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.
- 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.