nge...en~s ofthe unit in the building water system. The
scope of the invention should not be determined by the configuration shown here, but by the
stated claims herein.
