Jerry Naylis, Pump Panel Pointers for Training and Operations Webcast presenter, has answered questions that we could not get to during the Q&A for the Webcast.
Question: Any way to get the most water from a 500 gpm pump.
Answer: The answer is it all depends. Is this an apparatus mounted pump or a portable pump? And have you looked at the pump curve for that model pump?
Question: We are a very rural department. We have a lake nearby. For suctioning from the lake, anything special so that we can deliver water more efficiently?
Answer: Obviously it would help if I knew more about your drafting set up. I am hoping that you have regular maintenance to keep the suction strainer clean. Waterborne vegetation will significantly reduce the water conveyed into the pump. The suction strainer should also be kept 24-inches below the surface if at all possible. Otherwise, you will create a whirlpool effect and pull air into the pump. The size and type of suction strainer will also impact the volume of water you are able to draft.
Question: I have a TFT 1,500-gpm automatic deck gun. It has different psi settings from 70 to 120. Without a flow meter on the truck, how do I know my gpm without trying to figure the pitot tube equation?
Answer: First you need to know what pressure the nozzle is set at. Then you need to know what pressure you are pumping into the nozzle and what the tip pressure is. I suggest that you go to the TFT Web site and look at the specs for this particular nozzle for the flow characteristic.
Question: We are usually already flowing from tank once we receive hydrant water. Is there a way to tell how what gpm the hydrant is flowing besides shutting down discharges and using the percentage method with static and residual pressures?
Answer: The easiest way is to determine the tip pressure and calculate the flow using the formula acd²√p where a is the constant 29.83, c is the coefficient of discharge (suggest using 0.90), d is the diameter of the tip pressure squared, and p is the square root of the tip pressure. This formula works for all smooth bore tips. For fog nozzles, you can estimate 175 gpm for 1¾-inch lines and 250 gpm for 2½-inch lines. The total flow is what you are getting from the hydrant.