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Question DetailsAsked on 3/12/2015

Best water re-circulation pump for water heater?

Planning a new house thinking of putting the water heater in the garage instead of the attic but it will be further from the bedrooms. Are these water re-circulation pumps a good option to get fast hot water? What brand would you recommend?

Do you typically do push button, a timer or a motion sensor? Can you use a single pump for multiple bathrooms or would I need a pump per bathroom?


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5 Answers


You seem a touch confused on what a hot water system recirculation pump does. Instead of the hot water pipes being dead-ended from the water heater so the water cools off in them between uses, the circulating system puts in a return loop through all usage points desired and a single pump so the hot water is constantly recirculating through the water heater. Pump is usually put near the water heater so maintenance is easy and its slight noise is in the utility area. Makes for almost instantaneous hot water because only the water in the pipes and tubing leading from the circulating loop to the usage point cools off - a second of so of flow when you turnn it on.

Does consume small amount of electricity constantly (like a constant-on light bulb), andif any of the piping passes through unheated area like crawlspace and is not well insulated then does act as a hot water heater for that area, wasting some energy. Also, in air conditioning country, the waste heat radiated from the piping results in a slightly higher air conditioning cost, so insulation of the loop piping can be important in that case too.

Circulating pumps - in order of my personal preference/confidence, Taco, Grundfos, Watts, Bell & Gossett.

When you talked about a push button, timer, or motion sensor - that is a way of automatically turning on a hot (or cold) water faucet with a powered faucet - totally separate from the hot water system itself, and can be put on any hot water source.

Your other alternative is a point-of-use hot water heating unit, that heats the water electrically as you use it - commonly done either for entire house using a tankless heater as a replacement for a tank type water heater, or only for kitchen sink at times. Google for that subject if interested - but costly, and in my opinion the technology is not up to the point of them being long-lived or economic enough for general use in residences yet.

Here is another prior question with response FYI also -

Answered 5 years ago by LCD


Replying back to my question as a follow up to the answer I just received:

Very much appreciate the description of the loop that is helpful in better understanding how it works.

When I mentioned "push button", "timer" or "motion sensor" I had heard it mentioned that you could use those as mechanisms to trigger the pump so instead of having it always circulating water you could reduce energy use and push a button right before taking a shower to have it circulate the water around the loop. Instead of running it all the time. Is that ever actually done?

Thanks appreciate the advice!

Answered 5 years ago by Guest_9169994


On the switched-pump issue:

These systems are not that common - sure you could do that, but would only turn pump on for that specific use, not say for instance to get hot water quickly at washing machine, dishwasher, sink, another bathroom, etc. unless you ran a circuit with multiple switches to turn it on, which is just that many more things to potentially fail.

It is also possible to put a pressure-activated switch on it, like a well pump uses, so it turns on when the pressure in the pipe drops due to hot water use somewhere - that is probably the simplest approach to your questionand it works with demand at any point then, though might end up turning on at times when high-volume cold water is used too - like tub or garden hose or washing machine, so might need an adjustable setting pressure switch so you can "fine tune out" that sort of unwanted operation.

Also, if you did that, you would have to install the pump in the return circulation line heading back to the water heater, so it would not inhibit straight-through flow in the "feed" pipe when hot water was demanded at other locations. Also, you would have to be sure to buy a model designed for intermittent running rather than continuous, as many of the continuous run ones use centrifugal-action water lubricated bushings that commonly leak when the unit is turned off.

To be perfectly honest, I don't see much benefit in a switch versus just leaving it running full time - typically 1/25 to 1/10 HP pump, so about 30-75 watts use (though granted that is $20-100/year depending on your electric rates and pump size) - about same as leaving a light bulb on year-around. Of course, I actually don't see the benefit of the circulating pump system anyway in most cases - perhaps in very long-run ranch or hacienda houses or where the hot water pipes run through crawlspace or unheated basement and are not insulated, and perhaps where water is very pricey so saving water by not running it to get it hot, but I see no problem in normal cases with running the water direct to the drain for 2-4 seconds till the water coming out is warm before turning on the spray head.

One thing on the circulating loop system which I think you caught but in case you did not - it does require putting in a second hot water pipe looping through all usage points and back to the water heater, so additional cost putting that in plus you have added close to 50% more pressurized pipe to leak in the future, if that concerns you.

Installed cost - typically around or above $1000 unless your water system is built pretty central to the center of the house, in which case you might get it for under that - but does involve cutting into pipes a number of places to put in the return loop - plus of course drywall/plaster repair and painting if access through finished surfaces is required, so can get up into the $2000 totall cost range in a spread-out or 3-story water service situation. Obviously, on the cheaper end if one story with easy crawlspace or basement open joist access to the pipes.

Answered 5 years ago by LCD


I believe LCD has answered the question, but I'd like to add a testimonial. I am in my second home with a recirculating hot water system and I very much like it. City water here is very expensive so I try to minimize waste water. My older (1906) home has a crawl space through which the major plumbing lines go and the hot water tank is in a small basement in the center of the larger crawl space. Here in North Carolina in winter, the cold water is really cold, and to be able to mix with hot in a matter of seconds throughout the house is amazing, and worth in investment and running costs to me. For summer use, I set the pump to be on only during morning and evening for hand-washing. Some of the things suggested to me by contractors and our plumbers:

- Avoid the tricky plumbing and circuitry required for the push-button, crossover, and pressure-drop control systems. These are more expensive to install, may require you to do things other than just turning on the faucet, and are not friendly to repair. Complexity can work and work well, but requires constant care and feeding.

