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One of the last frontiers of creature comforts we continue to pursue is that of on-demand hot water.

Sure you can use a point of use tankless water heater under the sink for one location or invest thousand of dollars in a whole house tankless water heater but these options are out of reach for economic or practical reasons for most people.

But there is a way to get almost immediate hot water from that little old water heater you have chugging away in the basement.

How? By using a device called a demand delivery hot water recirculation pump.

OK, you're going to love this. For between $180 to $500 depending on how fancy a unit you want to buy (some have motion sensors built in, simple ones use just a timer), you can attach this unit to your water heating system and have hot water up to 80% faster (that means within seconds in the summer) than you get today from your standard water heating system.

And besides the comfort of hot water faster, you don't waste our precious resource of water! Did you know that the average household wastes between 11,000 to 16,000 gallons of water a year by letting the water run down the drain until it gets hot enough to use? That is a shocking and disturbing statistic.

Well, read How to Get "Instant" Hot Water with a Standard Water Heater and see how easy it is to enjoy hot water faster, while saving money and a precious resource!


June 16, 2008 at 3:36 am
(1) jane says:

nice post, thank you for sharing

June 16, 2008 at 12:04 pm
(2) Nanonuke says:

Excellent article.I was just looking for something like this to prevent water wastage. This is going in my Staying greeen blog :-)

June 19, 2008 at 9:54 pm
(3) Dave says:

Thanks, what great way to save water.
I’m not very happy with my water situation since it’s seems to take such long time for at least some warm water to come out of the shower.

A couple weeks back, I heard a message on the radio saying in 3 minutes time of running the water in the shower is roughly 18 gallons of water. Knowing this just drives me crazy.

June 20, 2008 at 11:27 pm
(4) homerepair says:

That’s right Dave, if you have an older style pre-1992 shower head, it can use 6 to 8 Gallons per minute, so waiting 3 minutes for the shower to warm up can waste 18-24 gallons of water.

June 24, 2008 at 9:15 am
(5) Todd J says:

Our home had a real problem with this issue so our builder (Ryan Homes) installed one of these units a few years back gratis. It really works, but the downside is that your cold water ends up running pretty HOT! A real negative when you’re trying to make Kool-Aid or soothe a burn! If you need cold water you end up wasting water waiting for it to cool down.

If you’re building a house, have the plumber run a separate return line to remove this problem.

June 26, 2008 at 9:32 pm
(6) Tommy says:

Good article, however, would like to have seen more diagrams and a discussion about the downsides of retrofitting a recirculating pump versus its use in new construction.

In my new house, the hot water circulates through a dedicated closed loop built into the original plumbing. This uses some energy due to heat radiated out of the pipes, but always returns unused hot water back to the water heater and does not touch cold water.

The article, however, describes a retrofit using the cold water lines as a return path for the hot water instead of using a dedicated return path. It seems to me that in this application, the recirculating pump–when active–would also heat and keep the water in the cold water supply lines near the valve shutoff temperature (95-98 degrees). In addition to giving instant “hot” water at your hot taps, you’re also paying to heat instant “warm” water at any cold taps between the valve and water heater.

This seems potentially like a big waste of energy, heating water in the “cold” supply lines that you don’t need (or want) to be heated at all. Some of that warmed water would literally go down the toilet or, even worse, get fed to an icemaker that uses even more energy to cool down the water you just heated up. Also, instead leaving your hot water tap on waiting for it to warm up, you’d occassionally have to leave the cold tap on waiting it to cool down.

With an on-demand electronic pump, one could activate it only when hot water was truly needed. A timed recirculating pump at the water heater, however, seems like a waste of energy without a dedicated return line.

July 4, 2008 at 8:28 pm
(7) ron metropolit says:

It may be a waste of energy heating the cold water but in a totally finished house its next to impossible to instal a dedicated return line. It sounds like a great idea to me. I am in the natural gas industry and customers would often complain of long wait times for hot water.This type of product would satisfy them.

August 1, 2008 at 10:24 am
(8) Da Plumber says:

hot water circulating piping is NOT nearly impossible in a finished home. you might have to make a few small openings in the drywall to connect piping, but thats cheap to fix. you’ll need only the expertise of an experienced REPAIR plumber.

November 29, 2008 at 10:01 am
(9) Danny says:

if I have a tankless waterheater already and need hot water on the other end of the house, how can I do this

December 21, 2008 at 5:17 pm
(10) Prygaard says:

A recirculation pump with a dedicated return line and a timer has two problems:

1) Most of the time the pump is running it is not needed.

2) when Hot water is needed, the pump is often not running.

I solved the problem with a unique “on-demand” control that turns on the pump when the hot water anywhere in the house is turned on.

1) On the cold water IN on the Hot Water tank, a flow switch that turns on when it detects flow. (Note: The flow sensor can *not* be anywhere in the circulation loop)

2) A Delay-Off timer turns on the pump immediately when the Flow Switch turns off, but does not turn off the pump for a while after the flow switch is turned off. (The delay time needs to be adjusted for the characteristics of the particular installation. Typical times range from 30-90 seconds)

3) An aquastat is used to turn off the pump when the farthest faucet in the loop reaches temp.

When the hot water is turned on, the pump comes on and hot water arrives fairly quickly (but not instantly). The innovation is this: Turn the hot water on for a second and then turn it back off…and the pump keeps going for a while. Then just wait for a little bit and turn the Hot water back on…it is hot and ready to use. However, after the water is turned off, the pump will run for the delay time and then stops till the next time there is demand.

Parts I used:
Flow Switch: Gems 26605 (I got it cheap on ebay). (http://www.gemssensors.com/ApplicationSearchResults.asp?nQuestionID=36 ) Others are available, but be sure to get one that has a fairly low trip point on the flow. (.75 1 GPM)

Delay off Timer: MX046 timer kit. (15 second to 6 min delay)
(http://www.bakatronics.com/shop/item.aspx?itemid=466) It is inexpensive but you must build it into a case. There are other delay-off timers and relays available but this seems to be the cheapest option.

Aquastat: Grundfos 1/2 Clip-on Part #: 59 56 56 (http://www.nextag.co.uk/GRUNDFOS-1-2-Clip-524919497/prices-html?nxtg=a1b20a280504-452EC488A496B3D0)

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