NagromYargTrebloc t1_j6njxai wrote on January 31, 2023 at 4:27 PM

I have never understood the wisdom of insulating a few feet of hot water pipe from the tank to where it disappears into the inaccessible reaches of the house upstream. In my case, I have only about 4' of 1/2" copper hot water pipe below a finished ceiling. That only about 1 pint of water.

Never insulate cold water lines. The insulation will trap condensation and hold it against the pipe. Two things can happen: 1. Legionella bacteria can be formed, and 2. U.I.C. can happen causing pinhole leaks.

UEmd OP t1_j6npi1b wrote on January 31, 2023 at 5:02 PM

Isn't the concern that too close to the tank can potentially obstruct flue if tank is fuel heated?

magaoitin t1_j6ous9g wrote on January 31, 2023 at 9:15 PM

I agree. I have only ever insulated hot water lines when they enter an unconditioned/vented, or uninsulated crawlspace.

That being said, there is no reason you cannot insulate from the tank to the wall. Just not sure what benefit it has.

Maybe if it was new construction and you are insulating to get a zero offset heat waste for being as "green" as possible you could insulate 100% of your hot water lines, but at that point you are probably insulating all the interior walls because you already drank the Kool-Aid™ of "perfectly" insulated and sealed home construction.