Saving Water in California with a Hot Water Recirculation Pump

pump you'll hear described laterYou MIGHT have heard that California is having a wee bit of a drought while many other places in the world are suffering with record rainfall. Until we figure out how to level things out across the globe (which will end up causing some other natural disasters I’m sure), we in California are looking for ways to save water. At my house one of the things that drives me bonkers is how long it takes for the water in our bathroom and kitchen to get hot. I hate seeing all that precious water literally go down the drain every day while waiting for hot water!

My brother Grant is really smart about stuff like this, and very environmentally conscious so I called him and told him to find me an easy, inexpensive solution to this that did NOT include me carrying buckets of water down the stairs to wash my clothes. While he’d heard about ways to circulate water around your entire plumbing system in your house, they involved replumbing much of the house so it didn’t meet my requirements of easy and cheap.

Grant and me at Christmas with him wearing his "You'll shoot your eye out" shirt. He had his eye shot out when he was 4 years old. Weird sense of humor.An hour later he called me back to tell me he thought he’d found the solution. He found these things called Hot Water Recirculation Pumps. It sounds like the same thing I just described but it’s a very clever solution that does NOT require replumbing the house. There are two parts to the solution: there’s the pump itself that gets connected to the hot water output of your water heater, and a small passive valve that you put under the farthest sink from the water heater. The valve is the clever bit.

The valve goes between the hot and cold lines of your sink. It has a thermostat in it that measures the temperature of the water on the hot side. Let’s say you set the preferred starting temperature at 90°F. When the temperature goes below 90, the valve opens up, allowing hot water to be pushed by the pump from the hot side to the cold side. This is how it’s different from a full circulation system, which requires a loop on the hot water line. The pump will now push hot water towards your sink through the valve until the temperature is back up to 90 degrees, at which point the valve will close itself.

There’s one downside to this and it’s that your cold water is sort of lukewarm now, but in our house we don’t ask for cold water nearly as often as we want hot water, and cold comes from the source really quickly anyway.

The good news is that we had two engineers involved in this project, so you know we’re going to get some good metrics, right? How else would you know if this solution really did the trick? The pump Steve bought is the Watts 500800 Premier Hot Water Recirculation Pump for $200 on Amazon. The good news for us is we were buying a new water heater anyway, and David from Stephen’s Plumbing agreed to install the pump for free. One caveat is that the pump requires power, so if you don’t have power in the water heater closet you’ll need to make that happen too.

Steve installed the valve under our sink by himself. I don’t mean to diminish Steve’s plumbing skills at all but this must have been an easy job. It only took him about 20 minutes and he made ZERO trips to the hardware store. Made me doubt he did it right!

craftsman_ir_gunWe measured the time it took the water in the sink to go from its ambient temperature to 100F before and after the pump and valve were installed, and we did the same test on the shower. But of course we had to have a cool gadget to measure the temperature so Steve used his handy dandy Craftsman Infrared Thermometer ($40 on Amazon). This is so much fun to play with – you shoot a laser at the water and the display gives you an instantaneous digital readout of the water temperature.

Let’s talk metrics now.

  • The sink started at 72F before we had the pump/valve installed, but started at 92F after the pump/valve installation so we had nice warm water to start with.
  • Before the pump it took 54 seconds to heat up to 100F, and only 22 seconds afterwards! That’s a 32 second or 60% drop in wasted water!
  • The shower was almost as impressive. It went from 1 min 8 seconds before hand to only 36 seconds afterwards. That’s again a 32 second drop or 47% drop in wasted water.

We can absolutely call this a HUGE success from an annoyance perspective, I can’t be waiting around that extra 32 seconds – I don’t have that kind of time! But how much water are we saving? That required us to measure how much water was wasted in those 32 seconds before the pump and how often do we heat the water up in a normal week. I’m afraid we didn’t have a sophisticated laser method to measure the flow, instead we used a bucket and the stopwatch on my Apple Watch.

