Press. Reducing Valves Req'd for Dry Standpipe?

5/16/2024

When are pressure reducing hose valves required on a dry automatic standpipe system?

I have a project where I have been asked to evaluate an existing sprinkler system for an 8-story apartment building. The original installation falls under NFPA 13/14/20 2013 edition. The building is served by four dry automatic standpipes and a separate wet sprinkler feed. The standpipes are not combination sprinkler/standpipes.

The fire pump churn pressure is 212 psi and there is a pressure reducing valve provided for the wet system supply.

There is no pressure reducing valve for the dry automatic standpipes. The hose valves on the standpipes are the pressure restricting type. Not pressure reducing.

When reviewing the data sheets for the hose valves, it states "Adjustable restriction of pressures up to 175 lbs....at residual flow" but the valves themselves are rated to 300 psi. At normal, non-fire conditions, the standpipes have 23 psi static pressure of air, but if the dry valve were to trip for any reason, (non-fire or not) the standpipe exceeds 175psi static pressure on the 1st-7th floors.

NFPA 14 2013 states that "7.2.3.2* Where the static pressure at a 21⁄2 in. (65 mm) hose connection exceeds 175 psi (12.1 bar), an approved pressure regulating device shall be provided to limit static and residual pressures at the outlet of the hose connection to 175 psi (12.1 bar)."

Would the static pressure be considered the normal air pressure or the static pressure if the dry valve trips?

My assumption here would be that the pressure restricting valve needs to be swapped for a pressure reducing type.

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8 Comments

Anthony

5/16/2024 08:20:48 am

There are pressure regulating hose valves and pressure reducing ones. I intemperate 7.2.3.2 as requiring a maximum static pressure at 175 psi. I think to prevent initial blow back on the hose when the fire fighter opens the nozzle. This is a case where I'd use the corker 5500 SERIES NON-ADJUSTABLE PRESSURE REDUCING VALVE or the field adjustable one at the standpipe. Or I'd use a pressure reducing valve manifold as called for in 14 for 2 or more hose valves.

Steve Cooper

5/16/2024 09:33:10 am

In the snip of NFPA 14 above, it uses the word limit. When they use the word limit it makes me think they would want a pressure restricting since they don't want it going higher. But the pressure limiting valves I have seen limit 100PSI not higher.

The Croker 5500 PRV sheet doesn't state how much it reduces by. Would that affect your ability to use that? I have not used them before, but I do see a note saying they are factory set. Do you notify the company when ordering the psi requirements you have?

Dan Wilder

5/16/2024 09:47:59 am

What was the originally approved installation? What has changed that would justify the change from the (assumed) approved installation? Section 1.3 for Retroactivity provides allowances to avoid having to change already approved and installed (correctly) systems.

Is there any signage or coordination with the Fire Department concerning the static pressure being above 175PSI on initial charging of the hoses? Once they start flowing water, the pressure will drop to the more normally encountered <175PSI.

Most trained fire departments can handle these pressures initially with knowledge prior. If the SOP has changed or the responding FD/Insurance wants things changed, yes, recommend the change the valves as needed.

As to the Normal Working Pressure, the definition below (From the 2019 NFPA 14), I would say that the working pressure would be the automatic pressure one would see without use of the FDC under working conditions (valve tripped).

3.3.24 System Working Pressure.
The maximum anticipated static (nonflowing) or flowing pressure applied to standpipe system components exclusive of surge pressures.

Not specific to standpipes but some good reading.

https://nfsa.org/2022/11/08/system-working-pressure-and-fdcs/

GRAHAM N

5/16/2024 03:06:31 pm

The approved installation shop drawings show one detail of the standpipe with pressure restricting hose valves (with note: "typical for floors 1-7) and then the drawings also show a separate cross-section view of: building, standpipe, and static pressures with a note that pressure reducing valves are required on floors 1-7.

Pressure restricting valves were installed so this has me scratching my head.

Jack G

5/16/2024 11:34:30 am

Agree that the valves should be changed out to prv s. The factory set type is ordered with the pressures of your specific jobs, however I prefer the field adjustable type that the fire department can adjust.
I was involved with the Meridian fire where I made adjustment rods ( from all thread rods ) and showed the fire fighters how to open the prv s to fullly open) prvs were new to the area back then.
To no avail. We found out that fittings in the basement used to make the cut ins were only approved——- some to only 75 psi.
On automatic dry standpipes I would add ( emergency pull stations) so that when you pull them it opens a half inch valve to bleed the air. Easy to close later. ( in trim of deluge valves)

Casey Milhorn

5/17/2024 08:47:37 am

I agree with Jack on this one but also Dan to what is your exact scope? It sounds like you have been contracted to evaluate and make suggestions, and to Jacks point not a big fan of the factory set type of pressure restricting valves. That's a chance to suggest replacing these existing valves, maybe not from a code perspective but from a practical and possibly life saving perspective for the responding fire fighters.
The field adjustable are rated to take up to 400 psi and reduce down to an acceptable range approved by the actual user, the fire responding fire department. They can be evaluated on a regular basis and adjusted to match current conditions of the pump and city combined supply.
Again, if your scope is evaluate based on "is it an approved installation based on the applicable standards at the time" then I think this suggestion to change out the PRVs is just that, a recommendation but not a code deficiency. imo.

Graham N

5/22/2024 04:02:26 pm

Casey,

Since the building was recently taken over by a new owner and property management group, I was asked to restore the building fire protection to full operation and then to check compliance with the original installation shop drawings and applicable codes.

The sprinkler system has been unmaintained for over two years and was not operational when I first visited the site. The sprinkler system also has discrepancies as to what was designed vs what was installed.

The local AHJ is pretty much nonexistent despite this being a high-rise building.

To your hose valve question,

Per the listing of the pressure restricting valves that are installed, they can only restrict pressures up to 175psi. The static pressure on the dry standpipe (when the dry valve is tripped) is 210psi and then falls as you increase in building height. The static pressure (When the dry valve is tripped) exceeds the pressure restricting valves listing to restrict pressure.

My initial recommendation was the install pressure reducing hose valves or install a PRV before the dry valve for the standpipe.

5/22/2024 04:37:42 pm

That makes sense and the fact that the existing pressure restricting valves are only listed for 175 psi should trigger a recommendation by you at the very least. I would be very careful with the install of a master PRV (which actually you would need to install 2 of them in series, with bypass assembly, as shown in NFPA 14). You might end up restricting the pressure to below 100 psi at the top @ 500 gpm. Not to mention these master PRVs can be unreliable (from stories I've heard). The field adjustable pressure regulating hose valves is probably the way to go. If you are not a PE or FPE, I would highly advise recommending that one be brought in to bless the changes. Just put it as an add price in your contract and if the owner elects to not pay for that option, that at least should reduce some liability on your part. This all sounds like a commonsense solution until the PRVs aren't tested and adjusted on a regular basis in the future and a firefighter and/or building occupants perish due to owners failure to maintain the system. But in this case, it does sound like the owner is interested in doing the right thing.

Press. Reducing Valves Req'd for Dry Standpipe?

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