Water Heater: Flexible Tube Heat Trap

Flexible tube heat trap loop
Flexible tube heat trap loop

The insulation on water heaters is pretty good these days: the exterior shell stays within a few degrees of ambient temperature. However, hot water rises, which shouldn’t come as any surprise, and convection currents can drain a surprising amount of heat out of both the hot & cold water lines on the top of the heater.

So I added heat trap loops to the inlet & outlet plumbing using flexible tubing. These are 18″ long and I might replace them with 24″ lines to reduce the angle at the water heater. Surprisingly, there’s not much strain in the tubing: it’s happy with that bend.

The guidelines say you need a foot or so of vertical loop, but even this piddly loop keeps the upper fitting at ambient temperature after a night without drawing any hot water.

In theory, you can screw heat-trap nipples into the water heater, but this heater came with something that looks like heat traps and heat most certainly still traveled up the cold water pipe. I think that had something to do with conduction from the tank to the metallic shell of the nipples.

I’ll add all the usual insulation when I’m sure everything is tight.

As always:

  • This may or may not satisfy your local plumbing code
  • If it leaks, it’s not my problem
  • If it breaks, you get to keep all the pieces
  • Etc, etc, etc.