We measured how long it took to fill a gallon in the bucket from the shower, and how long for a quart in the sink. Then we approximated how often we do this in the bathroom and the kitchen sink where it used to be equally bad. Oh, I almost forgot to mention that fixing the upstairs (farthest) sink from the water heater did also fix the kitchen sink. If you find another sink in your house that isn’t heating up quickly enough, you only need to buy and install another valve for that sink.

Are you ready for the bottom line? For the cost of a $200 pump and valve combo plus the cost of installation (probably less than a hundred dollars), we will save 2863 gallons of water a year! You might be worried that we’re constantly running a pump and now wasting electricity, but the pump comes with a timer that lets you specify what times you want instant gratification. I would call this a success on every front, and I have to give credit to my brother Grant for it, which kills me.

4 thoughts on “Saving Water in California with a Hot Water Recirculation Pump

  1. Bob Goodrich - June 5, 2015

    Only an engineer would measure with a bucket and stopwatch (giggle)! I know because I’ve used a stopwatch to measure boiling time on a flat surface stove. My only bitch was that I didn’t have a coiled stove beside it to compare. HA! I have a similar problem with my hot water on the other side of the cabin. My solution (which I didn’t use because of pressure issues) was to put in instant hot water heaters. I believe they can be either gas or electric. Lost interest when I found they might not work on a gravity flow system like I have. Don’t really have an idea which one would be most cost effective.

  2. Mario Obejas - June 8, 2015

    I installed a pump from gothotwater.com back in 2007. Similar idea but two differences:
    1. New houses, like ours, have a recirculation line. So the hot water flows from the heater around the house and back to the heater. The pump auto shuts off when it detects a rise in temp in the return line.
    2. The pump is wirelessly activated via doorbell buttons we installed in the bathrooms and kitchen. Press the button, start undressing, and hot water is ready by the time you are ready to enter the shower.

  3. Jamie - June 27, 2015

    I have a very similar pump setup, which we got as part of a kitchen remodel.

    I have no doubt you are saving water, but the more significant question may be if you are saving/wasting energy. In my setup, the (uninsulated) hot and cold water pipes are buried in the ground, so I’m pretty sure that while the pump is running, I am trying to heat the dirt under my house with my hot water heater. Not energy efficient, but I love the convenience. If you have solar hot water, maybe that’s not a factor.

    One issue you may see is that the recirculation valve will fail after a couple of years. That little plastic do-dad is $40! But, it is easy to install. Mine is under the bathroom sink. The water in the hot and cold taps are always the same temperature. It’s so far from the water heater, that before the pump was installed, or if it is turned off, they are both cold. (I never leave the sink tap on long enough for it to get hot.) When the valve is working properly and the pump is on, the hot and cold taps both produce warm water. After the valve failed, both taps produced hot water. So, no matter what, they are both the same temperature.

    I got one of those infrared thermometer gadgets ($36 at Harbor Freight). I got it for some issues with the temperature of my gas grill. Every geek should have one.

  4. Steve Sheridan - June 28, 2015

    Mario, that no doubt is the best solution if the hot water recirculation lines are installed when the house is built, but we didn’t have that option. It is too cost prohibitive to plumb those lines after the house is built. This post if targeted to people who don’t already have hot water recirculation lines installed.

    Jamie, where we are located the recirculation pump turned out to be the right answer. This is because we live in an area that never gets very cold and our hot water lines don’t run through the slab but instead through our walls and ceilings. So we don’t lose too much heat from the hot water lines, although I’m sure there is some loss. Also our hot water is heated using natural gas which is a very cheap fuel. For us, the convenience of instant hot water and the savings in water outweigh the slight loss/cost in energy.

    I do expect the recirculation valve to fail occasionally, but as you say it’s pretty cheap and easy to install. I installed ours in a similar location, under the farthest bathroom sink with easy access.

    Nice to hear you also have an infrared thermometer. You must be a fellow geek.

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