This is my first visit to this group, so the question may be
I am thinking about installing a return pipe on my hot water
feed to the kitchen to reduce the amount of cold water that
is wasted before the hot water has reached the sink.
Where is the best place to make the connection close to the
hot water tank? It takes nearly four litres of cold water to
run through the pipes before the hot water arrives. I have
lots of pipe and connections left over from different
projects and I might as well use them for this. My ceiling
is easy to access. My problem is knowing where to connect
near the tank.
I have also read that some people have installed a "U" near
the tank to reduce the loss of heat when hot water is not
being drawn for use. Anyone have any details about this idea?
Many thanks for your ideas.
Remember, you are going to have to have an external pump
to do this because the pressure in the cold water line is the
same as the pressure in the hot water line.
To have instant hot water, the pump must operate continuously.
This is a valid technical solution to your problem, but a costly one.
I would suggest that you put a flash hot water heater at the
point of use. That way you wouldn't need to use energy until
you are ready to use water.
On the other hand, 4 litres of water doesn't cost much. It is
about the same as flushing a toilet.
In my house, I have installed a smaller hot water heater
in series with the hot water line at the point of use. It doesn't
work nearly as well as a flash heater, or the recirculating
pump that you propose, but it works well enough....
Just some suggestions...
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Maybe you could use a chilipepper...
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Interesting little machine, but not economical for me. I
don't pay for the volume of water that I use - flat annual
fee and electricity to heat the water is about $0.07 per kw
hour (cdn) so I would have to llive a long while to pay for
the little hot one.
Thanks for the link. It never hurts to know what is on the
Without going into the invoice pile, I recall that it is
$120 or $180 per year for a single dwelling. Enough for us
because we don't waste/use a lot of water, but for people
who want everything to be green ans clean (cars, driveways),
it is not enough.
That connection doesn't necessarily need to be hooked near the hot water
tank. A short run straight to the cold feed for the kitchen and a pump in
that run would work and could potentially be much easier to install. The
pump would move the 'stale' water from the hot water line through the cold
water line back to the heater. I believe there are kits with thermostat
controlled pumps even for this kind of hookup. Then the pump doesn't have to
run all the time.
You can create a thermosyphon by bringing a return back from the hot
water line near the faucet and connecting it to the bottom of the water
heater through a "swing check valve". That valve will prevent cold water
from moving towards the faucet.
But keep in mind that unless you insulate the piping you'll be
constantly leaking quite a bit of thermal energy from the system which
will have to be replaced by using additional electric or gas.
You can use a amall circulating pump controlled by a timer or proximity
switch and also a temperature sensor so that it only runs when the water
near the faucet is below a preset temperature and when you expect to be
in the kitchen (timer) or when you are actually in it and moving around
(proximity sensor). Again, insulation of the piping will avoid wasting
too much energy.
There are some systems which use a small pump under the sink controlled
by a similar temperature sensor and timer or proximity switch which push
the water from the hot water line back down the cold water line. These
do work, but if you want to draw a glass of cold water, you have to
waste water while you drain off the warm water in the cold water pipe.
Again, insulation of at least the hot water pipe will help save energy.
All in all, I'd suggest you do the math and try and calculate how much
the water you are wasting will actually cost, and compare that with the
added energy you use and the amortization and maintenance costs of
whatever "immediate hot water" recirculating system you decide to use.
Chances are a "local" point of use instant electric water heater will
end up costing you less in the long run, and won't "waste" any water.
(W1BSV + Brass Rat '57 EE)
"Truth exists; only falsehood has to be invented."
I really have to wonder if any of these solutions would save any money,
even in the long term. Water is typically very very cheap. Electricity
& gas not so cheap. Buying instant electric heaters and what not are
even less cheap. And paying for repairs, even if it is just one leak in
a lifetime, could put you forever in the red on this project.
I have seen claims that the average family wastes 27 gal of water a day
waiting for hot water. I can't even fathom that. We waste, maybe, 2 gal
tops a day. E.g., I wait about 10 seconds before getting in the shower.
When washing dishes (2-3 times a day), I rarely ever wait at all, as
the water isn't that cold to begin with.
On the environmental side, pouring a gallon of water down the drain
once or twice a day might not be such a big deal when compared with
manufacturing a hot water heater, or drilling for gas, or burning coal
for electricity, etc. In many cases, the water will just go right to a
septic or greywater system anyway.
