I'll second Craig's post. There's a light industrial area in a nearby town that has the same water supply characteristics - open a hydrant for a flow test, city pumps kick on, and residual is higher than the static.
The real problem is you have no way of knowing how much water must flow out the fire hydrant (or out open sprinklers on the sprinkler system) to kick the pump on. The city may be able to tell you at what pressure drop, etc the pump kicks on. But that by itself is essentially useless because you don't know how much water is being consumed by other end-users at the time of the flow test or at the time of a fire. Ask to perform a new flow test with city pump turned off. The new flow test (no pump) may be conservative, but as Craig points out, it may also be accurate for the quantity of water your sprinkler system will flow. Ed Kramer Littleton, CO > > How are the city pumps started, based on pressure drop? Consider the > possibility that under a low flow condition of say 1-5 heads there may > not be a significant pressure drop or flow large enough to start the > city pumps. In that case I'd suggest use the non-boosted pressures and > flow. > > That would be your worst case. Now also depending on what kind of > system you have say it's a LH system, you may still not have enough flow > or pressure to start the city pumps even if you use the entire remote > area plus hose stream. > > You might want to do two calcs depending on what you find out about the > city pump's starting sequence because someone may want to know if the > system would work based on worst case of no city pumps operating. > > Plug in 100 psi static and 110 psi residual and see if you calc program > doesn't flag that as an irregularity. > _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
