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Saving Water the New-Fashioned Way

By Bill Nye | Published: May 12, 2010 – 9:15 am

My neighbor Ed thinks he’s got an edge on me right now because he installed a “gray water” reclamation system. Gray water is the term civil engineers use to describe wastewater that is dirty, but not too dirty. We’re talking about water from the dishwasher, the clothes washer, and maybe the shower. Well, not so fast. See, the idea is to save water. But apparently, Ed’s using a whole lot of electricity just to run his fancy schmancy pumps. And the water kinda’ stays gray. His wife is not so happy with it unless he gets it extra, extra clean. So, it might be costing him more in electricity than he’s saving by reclaiming his gray water.

But wait; there’s more: I’ve just installed an “on-demand hot-water recirculation pump.” That’s right my friends. This gizmo will help me stop wasting water and save me a great deal on my water bill.

Here’s the idea: I have two inline (also called “tankless”) gas-fired water heaters. I have one on each side of the house, one for the kitchen, and one for the bathrooms. The idea is to reduce the amount of water you waste waiting for the water to get hot. The inline heaters work well, but they have a small, but not insignificant, problem. Once you open the tap, or faucet, it takes quite a while for water to flow from the inline heater to where you’re standing waiting to wash your hands. All that cool water runs down the drain, unless I take the troublesome step of capturing it in small plastic pitcher– which I did for a while.

Now, when you first go into the bathroom in the morning, you press a small button. It activates a pump that drives water from the hot-water pipe, under the sink, to the cold-water pipe– from the hot side to the cold side. The button runs on just 5 volts, so you can’t get a shock. The pump keeps running until a temperature sensor next to the pump tells the system that the water has gotten hot. It takes just a few seconds. Once it’s hot, the pipe stays hot for quite a while; you don’t need the pump.

It’s like a hot water circulation loop, but it only runs when you need it– not all day or on a timer, which may or may not be on at the right time.

The trick is that you can pump cool water backwards through the cold water pipes, and everything works fine. That water ends up in the water main, where it came from. Or in my case, it finds its way to the solar pre-heated water tank. My system goes from solar collector, to holding tank, to inline heater, to sink or shower. But, with the on-demand pump, I can force water that’s not hot yet back into the tank.

Take that Begley– ha! Pretty cool… well, it’s pretty hot.

23 Responses to “Saving Water the New-Fashioned Way”

  1. Brad says:

    Very cool Bill!

    Would it be possible for you to post a diagram of your setup?

    My water heater is getting kind of old and I don’t use very much hot water as it is so this might be a project I’ll take on this summer.


  2. Brad says:

    Very cool Bill!

    Would it be possible for you to post a diagram of your setup?

    My water heater is getting kind of old and I don\’t use very much hot water as it is so this might be a project I\’ll take on this summer.


  3. Jesse says:

    To be fair, not all greywater systems use pumps. Ideally they only use gravity to transport the water to its next use. Gadgetry is no match for common sense.

  4. Kelsy D. says:

    Woot!! I’m rootin’ for you Bill! >:D

  5. Andrew S says:

    Good job Bill, Keep up the good work. I’ve seen those pumps before and it is quite brilliant. I hate it when I waste water waiting for the warm water to reach the faucet I’m currently at so I try not to use hot water.

    How much did this set up cost you if you don’t mined answering. Because I might want to do something similar.

  6. Karen J says:

    The competition you have with Ed Begley is a hoot! However, it’s great that you are both competing to live “greener” and “cheaper” in the process. I saw the episode of “Living with Ed” when the gray water system was installed and thought to myself that Rachelle is never going to like it. Too funny.

  7. Barb R says:

    I just today was telling my daughter how it is so wasteful warming the hot water tank all day and night and waiting for the hot water to travel upstairs and then found this on your site this evening. I have not seen you since— many years! Saw you on Tv tonight regarding the oil drill leak and looked you up. Raised my kids with your shows. :)
    I would love to get this hot water /cold water adapter..THINGY! great job!I am married to a Mechanical Engineer( for 26 yrs) so if you post directions make them as simple as you can.. wink

  8. Norman M says:


    I heard from a friend whose son lives in Japan that the grey water system they have running is that they wash their hands in the bathroom and that “Grey” water is then put in the toilet tank to flush! Neat way of easily using grey water!

  9. Chuck S says:

    One thing does not make sense to me. I’ve been using one of the recirculation pumps for many years, as a retrofit in lieu of a recirculation pipe, to have instant hot water. I have it on a timer to run at important times during the day/night. Question: if you are pumping water into your cold pipe, how the heck does it end up in your solar pre-heat tank which is on the hot water side?? I guess you mean that it is pushed down the cold towards the water main but cold is also getting sucked into the hot system at the same time so it goes into the solar panels?

    Cool idea and use of the recirculation pump. Mine has run for 10 years or more with no problems.

  10. annie s. says:

    hey bill i need some help on biomes and i cant find a video
    can you help

  11. Emily says:

    Just learned about this in my AP Environmental Science class!

  12. We just built and installed a solar water system on the roof of our main farm house in Costa Rica. We were able to do it with local, cheap and recycled material. We have gravity fed water from a spring that feeds coils of tubing on the metal roofing. In just 20 minuted of sun we get 150 degree water! We then dump that into our old hot water heater for storage. The system stays charged with pressure from the gravity. We are installing a second tank directly after the roofing coil so we can insure at least warm water only entering the final tanks. For periods with no direct sun we are building a wood heated convection loop to keep tings hot on the roof and in the tank.

    We used old plastic bottles stuffed with plastic wrappers and old baggies to build insulation for our hot water lines.

  13. Emily says:

    Wow, I saw something like this once, except it was for water purification and not heating, and plants did the job. Plants! Like, the little green things. And the water came out clean enough to drink…

    OMG no! Don’t tell Ed! XD

  14. Hailee says:

    Wow I had no clue that there was such thing as grey water!!!

  15. Brian says:

    Your grey water example is a great illustration about the problems facing society at large with water recycling programs, public perceptions about grey water and resources needed to handle / treat the grey water.

    Recirculation systems have to be designed carefully and installed with good oversight. One warehouse business had a hot water recirculation system that wasted huge amounts of energy. Because none of the piping had insulation along with very long runs up to a 40′ high roof, across the bottom of the roof, then down 40′ essentially, it was a vast cooling system for the hot water plumbling. The water arrived only luke warm and the heaters had to run the entire time the recirculation pump was active.

  16. Articles that cause my brain cells to activate are perfect for me. Your views gave me plenty to think about and consider. Thank you for interesting and thought-provoking reading material.

  17. Nick says:

    My grandpa did something almost identical to his house about 15 years ago.

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  19. Norm says:

    Just remember that if you also have a septic system, you need to make sure enough grey water is going into the septic to keep it healthy. If all your grey water is being recycled, then the bacteria in the septic have nothing to live on and there will be problems.

  20. John says:

    This is brilliant. I have wanted to setup solar power for awhile and I like how customized and efficient your plumbing/electricity/pumps, everything really, is!

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  22. Dave B. says:

    Saving money by using less water is a great idea. The gentleman above is correct with regards to the septic system. Now also a properly operating septic system, should allow much of the liquid to be filtered as it weeps down through the earth and back to the water aquifer deep in the earth – clean. Good for all to use, again.

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