Low Yield well - smallest possible submersible pump?

[Btrouse]

Hi, long time reader, first time poster here.
I am designing a residential water system for my family's home build next summer, where I'm the owner and the builder. We're planning a 3Bd/2bath, 1500 sqft home located above the well 60' vertically and 200' away horizontally. The water level in the well is 30' static, and drops to 50' when pumped at 3gpm, 65' when pumped at 4 GPM. Our well is 82' deep and has a 5' section of screen from 77-82'.

I'm trying to design a well water pump and cistern storage system, along with a separate pressure system to feed 2 frost proof hydrants and eventually the home.

For the water storage side, I was thinking to place the pump inlet at 65', and use a float switch to turn on the smallest submersible pump I can find (1/4 HP or 1/2 HP). then, because I'm filling a relatively large volume ~600gal cistern = 3hrs of runtime @ 3gpm, i was thinking to wire in a cycle sensor as run-dry protection. Seems like people often put one check valve down near the pump, although I'm not sure that i need one since the pump is submersible and its top filling a cistern... I don't think i could start a backwards siphon even if i wanted to.

Thoughts on omitting the check valve? I'm thinking no check valve allow the water to drain back to 30' static level and that could be a benefit for frost protection.

Next, is there such a thing as 1/4hp submersible pump? I did find a cheap 2" China pump from a importer/distributor in FL. According to the pump curve i can achieve 3gpm with 75ft of head pressure and operate the pump in an efficient region (some back pressure, but not too much). https://www.pumpsupermarket.com/product/2-submersible-pump-5-2-gpm-3-wire-121-ft-110-220v-0-25hp/

The other pump choice would be 1/2HP from any of the reputable manufactures, but any of those pumps would require ~150psi in the drop pipe, so i could achieve 3gpm and hopefully not run my well dry.

Next question is regarding frost protection:
The local building department says the frost depth is 24", but the local irrigation pipe supplier recommends 5' waterline burial, and as evidence they only sell 5' and 6' woodford frost proof hydrants! Cistern manufacturer says as long as the bottom of the tank is below the frost line then natural convection will keep the water from freezing. So how do I make connections at the top of the tank without fear of freezing? Do i need to install a bleed valve or weep hole inside the well casing then maintain an upward slope between the pitless and where the pipe enters the top of the cistern?

Same question on the pressure side, how do i keep the pressure tank and pressure switch from freezing? Maybe the only viable option is to build a well house (which i really don't want to do). I could maybe over-excavate the hole for the cistern to sit in and try to keep all that stuff in that same pit.

Lots of questions here, thanks for any and all advice.

 

[Valveman]

1/2 HP is the smallest sub motor made these days. A 10 GPM, 1/2HP will be less expensive than a 5 or 7 GPM, and will only have about 90 PSI back pressure when throttled back to 3 GPM. They can be throttled to as little as 1 GPM without hurting anything, but a Cycle Sensor is still a good idea as the well can still possibly be pumped dry.

Draining back to the well to prevent freezing is ok. But don't remove the check valve or the pump will spin backwards. Just drill a 1/4" hole in the check so it can drain slowly.

Keeping everything under the frost line is the only guaranteed way to prevent freezing. The top half of the cistern and fill pipe with drain back system can be above ground. But bury the bottom half with pipe connections and pump below the frost line or put in a heated well house.

You could also use a submersible in the cistern for a boost pump. That way it would not freeze. You could insulate and heat tape the discharge pipe coming out of the cistern and going underground. Then the pressure tank and switch can be in the main house where it will stay warm.

 

[Sponsor]

 

[Btrouse]

Thanks for the input Valveman, I appreciate it.

I never thought of using a 10gpm pump to achieve 3gpm desired flow, I guess it doesn't develop as much pressure because the impeller stack is running in a much less efficient zone? I suppose, for example the 5SQE05-90 seems to just have fewer impellers, so it develops both lower flow and lower pressure, it would probably work fine too, it just costs a lot of $$$ compared to 7CS05 or 10CS05. Overall it seems like your recommendation is to avoid the 1/4 hp pump from CH. I would never pay somebody to install a cheap pump like that, but I was considering doing it myself since the labor is "free".

I didn't mention this in the original post, but I do have a 240V 100A sub panel 20' from the well head already. I do like the idea of using a submersible in the cistern for the pressurized system. I was imagining mounting it horizontally with a flow inducer. But if i'm interpreting you correctly about placing the pressure tank and switch in the house... the only way to do that is to have a long electrical run between the pump (in the cistern) and the pressure switch (in the house) which are 300' apart. As far as I know, its not really recommended to mount the pressure switch near the pump and put a pressure tank 300' downstream inside the house, right? Something to do with flow losses between the two can cause the swtich to flicker on/off/on/off.

I guess 2 pressure tanks could work, a small one near the pump buried underground (fiberglass wellmate?) or maybe one of those smaller inline tanks meant for VFD systems. Then a larger pressure tank closer to 80gal inside the house to actually give the correct drawdown for the system and control pump cycle time correctly.

I don't mean any offense to the CSV1a system (I think the system seems really great actually), but I wasn't planning to install a CSV or (VFD for that matter) on this house. I was planning to live with the pressure variation between 40-60psi and just spec an larger pressure tank.