Hot Water Recirculating Pump

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True or False?
A hot water recirculating pump won't decrease the amount of time it takes to get hot water to a fixture, it will only eliminate the waste caused by the water running down the drain.
True, right?
(Another Ask This Old House inspired question)
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On 2/11/2012 1:39 PM, DerbyDad03 wrote:

unless it: a. runs all the time or b. is a passive gravity system
the whole idea of the passive system which will work in any house with a water heater below the level the fixtures are on, is INSTANT hot water. We had it introduced to us in 1970 when my parents built on to their house. It worked (and still works) great!
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Steve Barker
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But these waste a lot of heat because they are continuously circulating. We have a second home in Fl and the water heater is at one end of the house and 3 bathrooms at the other. it can be a pretty good wait for the hot water to come up so I installed one that you hit a switch to call up the hot water. I mounted the switch by the the light switch in the bedroom figuring this would give the pump a bit of a head start before you made it to the bathroom.
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On 2/12/2012 3:42 PM, JIMMIE wrote:

the 'waste' is minimal during cooling season. and zero during heating season. It's about instant hot water, not about energy. I could really give a big rats ass if my gas bill goes up by 85 cents a month to have instant hot. Thanks for your input. The pump setups don't save anything.
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Steve Barker
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How?
Here's the situation shown on Ask This Old House:
The homeowner had a tankless water heater installed. It was installed at the opposite end of the house from the second floor bathroom and the plumber used 3/4" pipe from the unit to the bathroom. The homeowner used a stop watch to show that it took a full minute to drain all of the cold water out of the pipe before there was hot water at the fixture.
A recirculating pump with a push-button control (and a remote for a second bathroom) was installed under the bathroom sink.
How would a recirculating pump speed up the emptying of the pipes? It still has to pull all of the cold water out of the pipes before hot water could reach the faucet. Does it move the water at a rate much faster than the normal water pressure in the house can move it? If so, wouldn't that faster flow rate be too fast for the tankless water heater to heat it up?
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On 2/11/2012 3:10 PM, DerbyDad03 wrote:

I don't know that one would work with a tankless heater because the tankless needs flow for the heat to come on. The type of loop I generally see is connected to a standard hot water tank. It has a bronze circulator pump controlled by an aquastat. In circulating the hot water off of the top of the tank, it keeps the entire loop hot
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Agree with RBM. If it's connected to a button, then I doubt there is going to be a huge difference in the time it takes for the hot water to arrive. The pump could move the water a bit faster than just running the tap, but it's still going to take time to get there. If it has a timer and temp sensor, then it can have hot water there during the hours you set it for with zero wait. Always thought this would be a good application for a motion sensor. As soon as you walk in the bathroom it gets the pump going.
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when watching that episode it took approximately 60 seconds without the pump and what seemed to me to be much, much less time after she pushed the button
of course if the recirculating pump pumps more gpms than the tankless produces then it doesn't make sense
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Modern faucets are infected with Energy Star disease. This means they only pass water at 2.5gpm, or if they have the particularly virulent Water Sense disease, 1.75gpm.
A recirculating pump can move much more than that.
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Wow, sounds like you're talking about over age 50 prostates. "Only delivers zzz flow rate, and empties in xxx minutes while standing over the bowl."
I'm soon to be needing one of them recirculating pumps. Cut down on my prostate time.
Christopher A. Young Learn more about Jesus www.lds.org .
Modern faucets are infected with Energy Star disease. This means they only pass water at 2.5gpm, or if they have the particularly virulent Water Sense disease, 1.75gpm.
A recirculating pump can move much more than that.
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On Sat, 11 Feb 2012 12:10:41 -0800 (PST), DerbyDad03
<snip>

