There has been a lot of discussion on this post regarding forward flow test connections.
NFPA doesn't address sizing of this connection. The project I'm currently working on is strictly sprinkler with Light and Ordinary Group 1 hazards, with no standpipe connections. The maximum expected flow is 250-300 gallons per minute.
The engineer is showing a 2" forward flow test connection piped to an open fitting on an outside wall. I know that fire pump tests are frequently conducted using 1 3/4" nozzles and easily achieve 250 gpm readings.
Does it make sense that a 2" connection would be adequate in this instance?
Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
5/26/2022 07:21:02 am
It is good to note that the most recent edition of NFPA 13 does have a prescriptive requirement of one 2.5" hose valve per 250gpm of system demand. However it also states that alternative means may be provided as long as the assembly can provide the required flow and doesn't require any modifications to the system arrangement to run the test.
5/26/2022 07:34:20 am
Oh, and since this is the topic of the day. It drives me nuts that the NFPA 13 annex material for these test assemblies still mentions piping the discharge around the FDC check valve with a bypass as an optional arrangement. There really is no justification for this to still be acceptable.
5/26/2022 08:19:05 am
I've only seen a check valve bypass when the FDC is a Storz connection, so no worry of a siamese clapper. Otherwise, I suppose you could removed the siamese to achieve the same thing.
5/26/2022 08:21:02 am
my state construction office (SCO) requires (2) 2-1/2" hose connections for forward flow testing @ 500 gpm (3 for 750, and 4 for 1000)...etc ...
5/26/2022 08:23:41 am
5/26/2022 08:34:45 am
If any of you are on NFPA 13 committee maybe it makes sense to talk about changing main drain form 2" to 2-1/2" to be both drain and flow connection on a light or ordinary hazard occupancy. Flows greater than 250 would need additional connections as noted above.
5/26/2022 09:46:32 am
Anyone can submit a "Public Input" (PI) but plan on a 3-5 year process for it to make it in (I'm not on a 13 committee but on 3 other NFPA's and the E&S for NFSA and we are in discussion for the 2025 editions and beyond). You can also tap into your local/regional AFSA/NFSA reps to have them submit something, but be prepared to provide justification and any testing support you can provide.
5/26/2022 10:09:53 am
The table for drain size in NFPA 13 states that you can use the size for the drain prescribed based upon riser size "or larger".
5/26/2022 08:56:43 am
I'm late to the party again. Eric had an excellent response, and I would echo what Alex said. We typically use a 2.5" valve for every 250-gpm. Yeah, you could get 300-gpm using a 2". I would try to have them authorize the 2.5"
5/26/2022 10:38:00 am
Has anyone found the original rational for this modification of the standards? That is to require a full forward flow.
5/26/2022 11:31:11 am
From a brief archive search on NFPA.org it looks like the requirement to forward flow testing backflows was brought into NFPA 25 in 1998 (I can confirm it is in my 2002 paper edition sitting on my shelf). Below is the link to the Request for Proposals for that edition with the new language starting on page 13.
5/26/2022 05:53:55 pm
5/27/2022 08:06:25 am
As an AHJ, we use the annual forward flow with the pitot measurement to compare the available GPM to the engineered requirement on the hydraulic plate. We want to ensure there is adequate water supply. The static and residual pressures are measured separately using the main inspector test drain. For older systems, we require the installation of one 2.5" hose valve for each 250 GPM.
5/27/2022 09:23:53 am
This brings up another great topic of discussion.
5/31/2022 10:42:33 am
ERIC R - I agree with the misinformation on some hydraulic placards. I have seen wrong street addresses, missing data, and inaccurate flow rates. As an AHJ we also really dislike the newer trend of using stickers instead of permanent metal plates for the hydraulic information. The stickers sometimes fall off the riser, are really not considered permanent, and can actually get painted over when they are placed on an adjacent wall instead of on the riser as required.
Leave a Reply.
Subscribe and learn something new each day:
Top April 2023 Contributors
Get 100 Days of Free Sample Questions right to you!
PE PREP SERIES