PTRV Piping -UPC 608.5

[righter101]

State of Washington uses UPC for plumbing, not IRC. My question stems from residential construction, but may not be limited to res.

Question: If you have 2 water heaters, is it permissible to use a common, upsized PTRV drain piping? 2 relief valves piped in to a single discharge pipe, that then goes outside. For instance, if you have two 3/4 inch diameter pipes, can you hook them in to a single one inch for the remainder of the pipe run.???

I have heard opinions and arguements that if you upsize the pipe after they join, it would be able to accomdate the flow of both pipes, in the unilkely event that both units failed.

The UPC says it shall "extend from the valve to the outside of the building".

The IPC and IRC specifically prohibit it.

Just wanted to see what everyone's thoughts are on this situation.

thanks

 

[pwood]

i would say no to joining the two together. you said it above.

 

[JMORRISON]

I have allowed it. Commercial job got in trouble with State Boiler Inspector (water heaters are boilers in certain commercial applications and require permits and inspection by State) months after final as they use NFPA which prohibits joining of PR piping. This section also states no part of pipe be subject to freezing so can I really discharge to the exterior? Here is excerpt from WA State Plumbing Code:

608.5 Relief valves located inside a building shall be

provided with a drain, not smaller than the relief valve

outlet, of galvanized steel, hard drawn copper piping and

fittings, CPVC, or listed relief valve drain tube with fittings

which will not reduce the internal bore of the pipe or tubing

(straight lengths as opposed to coils) and shall extend from

the valve to the outside of the building with the end of the

pipe not more than two (2) feet (610 mm) nor less than six

(6) inches (152 mm) above the ground or the flood level of

the area receiving the discharge and pointing downward.

Such drains may terminate at other approved locations. No

part of such drain pipe shall be trapped or subject to

freezing. The terminal end of the drain pipe shall not be

threaded.

Exception: Replacement water heating equipment shall

only be required to provide a drain pointing downward

from the relief valve to extend between two feet (610 mm)

and six inches (152 mm) from the floor. No additional

floor drain need be provided.

 

[righter101]

JMORRISON: Do you know which NFPA reference prohibits joining the 2 pipes?

I would be curious to read it.

That is curious about the "subject to freezing" portion, how it is supposed to go outside....

 

[JMORRISON]

Sorry, wrong code. L&I use ASME. "Code, ASME" shall mean the boiler and pressure vessel code of the American Society of Mechanical Engineers with addenda thereto made and approved by the council of the society which have been adopted by the board of boiler rules in accordance with the provisions of RCW 70.79.030.

 

[righter101]

JMORRISON, thanks for your feedback. Do you have an excerpt from the ASME that discusses this?? I don't have any of their books in my collection and they are not viewable on line. I would like to glance at it and possibly use it as part of a formal interpretation.

Thanks.

 

[Glennman CBO]

I have allowed it. Being that it is a closed system, the blow off from one would not affect the other. They should be able to discharge at the same time, but it is highly unlikely that they would. It is not allowed in the IPC, but it is not specifically forbidden in the UPC.

We don't recognize the plumbing section of the IRC, as it is superceded by the UPC. I am in Washington State as well.

As far as freezing is concerned? We allow them to terminate at the exterior wall between 6" and 24" above grade with elbow turned down. The is no water in the line, and it should be installed in such a way that water would not accumulate in the line if it was to blow off. If this is not possible, then they can insulate the line similar to any other water line in a crawl. The final termination elbow could not be protected from freezing no matter how it is installed. Even if it were insulated, the open end would still be exposed to the freezing air. Common sense applies here.