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Author:
mr leak (CA)
Tankless water heaters do NOT
need a TPR because there is no tank full of water to expand and create an explosion issue
Comments please AND ONLY LOGICAL REMARKS THAT MAKE SENSE PLEASE
The local building department is requiring drain pans under all water heaters which appears to be "make up things as you go" and results in a general lack of respect attitude that costs money and is not substantiated by logic
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Author:
Paul48 (CT)
Check some I&O manuals for tankless units. You may find out differently.The pan thing is silly. Simply requiring the possible discharge from the T&P to a safe location should be enough.
I don't believe they need a T&P, and I think it was probably the easiest route for the tankless manufacturers.
Edited 2 times.
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Author:
mr leak (CA)
Thank you for your reply
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Author:
KCRoto (MO)
The water being heated does in fact expand, but since the water must be coming out the other end, the excess pressure is relieved instantly. That being said, if the unit malfunctioned and the water was heated way past the set point, I can see why it is required. As Paul mentioned, it SHOULD be enough to pipe the discharge to a safe location, but whatever. As for the pan, it isn't a bad idea anyhow because tankless units should have isolation valves and boiler drains set up so that it can be delimed anyway. Having something there to catch any spillage doesn't hurt a thing. You seem to see it as an added expense, the code office sees it as cheap insurance against water damage.
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Author:
hj (AZ)
The few tankless units I have installed all came with, or recommended, a pressure relief valve, but I prefer to err on the side of safety and install a T&P valve.
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Author:
bernabeu (SC)
can't hurt, but does not help
since there is no 'storage' there will be no BLEVE from a steam 'explosion' due to a tank rupture (latent heat converting liquid water to steam INSTANTANEOUSLY)
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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
Edited 1 times.
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Author:
vic (CA)
With T&P's it's not a black or white issue. Meaning not all require them or not require them.
Most importantly is the way they are designed and have built in safety features and so on.
To me no matter what .... even if the mfr says that theirs is rated - tested - designed for no T & P I'd still install one if possible (however I've always been known to "overkill" with safety and so what do I know?).
In any event ..... as stated before .... make sure to check with or read the manufacturer.
Best to NEVER assume that ALL tankless water heaters don't require a T&P as you'd be assuming incorrectly.
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Author:
hj (AZ)
IT goes into a cxipsxc tapped tee.
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Author:
bernabeu (SC)
thank you, vic
sometimes I go a little too far
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
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