Why is this here

[Joe Reilly]

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Odd, recently on my past 2 inspections I have found a T&PRV on the exterior of the house with a threaded end.. OK, 1st off I know a threaded end is not allowed, however in both cases it does NOT go to the water heater and I have not been actually open to trace out where it goes to.

Any ideas of why it is there and where it might go to ??

[Jerry Peck]

I presume that it is on the cold water supply line, correct?

If so, they may have had thermal expansion issues causing the T&P at the water to leak frequently, and what to do with that water?

Extend a cold supply to the exterior (or just replace a hose bibb with a T&P) - thermal expansion? Who cares (they think) as it's now leaking to the outdoors.

[Joe Reilly]

I presume that it is on the cold water supply line, correct?

If so, they may have had thermal expansion issues causing the T&P at the water to leak frequently, and what to do with that water?

Extend a cold supply to the exterior (or just replace a hose bibb with a T&P) - thermal expansion? Who cares (they think) as it's now leaking to the outdoors.

Jerry - I have run across this in 2 different cities recently, and I have no idea where it comes from.

[Jerry Peck]

Joe,

Ask the local building department or water utility about them, maybe they require thermal expansion protection and that is someone's idea of a thermal expansion valve (it isn't), but one could be put there).

For thermal expansion control, there are two options I can think of: a) thermal expansion tank; b) pressure release valve which is set slightly above normal utility water pressure and releases water when thermal expansion raises the water pressure due to the water heater heating the water.

[Larry Morrison]

Or could be as simple as a weekend project with uncle George and they were short a pipe plug or other correct fitting (hose bib on the first one, needed just a coupling on the second but had a Tee and just had to use something to plug it... I'm guessing), The ACE Hardware was closed, but they had an old T&P valve in the junk drawer and used it for temporary as a plug so the water could be turned back on and just never got back to finishing the job.

Hey "if the women don't find ya' handsome the may as well find ya' handy"

[Wayne Domina]

This may be secondary protection if a PRV fails

[Jerry Peck]

This may be secondary protection if a PRV fails

Except ... if that is on the end of the T&P discharge line, then it is a "valve" and "valves" are not allowed after the T&P relief valve, and not only is that a valve, it is a valve which is "always closed" and takes temperature and pressure to release, and for temperature to reach that valve ... (that is not likely to happen) ... and for pressure to reach that valve ... (that means pressurizing a piping method which is intended for '0' psi as used, and even if used as a water supply line of 85 psi, that valve will not release until 150 psi ... which would not be good under any circumstance.

[Wayne Domina]

Except ... if that is on the end of the T&P discharge line, then it is a "valve" and "valves" are not allowed after the T&P relief valve, and not only is that a valve, it is a valve which is "always closed" and takes temperature and pressure to release, and for temperature to reach that valve ... (that is not likely to happen) ... and for pressure to reach that valve ... (that means pressurizing a piping method which is intended for '0' psi as used, and even if used as a water supply line of 85 psi, that valve will not release until 150 psi ... which would not be good under any circumstance.

I missed that he confirmed that it was a temperature type valve in his original post. It appeared that it might have been a pressure only valve.

[Jerry Peck]

I missed that he confirmed that it was a temperature type valve in his original post. It appeared that it might have been a pressure only valve.

A pressure only valve could be on a supply line to relieve thermal expansion, put not on a water heater T&P discharge line ... and we don't know what it is on ... the next step would be to verify that it is NOT on the water heater T&P discharge line (that discharge line should end in the same room or space as the water heater, and if it did, that could be confirmed. And confirming that the valve was not on a water heater T&P discharge line would go a long way toward being able to say:

'I don't know what it is for, but it is not on the water heater T&P relief valve discharge line, IF IT WAS on the water heater T&P relief valve discharge line, that would be very hazardous - however, it is not, so it is a 'I wasn't able to verify what it is for - have a licensed and qualified plumbing contractor trace the pipe it is on back to its source and determine the valves purpose, and what type of valve, if any, would be acceptable to be at that location'.

That is the second inspection he found with a similar valve at a similar location, but "why" and "what is it for" is not known.

[Richard Bushong]

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Odd, recently on my past 2 inspections I have found a T&PRV on the exterior of the house with a threaded end.. OK, 1st off I know a threaded end is not allowed, however in both cases it does NOT go to the water heater and I have not been actually open to trace out where it goes to.

Any ideas of why it is there and where it might go to ??

We used to see these quite often in the older parts of DC and suburban MD. it should be a pressure only valve set at not greater than 30 pounds , they used to be on hot water boilers that had been converted from coal to oil or gas. A lot of them were installed on systems that were originally open systems with a drain dumping out of the attic onto the roof. Now with attic remodeling and the need to push heat up to the attic some contractors modified the system into a closed system with a new boiler and added this relief at the top of the system. A good idea? No but there are so many of these that were never inspected that they are fairly common.

