# Thermal expansion



## ICE (Oct 22, 2011)

I posed this question to the engineering dept. at work and should get an answer next week.

Sprinkler systems incorporate a check valve and are a closed system.  Will the pipes in a hot attic experience a rise in pressure that warrants a provision for expansion?  Our practice is to include the provision on all closed systems. Code requires this if there is a water heater in a closed system and my AHJ requires it on all closed systems because of the expansion in the pipes due to high ambient temperatures encountered in attics, etc.

The Fire Dept. has been the agency that approves and inspects sprinkler systems.  My responsibility has been structural support, pumps and backup power, etc.  I recently encountered my first residential system and it's not all that clear as to who will be responsible for what.  Naturally I am applying my knowledge of plumbing on a sprinkler system to the same degree as I would any plumbing system.  Perhaps I can't do that.  I must say that the way it's put together looks like a Disney Engineer {Goofy} created it.  Plastic pipe, no less.

My gut feeling is that his answer will be no.  I am not aware of failures due to expansion but I think it is a reasonable question given our policy to provide for expansion on all closed systems.   Any opinions?  I also wonder if other jurisdictions require expansion protection on all closed systems regardless of a water heater.


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## Rio (Oct 23, 2011)

Realistically how hot is the hottest attic space going to be, 140, 150 degrees?


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## cda (Oct 23, 2011)

Yes the pressure will rise

The pipe is designed to 175 psi and I think tested to 300??

Some systems can be designed over the 175 psi

Cannot quote the max

Some  systems not all have pressure relief valves and or retard chambers

Not sure if the retard chamber helps with rise in pressure on the pipe

Do see systems rise in pressure on hot days, but not that much


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## permitguy (Oct 23, 2011)

I'm only familiar with the concept of providing for expansion on closed systems containing water heaters.  I've not seen a jurisdiction require it on all closed systems as you describe.


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