I think the idea is that you press the button when you first enter the bathroom. By the time you have... umm.... taken care of business, or are ready to get in the shower, the pump has done it's job and you have hot water.
You could also use a timer to run the pump for your normal shower time, with the button as a secondary trigger. Some of the recirc pumps sense the water temp and stop pumping when the hot water arrives, so it wouldn't run continuously during the timed perior.
Could also tie to the light switch or even a motion sensor.
As far as flow rate, you could easily double the rate of a typical shower head and not be an issue with a tankless, as they are always sized to handle multiple fixtures at the same time. That would cut the time in half.
Paul F.
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Iit's just as appropriate to tankless as to storage type heaters. It's just an issue of where the heater is located. If you have a storage type at the far end of the house from a bathroom, it's going to take a long time for hot water to get there. Replace it with a tankless and you have exactly the same problem.
How can one guy be wrong on so many things?
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wrote:

Practice?
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harry wrote:

You scurrilous pile of shit! To you, everything outside your four walls is devoid of merit.
I'm going to Manchester on October 15th. I will find you and make you curse the day you were born, asshole! You will rue the day you embraced anti-Semitism, anti-Americanism, and all of the rest of the things you dislike.
But "dislike" on your part is pretty mild when compared to the hatred on mine. If I were you, I'd donate a unit of blood to the Red Cross today so you'll be covered for transfusions later in the year.
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True - but as in most things in life, it's a trade off. A recirculating pump keeps the water in the hot water line hot so that when you open a faucet on that line you get hot water immediately and don't have to let the faucet run for a while.
You can also do things to minimize the energy use. Ours is on a timer so that hot water is available immediately in the morning and evening. The rest of teh day you have to run the tap for a period of time. You can also wire push button timers at each location.
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Many such systems use a sensor or a timer to keep the entire loop of pipe hot (pipe is of course insulated). I think my approach will be either a button or maybe a motion detector.
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DerbyDad03 wrote:

Timers, buttons, pumps, valves we have come a long ways from the old days when water was heated in buckets on the stove top for the once a week bath. I solved my wait for faster hot water in the kitchen by running one line under the floor to the kitchen sink straight as possible from the HWT. Looks like its about 25 feet of pipe run now, 1/2 inch CPVC. instead of maybe 40 feet of old steel pipe that had lots of deposit build up. I just timed it, 15-20 seconds for the hot water to show up another 3 seconds for it to be as hot as it's gonna be. Works for me.
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A friend of mine has a setup exactly like the one installed in Ask TOH but with some extras. It is important to understand that it is NOT a recirculationg pump one would normally think of. It does recirculate the wayer, but NOT directly back to the water heater, but vack into the plumbing system of the house. A few years back IIRC onASkTOH, a recirculating pump was installed for a tank type hot water heater. That system did send water back to the heater's tank. (Someone correct me on this if I am wrong)
My friend's contractor gave him this expplanation on using the system:
The button (and remote button inthe next bathroom) is there for you to push IN ANTICIPATION of hot water. It causes water to flow thru the water heater, thus causing the heat exchanger to begin heating water and then moving toward the point of demand. The cold water it is displacing is sent back into the house's plumbing system and not down the drain. My friend's pump is set to shut off when the pump input water temp is at the desired temperature. He also had an indicator light (not sure where) put in to indicate pump activity. (He had a failure of something in the heater such that the heat never came on and the pump ran on and on, but since it was hidden behind towels and such, he never heard it running).
The system does save money, but mostly on gas to heat the water, and less on water coming into the house and then down the drain.
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Which is one of the big problems with them. You wind up with tepid water from the water heater in the cold water lines. Not a problem if it's feeding a shower, but if it's the cold water line for the kitchen that it winds up in, then when you draw what you think is fresh water you could be in for a surprise. Where the water winds up depends on the path the water takes back and what else is on that path.
A few years back IIRC

Don't know about TOH, but it's certainly been done. During construction it would be very easy to do.

I guess you save some gas from the fact that the water that's been sitting in the line and is at say 65F goes back to the water heater instead of using say 50F incoming water. But in the grand scheme of things, I don't think it amounts to much. And of course if you use a timer or keep it available 24/7, then you wind up using more energy.
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My understanding is that a properly installed circulator both:
1) Reduces time to get hot water from a faucet 2) [therefore.....] reduces waste
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Christopher A. Young
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