[Joe Reilly]

DSCN5449 (450x338).jpgDSCN5162 (450x338).jpg

Odd, recently on my past 2 inspections I have found a T&PRV on the exterior of the house with a threaded end.. OK, 1st off I know a threaded end is not allowed, however in both cases it does NOT go to the water heater and I have not been actually open to trace out where it goes to.

Any ideas of why it is there and where it might go to ??

Ok, after much further research and looking and looking, it appears that this 'Cold water relief Valve' is designed in the event pressure builds up to the point it can damage normal household components and it will 'blow' , similar to a Hot water heater T&PRV.

'Cold Water Pressure Relief Valves. The pressure relief valve is a type of valve used to control or limit the pressure in a system or vessel which can build up by a process upset, instrument or equipment failure, or fire. The pressure is relieved by allowing the pressurized fluid to flow from an auxiliary passage out of the system.'

[Jerry Peck]

Ok, after much further research and looking and looking, it appears that this 'Cold water relief Valve' is designed in the event pressure builds up to the point it can damage normal household components and it will 'blow' , similar to a Hot water heater T&PRV.

'Cold Water Pressure Relief Valves. The pressure relief valve is a type of valve used to control or limit the pressure in a system or vessel which can build up by a process upset, instrument or equipment failure, or fire. The pressure is relieved by allowing the pressurized fluid to flow from an auxiliary passage out of the system.'

Joe,

What is shown in the photos looks like a temperature and pressure (T&P) relief valve, not just a pressure relief valve (PRV).

The way to know for sure (but that 'test' handle is typically a giveaway for a T&P) is to look at the label on the valve, which is typically a metal disc under the 'test' lever. That will tell you what temperature and what pressure it is supposed to relief at.

While I have not seen a PRV (pressure relief only) valve with a 'test' handle like that before, one may exist, so the only way to know what it actually is would be to look at that label.

[Richard Bushong]

Ok, after much further research and looking and looking, it appears that this 'Cold water relief Valve' is designed in the event pressure builds up to the point it can damage normal household components and it will 'blow' , similar to a Hot water heater T&PRV.

'Cold Water Pressure Relief Valves. The pressure relief valve is a type of valve used to control or limit the pressure in a system or vessel which can build up by a process upset, instrument or equipment failure, or fire. The pressure is relieved by allowing the pressurized fluid to flow from an auxiliary passage out of the system.'

Around here we install the cushion tanks on new HW installations and most water systems now have regulators at the entry point. I know here in WV on the water system I am on the main pressure is around 120 and we all have regulators. With the lime buildup here we can almost make a living just changing out regulators.

[Tom Rees]

https://www.grainger.com/product/2XL...gnid=175663197

[Jerry Peck]

https://www.grainger.com/product/2XL...gnid=175663197

Very interesting, pressure only with a test lever.

[greg marold]

Would this not keep the pipes from bursting in winter?

[Tom Rees]

Jerry, What would an inlet type be used for.

[Tom Rees]

Would this not keep the pipes from bursting in winter?

Good question??

[Jerry Peck]

The inlet type is referring to the thread, and it also states the outlet thread type: Bronze Pressure Only Relief Valve, MNPT Inlet Type, FNPT Outlet Type

(inlet is male National Pipe Thread and outlet is female National Pipe Thread)

Would it prevent freeze damage? Depends on the pressure setting, but that states that it is factory set to 150 psi, which I doubt will offer much protection. Also, I'm not sure that will protect against freeze bursting in another location that freezes.

[John Kogel]

Would it prevent freeze damage? Depends on the pressure setting, but that states that it is factory set to 150 psi, which I doubt will offer much protection. Also, I'm not sure that will protect against freeze bursting in another location that freezes.

Hello, y'all, been offline for a while.

OP is in California, and I'm guessing, a relatively frost-free part of California?
Anyway, the ice would form at that valve first, so it won't work if we get an ice age.

It will protect from excess pressure, but there are more elegant valves for that, indoors with a discharge pipe. Some are hidden and we never see them as HI's. Cheers.

[THOMAS HORNE]

Joe,

What is shown in the photos looks like a temperature and pressure (T&P) relief valve, not just a pressure relief valve (PRV).

The way to know for sure (but that 'test' handle is typically a giveaway for a T&P) is to look at the label on the valve, which is typically a metal disc under the 'test' lever. That will tell you what temperature and what pressure it is supposed to relief at.

While I have not seen a PRV (pressure relief only) valve with a 'test' handle like that before, one may exist, so the only way to know what it actually is would be to look at that label.

Why couldn't a TPR valve be used if it's pressure setting were appropriate to the maximum service pressure of the piping in the building materials list of the Underwriters Laboratories? Yes I am really asking. This question is not rhetorical. My Dad was the Plumber. I'm an Electrician.

--
Tom Horne