Sunday, July 1, 2012

Plumbing Efficiency in New Construction: Using a Little Pipe to Save a Lot of Water and Energy

All of us have had the annoyance of waiting for hot water.   Whether it's to do a good job of hand washing or to get the morning shower over quickly, you know the feeling.

The conventional wisdom has always been to install a recirculation pump.   The best one available is probably from ACT:
It's a good solution, I guess the only problem is the cost, which is about $200 plus labor.

However if you pipe your hot water directly to each fixture with 3/8" pex, you have solved the problem.  But now you have to convince your plumber.

Gary Klein has developed a plumbing strategy that eliminates the need for a recirculation pump if the house you're designing isn't too damn big.  The strategy is called Structured Plumbing.  The reason it works is that there is very little water in the hot lines going to each fixture.  It's similar to "home run" piping.

Michael Chandler at Green Building Advisor has sketched for us what it means.   (Michael is uniquely qualified for that since he is a master plumber who designs and builds green custom homes)

Somewhat non-intuitively, it requires more pipe, which would be expensive with copper, but with PEX it's very easy and cheap.  PEX is very easy to work with,  especially in the 1/2" and 3/8" sizes, and is color coded.   Since it bends easily, you rarely need an elbow.   So you wind up using less fittings and more pipe.  That's OK, since the pipe is very cheap and should last 100 years.   In a small house, this extra cost is less than the $200 for the ACT pump, and it shouldn't need replacing during the life of the house.  Home Depot now sells the manifolds that make it even easier.

So thanks to Gary and Michael for giving us what will become the new standard method in residential plumbing.   If you're a builder, just hand this sketch to your plumber.  He may be a little reluctant at first, but if he's used to PEX he'll understand it quickly.   If he's not used to PEX, get a new plumber NOW.

Do you still need to insulate all the hot water pipe? Yes.   With insulation, the second person in the shower has instant hot water if there is less than 30 minutes between showers.


  1. One of the simplest ways to save both water and energy is to install water-efficient products. Conserving water reduces the demands to create and maintain water treatment and delivery systems, such as sewage plants and individual septic systems. Recognizing the importance of conserving both water and energy to protect the planet and reduce cost.

  2. Flow chart is superb to understand plumbing problem Good job Thanks for sharing this post.

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