Why not just go get some cheap pipe insulation, put it on your hot
water lines, and see how it works? This is doable for probably less
than $10, and 15 minutes of effort.
Good comments. I often try to calculate the total "cost" for
my actions from the environmental side. I can not justify
buying a new or newer car to save a small amount of gas. I
just drive a little less. As for this idea, it is not
critical - the little water that I "waste" dilutes some of
the real waste water that is in the system so it does serve
The hot water line is already insulated. Whatever heat
escapes ends up contributing to the heating of the house so
the energy is not lost completely.
thanks for the comments.
if you have city sewers, the water-treatment-plant operators would
tell you a different story. The more water becoming septic, the higher
everyone's taxes will be.
In other fora is discussed the fact that, it not only is cost-effective
to keep water away from human excrement, but it's actually
cost-effective to keep urine separated from #2, right from the git-go.
Do you meat a re-curculting line that keeps the water in the line hot all
There will be a net lo$$ in the end. Having instant hot water is nice, but
the little bit that goes down the drain is cheaper than keeping the pipe hot
all the time.
If you are somehow using this only when the water is turned on, there may be
On mine, I had a nipple put between the tank and the drain, and plumbed
the return line into that. Yes, it will mean a little extra work when
the heater has to be replaced. I save a lot of water because the supply
line across the basement is 3/4 inch, and around here the water rates
have gone up far more that gas or electricity. I insulated the supply
line and left the return uninsulated, and it works well without a pump,
but I have a lot of vertical line to the upstairs bathroom where the
crossover is, and I'm sure that helps.
Its true that there is some heat loss, but where I live we have far more
heating than cooling days, so I just consider it a radiator. Installing
a check valve will prevent any back flow.
Don't recall all the details but a house I used to own had a re-circulating
system (to the baths, aprox 40 feet) that worked great but used no pump. If
I remember correctly it used a 3/4 in pipe up through the attic as a feed
and a 1/2 in pipe as a return under the house. The 1/2 return connected to
bottom of tank at the drain valve. I assume the 1/2 line was used as a
The house was built in 1952 and the builder installed this setup when it was
built. We lived there aprox 35 years and never had any problems with it, had
instant hot water at the tub and bath room sinks when the valve was opened.
I would not have liked it, had we had small children. RM~
PS, It was a natural gas fired water tank.
If you're only recirculating the kitchen line, I doubt you'll save enough
water to matter.
I installed a recirculating system in our house, for convenience, not
energy savings. With long 3/4" supply lines and low flow shower heads, we
were waiting well over a minute each morning for hot water to reach the far
shower. While it did waste a lot of water, it simply wasn't convenient.
After installing the recirculating system, we have hot water in about 5
seconds (nearly instantaneous on the full flow tub faucet).
Usually, the return line is plumbed into the drain valve at the bottom of
the hot water tank, with a tee for the drain so you can still empty the
tank. But, my tank sits in a small alcove down in a deep drip pan. So, I
couldn't make a connection there. Instead, I put a tee on the cold water
inlet, and tied my recirculation line in there. It requires a check valve
in the return line, valves to turn off and bleed air out of the return
line, and of course a pump (though there are methods of making thermosyphon
recirculators). My recirculation line is 1/2" and I used a Grundfos pump
with a built-in timer. It runs a few hours in the morning, and a few hours
in the evening to cover most of our likely showering times.
Other than the regular insulation in our floor, I did not insulate our hot
water lines. When the pump is running, it's easy to tell there is heat loss
from the hot water and recirculation lines. The floors above the pipe runs
are warm, like radiant heat. Feels nice on cold mornings. :) But, it is an
energy loss. It also warms the cold water lines a bit that run close to the
hot water lines. So, we have to run the cold water a few seconds
when we want really cold water. Compared to the rest of our energy use I
haven't noticed any major change in our electric bill (we're all electric
We're on a private well, so I have to think the energy loss from the
recirculation system is offset by not having to run our well pump as often.
Heat rises, so if your tank is lower than your fixtures, it might be a
smart idea. In my case, the hot water tank sits above all the plumbing runs
in the crawlspace. So, it makes a "U" naturally by coming up out of the top
of the tank, and heading down to the crawlspace below.
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