Regarding forward-flow testing, I have read that a main drain (if sized appropriately) can be used in place of other means. This was in the 2016 NFPA 13 A.8.16.2.4.2, but I cannot locate it in the 2019 version.
With that, what is the best practice for testing at the time of system acceptance? Without being able to use a hose monster, is the main drain test sufficient to ensure the backflow fully opens? Other than hydraulic calculations, how is it proven that we have an acceptable result? Thanks in advance. Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe
9 Comments
Dan Wilder
10/7/2024 08:11:13 am
If you can achieve system flow (with or without hose allowance as applicable) through a main drain (using a smooth bore orifice or other means to get a decently non-turbulent pitot reading) then yes, it is acceptable (Say a 2" drain on a light hazard system which is very possible)
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Chad
10/7/2024 08:26:22 am
Most guys put in a Tee off the riser with a normally closed valve feeding into the FDC when there is not a standpipe. We allow this for most simple systems.
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Tom Jordan
10/7/2024 08:32:31 am
We've been installing dedicated test headers in new campus buildings. In existing buildings, we're either installing a header or installing a bypass (with a supervised normally-closed control valve) around the FDC check valve. During forward flow testing, the valve is opened and the FDC is used as the point of discharge.
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Matthew
10/11/2024 08:29:37 am
Tom, I'm interested to hear your experience with the bypass method. Have you used it with a siamese connection? I could see it working with a storz but figured it wouldn't work with a siamese due to the internal clapper.
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Anthony
10/7/2024 08:50:50 am
With that, what is the best practice for testing at the time of system acceptance? Using a hose monster. But really you should be able to see with a flow switch test if there is any problem with the backflow upon install. this is not the point of backflow testing. The point is making sure nothing is obstructing the paddles.
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Jack G
10/7/2024 10:43:43 am
Agree with above comments.
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Mark Harris
10/8/2024 11:58:43 am
On flushing through the FDC what about the internal clappers acting as check valve to prevent flow out?
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Jesse
10/9/2024 08:13:11 am
I'm a little late to the party, but better late than never.
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Andre Bourgoin
10/17/2024 08:13:04 am
Adding a forward flow test connection on existing system, I would try to use the bypass to the FDC with a N/C valve (remove clapper in the check valve), or add a valve somewhere on the system. On a new system install a dedicated test connection, in the presence of a fire pump then install a combined pump/backflow test connection.
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