Depending on your elevation above MSL, you should be fine based on the atmospheric pressure.
> > On Dec 4, 2020 at 4:57 PM, <Steven Jenkins via Sprinklerforum > (mailto:[email protected])> wrote: > > > > We have an existing horizontal split case fire pump and ground level water > storage tank. The storage in the protected building is changing, and the > amount of water needed for fire protection is going up. We are changing the > tank to a “break tank”, but even then there is not much water left in the > tank after the required supply duration, only a few feet left in the bottom > of the tank. The pump is right next to the tank, so not much loss due to > friction in the connecting pipe. With the tank full, before the pump is > turned on, the gauge on the suction side reads about 15 psi, due to the > height of water in the tank. When the pump is running at 150%, this drops to > about 7.5 psi. At the end of the required duration I will only have about 1.5 > psi of head from the height of water in the tank. So if I lose another 7.5 > with the pump on, the gauge would read -6 psi. Is this a problem for > compliance with 2019 NFPA 20, or since the pump is already running does this > make the negative 6 psi gauge reading OK? 2019 NFPA 20 4.16.3.2 Thanks, J > _______________________________________________ Sprinklerforum mailing list > [email protected] > (mailto:[email protected]) > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > > > _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
