How to Remedy Constant High Static Pressure?

5/20/2020

My fire sprinkler system was poorly designed. Static fire water pressure is constantly at or above the relief valve rating. This causes the valves to constantly discharge. I can't rebuild the fire system.

Can I put two valves in parallel or in series to reduce pressure? Would that invalidate the system?

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5 Comments

Dan Wilder

5/20/2020 08:17:29 am

Is the system working pressure above 175 PSI or is it below 175 but the relief valve continues to leak?

If the system working pressure is below 175 PSI, change the relief valve to a higher pressure. Note taken from AGF site:

"Standard relief valves are required to OPEN in a range of pressure between 90% and 105% of their rating. The valves are required to CLOSE at a pressure above 80% of that rating." This means a 175 PSI valve will start to open at 158 PSI. Putting a 195 PSI valve on there would allow for a 175 PSI opening pressure.

If you have a working pressures above 175 there are two options (well possibly 3):

Change out all the sprinklers to a 300# rated sprinkler and verify all other system components are rated for the higher actual static pressure (some threaded fittings and valves carry a lower rating, pipe/couplings).

Provide a Pressure Reducing assembly per the MFG's requirements (typically a large valve with a smaller valve for low flow conditions). You may need to provide redundancy (dual setups). The system will need to be recalculated to prove the lower pressure is still able to provide the needed supply for the building occupancy and hazard.

The third is have the incoming supply pressure be reduced by the water municipality. This would affect every building on that supply and not likely an option but an option if it only supplies that building.

Jonathan Sullivan

5/20/2020 08:34:12 am

Awesome explanation Dan. Also this was addressed from an installation standard perspective here:

https://www.meyerfire.com/daily/relief-valve-for-wet-pipe-sprinkler-systems

if anyone wants to read.

Casey Milhorn

5/20/2020 04:15:23 pm

Yup, Dan nailed it. Surprisingly many of the sprinklers, valves, fittings, and couplings are rated above 175 psi nowadays, compared to when I started in the biz. You might already be okay, as Dan mentioned, to just simply swap out the pressure relief valve to a higher pressure. Next I would talk to the City and see what they can do to help out if the first option doesn't work. Pressure regulating/reducing valves would be my last resort. They add inspection and testing costs to you annually, are prone to failure, and could lead to early repair/replacement costs.

Stephen Aikey

5/20/2020 12:50:39 pm

Not sure I would be so quick to blame the Sprinkler Design! Sounds like the relief valve is working as designed. Would like more information as to where the high pressure supply is coming from?

Pete D

5/20/2020 08:15:31 pm

If the sprinkler design required 175 psi at a 40 ft roof elevation, it would need to have roughly 192 psi at ground level. If you had a 185 psi rated relief valve it would constantly leak. You need to look at the sprinkler hydraulic calcs to see what is required at the pump discharge, and look at the safety margin. If the additional pressure is needed in your installation, a higher rated relief valve can be installed on each riser. If the added pressure isn't needed, it may be as simple as dialing back the off theeshold on your jockey pump controller to fix all systems leaking.

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