Water conservation: whole house instant hot water recirculation system

Water conservation: whole house instant hot water recirculation system

Grundfos Instant Hot Water Recirculation System
Beyond the sheer convenience of not having to wait for hot water to arrive at your kitchen and bath fixtures, whole house instant hot water recirculation systems can go a long way to conserving water consumption.

Think how many times and how long you typically have to wait to get hot water to your fixture.  In all of that time, tens of thousands of gallons of water are wasted over the course of a year!  If you are on a public water supply, the costs of that waste can add up and during periods of drought the totality of wasted water in communities only exacerbates the severity of the drought.  Fresh water is a precious resource.  Why not conserve it, especially when it is relatively easy and inexpensive to do so.

Even with an onsite well water supply, I believe it is only prudent to conserve our fresh water resource.

To this end, Lisa and I are experimenting with a whole house Grundfos hot water recirculation system.  The system can even work with home-run manifold PEX plumbing, which is what we are using in our Passive House.

The system works with the installation of a special valve that is placed at the fixture that is the farthest from the pump which is place atop the hot water heater.

Unlike other hot water recirculating systems, the Grundfos does not require a dedicated return line, as it uses the cold water supply at the fixture.  There is a slight warming of cold water, but to my way of thinking, this is not a big deal at all.  The only places where I see cold water is important is at the refrigerator and the ice maker and the appliance is going to do the cooling and freezing anyway.

The Grundfos pump comes with a timer that can be configured to operate during certain periods of the day like mornings and evenings when hot water usage tends to be at their highest levels.   Operating costs are minimal.

Given that hot water exists in the plumbing distribution network to the faucet and shower fixtures, the capacity of total hot water technically increases beyond the amount of hot water stored in the hot water heater alone.

The complete system can be found online costing about $250-$300.  Additional valves (which may be required for large home-run manifold PEX distribution plumbing) cost in the neighborhood of $50.  The whole system should able to be installed in about an hour.

Other systems available include units from Watts and Taco.  Prices are fairly comparable.  We selected Grundfos, simply because we have already been using one of their energy efficient well pump systems.  

The amount of water that can be conserved during the year can easily exceed 15,000 gallons for a typical family of four.  That is not an inconsequential amount, especially if one considers the population.  If we all did our part, we could reduce the strain of our water demands.

Between the selection of HETs, water saving faucets (and appliances), and an instant hot-water recirculation system, I believe we have gone a long way in minimizing our environmental impact when it comes to water conservation...and you know what?  It feels good.

With little effort, big things can be accomplished.


  1. Have you measured DHW energy w/ and w/o the recirc pump? I presume that extending the heated volume into many feet of pipe must lead to more heat loss to go along with the water savings.

    I've been looking at adding one of these during a renovation, but I'm on the fence about saving water vs. using more DHW energy. Choose your poison...

  2. Truthfully, we have turned it off. I believe when it runs, it consumers about 25 or so watts, so not a lot. Yes the water takes a bit longer to come to the taps, but since it is only my wife and I and it only really comes into play when we shower (for the first one), we're not sure that it makes a lot of sense for us. That coupled with the fact that home runs, we have found are the least efficient configuration for such a system. We may need to add additional endpoints to other taps to derive the most benefit from it. So for now it is off, as we continue to monitor our energy consumption and seek to minimize it wherever we can.

  3. I'm an neophyte in this area but I asked someone at our local utility and he said these pumps are one of the worst energy wasters you can have in your house. That may be if they are left to run 24/7. Would really like to hear some definitive info on this as I too feel guilty seeing all that water run down the drain every time I need some hot water.

    1. Not much energy consumption, 25 Watts. Or about 3Kwhs per day assuming 24/7 operation. Unit can be programmed to operate at specific times of the day only, reducing power consumption even further. We found using our PEX home run system is not the greatest setup for such a unit, in practice. While hot water delivery times were reduced, we feel we would need more remote valves to assist in further time reductions. Given that we use a ground well and our hot water usage is relatively small (for the two of us), we felt its usage wasn't a priority.


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