Off-Grid Well Setup

Question

I have a well drilled and set up soon on my property where I plan to use completely off-grid (not tied to city power) solar array. Obviously I plan to optimize the power usage for everything that is going to be there. The well pump is one of those things.

So the well people recommend to install medium (40 gal) pressure tank with cycle stop valve (CSV) while I think I might be better off with a larger tank (80 gal) and a pressure switch (PS).

I understand that the CSV is good for the pump longevity with a continuous water usage (like showers), but I think a larger tank with PS is good for both - pump life & energy conservation (with considerable water usage). 4 people are going to live in 2 cabins on and off with each cabin having 1 kitchen sink, bathroom sink, toilet & shower. What do you, experts out there, think about it?

I am completely new to this whole thing, so I need guidance. Thank you!

EDIT: I guess I should have phrased the question simpler, like "what will use more energy CSV or PS in a well with the pressure tank setup?". That is the answer I am looking for the most. But nice to hear about alternatives as well.

Answer 1

If the terrain allows siting a tank above the level of the cabins by at least 50 vertical feet or so, put a 1000 gallon (or even larger) tank there, and run pipes up to it from the well, and down from it to the cabins. A tank on a tower can be done if the terrain does not allow, but is typically going to be cost-prohibitive .vs. one on the ground, even with longer pipe runs associated with the ground-mount tank.

That will give you ~ 25 PSI at the cabin where I assume you meant 8 feet (since you used the " which normally means inches for the horizontal distance as well, and I doubt the cabins are 200 inches apart...) below the well head (so 58 feet below the tank) and 30 at the one 20 (so 70) feet below. Which is quite decent backwoods pressure, but we see city folks cranking 60 up to 80 because there "isn't enough pressure" so you may need a higher hill if you are one of those folks, or you may need to adjust your expectations.

That way, the stored power associated with "the sun shines sometimes, but you want water other times" is stored directly as water available at pressure, and you can use a dedicated solar-powered pump that pumps any time there is sunshine and the tank isn't full, with no battery storage needed for that part of your power system. That is a HUGE win in off-grid. Battery storage is expensive and inefficient. Storing water up high is relatively cheap and very efficient. Unlike batteries, gravity does not wear out or become less efficient.

It sounds like you are building a typical on-grid pump system either way you describe it, and that is likely a mistake that will prove expensive, as there are a number of water pumping options that are fine-tuned for solar power off grid use, and a normal on-grid "well guy" may not even be aware of them, much less sell them. A normal on-grid pump setup is a huge load for a normal off-grid solar system to support - it can be done, but it's vastly expensive.

You should spend some time looking through the water pumping sections of serious off-grid suppliers (and the terms here prevent me from directing you to any, so go look for yourself.)