Had the well drilled for our house under construction last week. The driller expected to go 300-400 ft and get 2-3 gpm in our area. We got lucky and hit a 5 ft thick cave/void at 40 ft that the driller thought was making 20-30 gpm. He wanted to go ahead and drill to 80 ft but when the drill passed more than a couple feet into the cave he quit getting anything back up the casing and pressurized the cave system. Anyway, we eventually got it drilled to 49 ft...4 ft past the bottom of the void. We put a 4" screen/liner inside the 6" casing all the way through the cave. Cased to 34 ft. Static came up to about 20 ft. Currently using a 10gpm pump at 35 ft to clear the well up, pumping 15 gpm free flow. I can pump 6-7 hrs before the water level drops down to the pump at 35 ft. The driller wants to keep the pump above the cave, but I'd like to have access to all that extra water. I'd like to have the capability to pump 20-25 gpm to supply a fire sprinkler system if it's ever needed, but don't need that much for normal use. I was thinking about a grundfos sp pump, either 16 or 25 gpm model with a CSV. I think one of the 16 gpms could provide the 20-25 gpm range at such low head pressure in case of fire? Any suggestions? Thanks, Adam
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A 16S07-8 can pump 20+ GPM wide open from that depth. Adding a CSV would allow you to use as little as 1 GPM without cycling the pump. The CSV is a good way to be able to use 20+ GPM when needed and still be able to use that big pump for a 2.5 GPM shower or other stuff.
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