Question

Most of the water-saving items that I've seen don't allow the plumbing system to operate properly. How can I go green?

Asked by Dave w/A Better Plumbing Company
Portland, OR

I'm a plumbing contractor. What are the advantages to going green with plumbing?

Answer

David Edwards PhD

Answered by David Edwards PhD

Santa Clara, CA

EarthBound Homes

September 20, 2010

Great question. Depending on your political and personal orientation, the advantages of going green with plumbing are monetary and environmental based on:

  • savings of gas, used for heating the water,
  • and water savings, for obvious reasons.

As you live in Portland, Oregon, water conservation is not as much of a hot-button issue as it is here in California, where water waste is a four-letter word to most, especially if you live in Northern California (or Nevada, or Arizona) and you see someone in Southern California wasting water.

Getting hot water faster, hotter, and with less water wasted down the drain is the goal of green plumbing.  This can be achieved through a tankless water heater, structured plumbing systems, PEX-based home run systems, on-demand hot water recirculation systems or a central core plumbing system.

While it is several pages of descriptions to try and define all of these different types of plumbing systems, there are many online resources that can teach you what you need to do to increase your knowledge in these systems to determine the best method to use for each house or building.

Now, you mention that the plumbing systems are not operating correctly when you use water-saving items. My experience with water-saving features are that they require some accommodations when using a tankless water heater.

  • The problems stem from the reduced flow in low-flow showers and sinks not meeting the minimum flow requirements for the tankless water heater to turn on, usually 0.6 to 0.8 gallons per minute.
  • Because flow requirements while the tankless hot water heater is on are only about 0.5 gallons per minute, once you get past the initial higher flow requirements, you can turn down the hot water requirements to what fits the application, be it shower or washing your hands or doing the dishes.
  • The solution is to have the user turn the hot water on all the way in order to get the required flow flowing through the tankless water heater, and then turn down the hot water and blend in some cold water to get the desired temperature.

Other issues we have found in this realm have to do with the anti-scald valves in showers.

  • The problem is that bolus of hot water will reach the anti-scald valve as it is preset from the factory to have a low set point temperature and therefore will cause the flow of hot water to shut off quickly when the 1st initial bolus of hot water reaches it.
  • This then slows down the flow of hot water enough that it no longer meets the minimum flow required by the tankless water heater to keep the water heater on.
  • When the tankless hot water heater shuts off, the hot water stops flowing and you get a cold burst of water in the shower. Not that it is good at anytime, but it is especially bad when it is your first shower in your brand-new bathroom or your new custom home.
  • The way to stop this problem is to turn up the default temperature on the antiscald shower valve so that the valve does not turn off the hot water flow when the hot water from the tankless gets to the valve.

One problem we had with our model home was reducing the flow in the fixtures to 0.5 to 1.0 gallons per minute. As you can imagine, with the 0.5 gallon per minute flow restrictors, the tankless water heaters never turn on, even if you are running just hot water. This can be aggravating, to say the least. The only solution is to increase the flow, or go to a tank type water heater or a recirculation pump with a high enough flow to start the tankless.

Lastly, while this may be obvious to some, if you do nothing else in the house except put on low-flow aerators or low-flow shower heads, you are going to get a reciprocal increase in the amount of time it takes to get hot water to your fixtures because you still have to evacuate all the cold water that is in the hot water line from the fixture to the hot water tank or heater. 

Again the only solution to this is to install an on-demand controlled hot water recirculation system, or to reduce the diameter of the pipes leading from the hot water heater to the fixture, which is the philosophy of the PEX-based home run type plumbing system.

I have been installing green plumbing systems for years and never have any callbacks anymore -- largely because I went through all these problems on my own house first and learned from my mistakes.

Here's to hoping my mistakes help you not make them. Good luck.

Tagged In: tankless, water saving

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