Upgraded from a shallow point well (10’) to a deeper well last week. I really trusted the guy who put it in…but now I have some reservations about what he did…and what the other guy who put in the pump and hooked it up did (next message).
Most of the houses in my area have wells in the 90’ range. One has a very deep well, 350’, it seems like he got ripped off.
My well came in at 58”. He used his smaller rig to put it in. He pounded 3 20’ long 6” still casing into the ground and kept checking the water/substrate with a big tube with a check valve he would lower into the well.
When he bid the job, he estimated it at 100’ (I would pay less if it came in shallower) and said I may or may not need a “screen” which would cost $1,000 if I did need it, based on his assessment.
He started getting more water somewhere over 40’…. Much fine sand. He kept going deeper till mix of sand/fine gravel. He went deeper to be in better sand/gravel. He had a cool looking set of brass trays stuck together to measure the fine-ness of the sand/gravel. The substrate was held back at various levels of screen and a small amount went to the lower very fine screen.
He determined by that what grade of screen he needed (a number 12 I think). That went down the casing then…. And he pulled the casing UP so that the screen would be exposed below the casing.
Driller said flow about 30 gpm. But he rated it on the paper to the state as 15 and marked it as that under the well cap. Said he did it so state wouldn’t ask for higher rate permit (commercial vs. residential flow). Later…. The pump installer brought a 15 gpm pump with him….. but at 110v. I wanted 220… which he said he goofed at and left at shop. Had his installer run back and get the 220v one…. Which ended up being 12 gpm. He said that is rated at 150’ deep well, and at shallower it will pump much more.
QUESTION # 1 - Did he stop drilling early (60 vs. 90) and got a well with more sand cause he didn’t go deeper into more gravel content? …. And the screen let him do this? (and the $1000 price still got him profit vs. charging for more drilling).
QUESTION # 2 - What’s with needing 15gpm at one point… but a 12 gpm is just fine at a later time?
Last edited by krosspen; 10-01-2010 at 10:17 AM.
Last edited by Thatguy; 10-01-2010 at 02:59 PM.
Pressure= 50 PSI
Equiv Head= 174 feet
Flow rate= 12 GPM
Pump eff= 100 percent
Power = 0.53 hp
That seems cutting it pretty close. I don't get it. Can you post the pump specs/curves for this pump?
On the 350' well, it would be more informative if you had a map of well depths for the area surrounding this deep well. Perhaps the aquifer characteristics change rapidly over short distances. If the owner knows about the 90' wells nearby I guess he would be asking the same question.
Last edited by Thatguy; 10-02-2010 at 07:49 AM.
Sounds like a careful driller. The pump motor is likely a 1.3 or more SF and can handle the overage if those calc's are correct.
This "10 and 12" GPM is only a broad guide. Its fairly meaningless without the pump chart - curve- for that model pump.
Sounds like you are okay to me.
The screens are Johnson Sieve Analysis. I'm impressed, many drillers don't know what they're for. I'd say you got a good well and pump installation. The pump is probably a 15 gpm pump. That doesn't mean what gpm's that pump is going to pump at your pumping level. I'd say everything was done properly.
The driller was probably right about the well supplying 30 gpm but stated 15 gpm on the well report and the well cover because of state regulations Residential/Commercial. Most state regulators don't understand wells and interpret regulations to their understanding. You're OK!
Porky Cutter, MGWC
(Master Ground Water Consultant)
Your pump is rated at 12 gpm @ 150'. Meaning the water level in the well is @ 150'. So when the water is higher, like in your 58' well with a static water level probably like 10', the pump delivers more than what it can lift from 150'. Just like your car burns less fuel with a tail wind rather than when you drive into the wind.
Question, wasn't the goal here to get a good gpm volume of water, at or before 100' depth in your new well?
Well that's what ya got! And the guy protected you from an overbearing government that would have charged you more. Your incorrect assumptions are making you feel bad. THINK instead of feeling that you got ripped off along with your neighbor. Why not assume you got a good well and pump install? You guys have no proof you were ripped off. I bet the guy with the 350' well approved the driller going that deep.
"You guys have no proof you were ripped off"
The OP is asking a question, and not [yet] making a statement.
From the replies I guess it is "more likely than not" that the OP is not getting ripped off.
Still, I'd like to see the pump curves for this 1/2 hp pump.
hp = (HDxGPM)/3956
100 % efficiency assumed
Head= 150 feet
Pressure= 50 PSI
then, equivalent head = head + (pressure x 2.31)
Equivalent Head= 266 feet
Flow rate= 12 GPM
Power = 0.81 hp
If I read the catalog specs correctly, no 1/2 hp pump at Grainger can do this.
Last edited by Thatguy; 10-04-2010 at 12:32 PM.
Most pump curve charts from the mainstream pump manufacturers (Goulds, F&W, Meyers etc. etc.) use feet of TDH (total dynamic head), it is usually stated vertically along the left edge of the chart. Drillers and pump guys usually go from memory due to experience. In this 58' well a 1/2 hp 12 gpm is a good choice but as always that depends on the peak demand flow rate requirement of the building.