Looking for Advice on Deep Well Pump Sizing and Depth

[grangerjs]

Hello friends! I've been stalking this forum for a few days... what a wealth of knowledge! I was wondering if I could be able to get some advice on the the proper sizing and depth setting of a deep well pump that I need to install. I plan on going the well-to-cistern route to supply a new 4bed/3bath house that we are building in rural NW Arkansas. We had to go much deeper for the well than I was hoping and only got 3gpm. Huge bummer. I've called numerous well service and supply companies across the US, as well as Cycle Stop Valves (GREAT people and very helpful!). Here are the details I have figured out already:

- 820ft total well depth
- 260ft static water level
- 6.25" PVC Casing
- 3gpm recovery rate

Plan on using:
- 1200+ gallon cistern
- Jet or Submersible pump w/ CSV (PK1A)
- Boreline Flexiriser well hose for drop pipe, 1"
- Pitless adapter (our frost line is about 2'), 1" PVC to the cistern (shouldn't be more than 20ft run, and the top of the cistern will be on grade with the top of the well)

We're managing the build of the house ourselves, so saving cost where I can is important, but I also want to prevent any self-induced issues because I didn't set my well pump deep enough, or didn't consider any of the more critical details. Service tech in the area quoted me $19-21k to do the job. After paying $24k to dig the well, I just can't do that.

I'm assuming that, since my recovery rate is so low, I should keep the pump flow rate about the same, about 3gpm. Also, the more shallow my pump is set, the cheaper wire and hose will be, and I would get added savings by running 10/2 as opposed to 6/3 farther down to a bigger pump. With that being said, I'm afraid to go too shallow and cause problems for myself (I can't think of what that might be at the moment, but I'm also not a professional).

Would you be able to suggest to me what seems like a good depth to set the deep well pump, even what models I should consider? Thanks for you help!

 

[Valveman]

You really won't know until you test pump the well what the pumping level will be, even at 3 GPM. The recovery rare is important to be able to set the pump as shallow as possible. Setting the well pump at about 400' will give you more than 200 gallons stored in the well for the pump to work with. If that 200 gallons is replenished and the well level returns to 260' in a short time the 400' setting will work. Without any irrigation or other uses a house that size can use 300 gallons a day, so it would have to recover in at least 6 hours or so. If not, you would need a larger pump set deeper. But you won't know until you try, and 400' can be a DIY job.

A 3/4HP, 5 GPM pump will supply 4 GPM from 400'. With 400' of 200# poly, long barb fittings, a flow inducer, and 12-4 wire you can hang all this from the pitless. Coming out will be heavy and need a big wheel and a tow rope to get it out, but it can be done. Not much need in restricting a 4 GPM pump. Just use a Cycle Sensor to protect it from running dry.

 

[Sponsor]

 

[grangerjs]

This is great info, Cary, thank you! I wonder if it would be better to go cheaper on the pump for now during the testing phase to ensure I'm not dropping $1800 on a pump that won't work at 400' (if I discover I would need to go deeper into the well). Does that sound right?

 

[Valveman]

Might even look at something really cheap just for testing. I found this quickly. There are probably better choices with time to look.

VEVOR 2HP 4” Deep Well Pump 427ft Submersible Pump 37GPM w/Control Box 230V | eBay

Enjoy Quick Pumping with VEVOR Deep Well Pump. Pump out your worries with ease and relax. No challenge is too big for you. VEVOR Sand Filter Above Ground with 3/4HP Pool Pump 3000GPH Flow 14" 6-Way Valve.

www.ebay.com

 

[grangerjs]

Perfect. I'm assuming I can just restrict the flow with a valve or something similar to keep the GPM at the outlet (into the cistern) to around 3-4?

Also, with the size of the casing (6.25") compared to the drop pipe, I'm thinking that I should still easily be able to get a string and floating device down there to measure the level, don't you think?

 

[Valveman]

You can restrict the flow down to as little as 1 GPM if needed for testing the well without hurting the pump. A string and a weight will just get stuck in the drop wire and pipe. Use a 1/4" poly tube for and air line and you can tell exactly how deep it is to water.