TPR Valve with a pex extention

Maybe I am wrong (so tell me if I am) but shouldn’t the tpr extension pipe be cpvc and not pex??
And also the sizing of the pex is reduced on the tpr valve??

Write it up for correction, Thomas.


Thank You for the response

The discharge tube must remain 3/4" I.D. to adequately handle the pressure, steam, and water should a discharge occur. The TPR valve discharge should terminate no higher than 6 inches from the slab due to the possibility of scalding, should a discharge situation occur. TPR valve discharge tubes should be comprised of a material that is approved for distribution pipe use in the home, including copper, aquapex, galvanized steel, or CPVC. Replacement of the discharge tube is recommended to be conducted by a licensed plumber or other qualified

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Looks like 3/4” PEX. Best to contact a licensed plumbing contractor before you request any changes.

Since it is required to be 3/4" and un-restricted; how many elbows are allowed before it becomes “restricted”?

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Four 90s, I believe.

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The requirement to be 3/4" means a “nominal” 3/4". That means “in name”, simply stated, a 3/4" by name is sufficient. I have read where guys go into a convoluted explanations that a 3/4" does not really have 3/4" of actual opening so you must increase the size to 1". I don’t believe that to be correct.

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Yes this is correct.

If you read the tag on the TPR this information is included. If the tag isn’t included you can go to the manufacturers website. There is nothing wrong with this installation. Contact a plumbing contractor if you are unsure but this is a pretty simple install with no errors.

It sure looked reduced to me but I defer to your plumbing experience, Martin. :grin:

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PEX always looks one pipe size smaller. I.D. of 3/4” PEX is about the same as O.D. of 1/2” copper pipe. New code in IPC requires That the use of insert fittings on TPR must be increased one pipe size. I do a lot of new construction inspections and have yet to see this enforced.

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I am confused with your last two statements Martin, as you state new code requires one size up but in the pic does it not have 3/4 insert fittings. Do the insert type fittings not reduce the ID?

A fittings that goes into a pipe is an insert fitting. An example is copper and CPVC pipe goes into the fitting so this would not be an insert fitting. PEX fittings go inside the pipe further reducing what’s already is a similar nominal dimension pipe with smaller ID when compared to copper for example. The new code made it into 2018 IPC.

Ok so as in the pic the pex pipe has fittings that go into the pipe ( that’s what I would think an insert fitting is, (plumbers!!)) which reduces the diameter making the photo in question a reduced line on a tpr valve.

The TPR discharge pipe is actually ok for the time it was installed. If the water heater was to be replaced the discharge pipe would have to follow the new requirements to go up one pipe diameter. This is if the equipment is in an IPC state as UPC states are slightly different. Again if it looks fishy just call a local plumbing contractor for advice.

Always respect your insights / posts Martin. Always helpful to hear the advice of a hands on Contractor. Plumbing Contractor from IL correct??

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Yes Plumbers local 130. I worked for Keystone Mechanical out of Northbrook IL.

Thomas write it up as “Pex used on a TPRV drain line is NOT Authorized. Drain line should be Copper or CPVC. Drain line also CANNOT be reduced in size. It should be 3/4 inch.

Be constructed of those materials indicated in Section P2906.5 or materials tested, rated and approved for such use in accordance with ASME A112.4.1.

The fifth listed material in IPC table P2906.5 is PEX! There are a total of 12 materials approved for TPR discharge pipe. Even CMI’s should refer plumbing questions to a licensed plumbing contractor if they are not 100% certain.