Residual pressure at most remote connection on standpipe system if the building is sprinklered

[VVhope]

Hi All,

I am an EIT working on fire protection system. We are having class III standpipe system along with sprinkler system. I have previously done the hydraulic calculations based on NFPA 14 (residual pressure as 100 psi) as this building did not have sprinkler system before. Now the customer wanted sprinkler system too. The building is four storey high and more than 25m high. As per OBC section 3.2.9.2(4)(a), the residual pressure at most remote hose connection of standpipe system is permitted to be less than 450 kpa (65 psi) if the building is sprinklered. Is there any similar requirement in NFPA? I searched NFPA 14 and 13, but I could find anything that says similar to OBC that I can lower to 65 psi from 100 psi. Any suggestion would help.

 

[skdesigner]

The Ontario Building Code is a strange document, at least as far as standpipes are involved. The rest of the world moved to 100 psi at the hose valve what, a few decades ago? Not Ontario.

But, because it is the Building Code, it takes precedence over the referenced standards. What it is describing is a manual wet standpipe system. The 65 psi requirement is still there - it's just up to the fire department to provide it with their truck-mounted fire pump through the fire department connection, as opposed to having a stationary fire pump installed in the building that can provide 100% of the required pressure and flow without any assistance from the fire department.

 

[VVhope]

Thanks for replying. The building has automatic wet standpipe system. The water will be supplied from pump house. To calculate minimum pressure required at building grade level, Do I need to take 65 psi or 100 psi into consideration?

 

[skdesigner]

If you're in the Province of Ontario, it's 65 psi. Note also the difference between the required minimum flow rate in NFPA 14 (500 gpm for the first standpipe, plus 250 gpm for every additional standpipe, to a maximum of 1000 gpm in a fully sprinklered building) and the OBC (30 L/s, or 476 US GPM, total).

 

[VVhope]

Thank you, so If follow OBC requirement of 65 psi, water supply need not to be more than 30 L/s and I can not follow the NFPA minimum flow rate requirement.

 

[skdesigner]

You got it. Note the requirements for hose station locations as well. Once again, different than NFPA 14.