Question for engineers on intake pressures?

On intake pressure how low do you pull it down when connected to a hydrant?

I am told to pull it down to 5 psi by our Assit Chief. All the training I have had for state certification said no less than 20 psi. We have poor water supply to our hydrants mostly 4 inch feeders on a loop. We have a 6 inch on the main supply with a static pressure of 65 psi on average (Town is on a hill), All the lines are from the early to mid 1950s. The most I have flowed is 350 gpm off a steamer to five inch LDH I could have pushed it a little more but not much. That was off of a dead end 4 inch.

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Permalink Reply by Michael A. Pimental on September 19, 2010 at 4:52pm

It is not recomended to run below a 20psi residual as an insurance policy. If the brass is willing to risk a truck then thats there choice. we have at fires run it down to 10psi, and even 5psi but not maintain it. if it comes to getting your brothers out of the shit you run the pump down to almost 0 like thay say risk a little to save a little risk a lot to save a lot. your pump can only move as much water as you can feed it. at some point you just need to tell the brass there out of water tell him to supply you more it's basics lol. if you get 350gpm out of your hydrant than all you can pump is 350gpm no matter how many pumps and psi you have pumps dont create water it only moves it. Good luck and stay safe out there.