- Grundfos pumps are widely available, quiet, reliable, and have worked well for me in two homes. The pump has an LED light on its side indicating it is running, otherwise I would not even know.

- The pump model has a built-in mechanical timer that can be set to be "on", "off", or on a timed cycle on and off whenever you wish. During winter I just leave it "on" all the time, in summer I have it on for a couple hours in the morning and evening.

- I have lots of 1/4-turn valves to control flow through the recirculating and hot water lines. This makes it easier to repair any leaks, service the pump, etc. Put these near the hot water tank.

- Use lots of pipe insulation everywhere you can, but especially in unconditioned crawl spaces. Even though the pipe may be Pex or other plastic, it still loses lots of heat in cold weather. Insulate both the hot water line and the recirculating line, maybe even the cold line if you experience freezing temperatures where your pipes are.

- You will want a 110v grounded outlet close to the pump so you do not need an extension cord. The pump draws little current when running so it does not have to be a dedicated circuit but local codes MAY require a GFCI or even an arc-fault breaker.

I have not noticed any incremental electric expenses though I'm sure there are some, and I've not noticed water savings, though I'm sure there are those too. What I HAVE noticed is nice warm water in winter within a few seconds of turning the faucet on, and that is just wonderful. I'd like to think this helps dishwashers and clothes washers as well since today's models use so little water you would never get warm or hot water from just the supply line.

Answered 5 years ago by SalisburySam


A couple of good catches by Salisbury Sam - well done, Sam.

I had totally spaced on the expensive water thing, because it has been several decades since I lived where water was metered and charged by usage. However, you would likely only be using probably a gallon or two more a day letting it run to get hot before each use, so at common expensive area water rates of about $10/ccf that is only about $10/year for the approximately 100 cf/yr that would consume. That compares to around $40-50/year (assuming $0.18/KWhr) for the electricity to run a 1/25 HP circulating pump continuously - obviously less if on timer, BUT you would have to be sure to have a flow-through or bypass type pump which allows relatively free water flow when it is off. So, in almost all cases, just running the water till it runs hot would be cheaper unless you are talking a VERY long run to the far end of a ranch house, for instance. (About 50 LF of 3/4" pipe = 1 gallon of water).

To assure full flow to showers and tubs, you would have to either make sure the pump is on or have it rigged as a parallel bypass pump - in parallel with a full size line that the water can flow through when the pump is off, with backflow preventer so when the pump is on it does not just recirculate from the pump through the bypass and back to the pump. As you can see, every complexity you add in, the more there is to fail.

I like Sam's time-of-day philosophy - you could just put in a plug-in in-line time of day timer like is used for lamps when you are away (with adequate wattage capacity for pump starting amperage, of course) - which if it fails could just be unplugged and taken out of the circuit to let the pump run continuously until a new timer is obtained. An advantage to the pump being rigged with a plug and cord rather than hard-wired, though some jurisdictions REQUIRE it be hard-wired.

If going with an intermittent-run pump, be sure to get one that is rated for that - many circulating pumps with water-lubricated bearings leak when they are off - in my experience, Grundfos are especially bad at this, and Taco is very good. For that application, be sure to get a two-part pump unit - where the pump is bolted to a separate electric motor, and there is a drain hole from the pump so if the bearing seal leaks it drips out instead of shorting out the motor. The single-unit designs short out the motor if the water lubricated pump bearing fails. Also, make sure it is mounted where a leak from it (because seals do go out at times) would not be catastrophic - NOT near electrical panel, and NOT over heat pump or furnace/boiler which could short out from water spray, because when they fail it is usually be a fine mist or spray which reaches out 5 or more feet.

As I read the electrical and plumbing codes, such circulating pumps HAVE to be GFCI protected, because a failure could shock anyone through the water system.

BTW - when Sam was talking about the 1/4 turn valves, he was talking about ball valves - the "valve" mechanism is a ball with a full-diameter hole drilled through it, so when aligned with the flow has very little friction, and then when turned 90 degrees to the flow is totally off. Good for emergency shutoff and isolation valves for systems that might need changing out frequently or which you would not want to drain out for maintenance - especially just before air vents on boilers for instance, so you can change the item out without draining the whole system.

A recommendation on ANY pump you put in - tell them you want Buna-N or Butyl (the softish black) gaskets or O rings (as applicable) where it flanges into the pipe, NOT the gray or red rubber ones - they get brittle and rock hard quite fast in hot water service, so the pump noise is then transmitted to the piping as an audible hum, Also they start leaking a lot faster because they crack and do not stay flexible and press against the flanges, so you get weepage after a year of two and can easily break the flanges trying to tighten them down enough to stop leaking. The higher-grade gaskets typically cost only a dollar or two each, so not a big thing to use them.

Answered 5 years ago by LCD

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