Plumbing – energy conservation (part 2)

We covered the issue of structural waste in a plumbing system. We minimized the energy losses (maximized the energy efficiency) within the plumbing system. But we still will have to wait for hot water, although it may only be for a few seconds. This is where behavioral waste comes into play.

Managing behavioral waste

What exactly is behavioral waste? Say you want to take a shower. You turn on the tap and get distracted while waiting for hot water (you check your e-mail, make a phone call, you name it). Before you know it, too much water and too much thermal energy went down the drain (pun intended).

There is a quick fix for this scenario, the ladybug shower head adaptor, a product by Evolve.

It appears that behavioral waste is primarily driven by the amount of time we have to wait for hot water. The shorter the time-to-tap, the lower the potential for behavioral waste.

Here are the strategies we have covered so far that result in a reasonable time-to-tap:

  1. Compact and efficient layout of the plumbing system: Keep the pipe runs as short as possible.
  2. Material choice: If possible, use tubing with the least potential for initial heat loss.
  3. Pipe insulation: deliver hot water effectively to the point of use.
  4. Pipe sizes: minimize the tubing size and thus the volume of water in the plumbing system.

(Almost) instant hot water

If, despite these strategies, you still have to wait too long for hot water, or you cannot implement some of the strategies, you may want to look into an instant hot water solution.

Metlund has a system on the market that meets our water and energy conservation goals.

It is a small circulation pump that is installed at the farthest fixture in the system. The pump is activated with a push button, upon which it begins to draw water from the hot water line. The pump turns off the moment is senses a slight temperature rise in the water temperature.

The cold water the pump has drawn until now is either pushed into a dedicated return line to the hot water storage tank or pushed into the cold water line, thus no water is wasted.

Because the pump is located at the farthest fixture in the system, all other fixtures located along the branch will get primed with hot water up to the twigs. The water volume in the twigs is so small that hot water should arrive within one cup (see also table in previous post) – or almost instantly.

We are seriously considering to try the Metlund system. It would improve our overall water and energy conservation. Those savings will at one point pay for the equipment.

About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

One thought on “Plumbing – energy conservation (part 2)

  1. My personal solution to the problem of wasting water while waiting for hot water is twofold: running water at a trickle instead of full-force, and using a bucket to catch that trickle until the water is hot. I then use that water (less than 1 gallon per day) for watering plants or rinsing down the shower/tub after use to minimize later scrubbing. It’s not a universal solution, but it helps reduce our water waste.

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