Screen size, sand, and water volume on new well

[TJanak]

I've always been fascinated with water wells and worked on them off and on over the years on places I have lived. Now I finally need to have one drilled for a house build and want to do it right. I'm talking to two local guys and have a few questions. But first a few details:

Wells in our immediate area are 160-200' deep. We have one our place that was not in commission when we bought it. I put a 1/2 HP pump in it on 100' of schedule 80 because that's what was left there after they pulled it. I don't remember the static level. Don't know who drilled it either, so no details. But it make sand, enough that the previous owners added a galvanized settling tank before the pressure tank. Seems to be pretty fine sand. I guess it helps some.

I'm assuming (being told) I need 20 GPM to run a decent irrigation system plus the house. Two drillers both quoted me 1 HP Goulds pumps. No CSV but we'll work on that one. 4" PVC wells. One uses 0.006" slots (machine to make his own), the other uses 0.008 slots. The one using 0.006" slots says his wells in my immediate area make around 50 GPM. The other guy who uses 0.008" slots says his around me make up to 100 GPM. Not a big deal but I'd like the option someday of irrigating a larger area and maybe upgrading to a 2-5 HP single phase pump, and 80 GPM would sure be nice.

Does this 0.002" difference have any significant bearing on how much water the well will make?

Do I risk making more sand with the 0.008" slots versus the 0.006" slots? Both guys sounded like well making sand is not very common here, but can happen.

Both guys are similar in price and come recommended locally.

Thanks,
Travis

 

[Valveman]

Normally a sample is taken of the sand and the slot and gravel pack is sized accordingly. Making his own slots? Usually this means the thickness of a skill saw blade and is not the best way to go. 4" casing is a tight fit for a 3.75" pump. I would use 5' or 6" casing, especially if you someday want to use a larger pump. I don't like 4" casing even for a 10 GPM pump.

 

[Sponsor]

 

[TJanak]

Cary,

Maybe they do look at the sand and size accordingly, but I think everything in my immediate area must be pretty fine, hence they both use the smallest slot they can get/make. The one guy said "machine" for making slots and at 0.006" I don't see how a person could do that with a skill saw. Dang, that would be a boring job...

Everything around here is 4" casing. I asked about 6"and he said he can drill me three 4" wells for the price of one 6". Can't spend that much right now, though I agree a 5" or 6" would be better.

I guess I'm just wondering why the two are quite a bit apart on the GPM their wells usually make. They both drill all over our peninsula and easily within a mile of me.

 

[Valveman]

I guess 4" casing is pretty common in that area. Just doesn't make sense to me for a 2o GPM pump, much less a 50 or 100 GPM. As long as the well makes enough water, doesn't make sand, and the pump is set above the perforations it will be fine. Both drillers are just guessing. Nobody will know how much your well will make until it is tested.