How much of a water heater’s *cold* line should I insulate?

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Borisj

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Hello, I’m installing an electric tank water heater (Rheem Marathon) in a conditioned space. The hot pipe will be insulated all the way.

But how many feet of the cold (supply) line should I insulate? The pipe for it goes up 6in, sideways 8in, then down 6 *ft* through a floor.

CA requires insulating the first 5’ (p. 25 here), but couldn’t find anything in IPC. I’m looking for best practices more than a code citation though. I’m guessing the need for this has to do with insulating the part of the pipe that may become heated by thermosiphoning… and with my pipe route, that’d probably only be a couple feet, right? Let me know what you think, and thanks!
 

Breplum

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Couple 2-3 feet is adequate. some water heaters have some form of thermal drift prevention, but some not. The methods can be tank nipples with floating ball, small rubber 'check' valves at the tank threads or nothing.
 

Borisj

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Couple 2-3 feet is adequate. some water heaters have some form of thermal drift prevention, but some not. The methods can be tank nipples with floating ball, small rubber 'check' valves at the tank threads or nothing.
Thanks! And thanks for saying "couple-2-3," takes me back to my decade in Chicago :)
 

Jeff H Young

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Yep 5 ft is the rule I dont know if IPC requires it but . I just follow 5 ft, comes in 6 ft length so i use a length. Im not anal about it but If I have the material and access to at least 5 ft I think the 2 or 3 ft good enough too but like to meet code so someone that sees it like us knows we do it right
 
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