To me, it makes more sense to locate a backflow on the suction side of a pump. However, I have recently run across a facility with the backflow downstream of the pump (discharge side).
The main fire pump controller is connected between the the first check valve and the backflow preventer.
The jockey pump is connected after the backflow preventer.
Here's the problem: when the first check valve fails, the main fire pump continuously starts & stops because the pressure is bleeding off they the relief valve while the jockey pump remains idle.
Is this an acceptable scenario?
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9/20/2021 08:35:05 am
1) the installation of the BFP after the fire pump is not that unusual. It is easier to account for the pressure loss with the pump. Locating the BFP before the pump does create potential scenarios for low suction pressure.
9/20/2021 08:46:25 am
Agree with Glenn. Though its not my favorite, there are reasons sometimes to put the BFP downstream of the pump. Usually these have to do with the increased friction loss the BFP creates when the pump is at 150%.
We have installed backflows in a similar fashion as there are inherent issues with low suction potentially.
9/20/2021 10:34:22 am
9/20/2021 10:36:26 am
Have you tried raising the sensing line pressure start? May be too low.
9/20/2021 11:28:38 am
Are you speaking of a booster pump ?
9/20/2021 12:47:42 pm
In all cases, as indicated by other peers, it makes sense to have the sensing lines connected on the same side of the check valve / backflow preventer
9/21/2021 12:45:00 pm
This is an existing condition, so this is not exactly applicable, but I was told that it's better to have the BFP in front of the pump, as the BFP may not be rated for the higher pressure created by the Fire Pump. Just some food for thought.
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