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I just installed 15 raised beds in an off-grid plot. I want to drip-irrigate them with solar powered submersible well pump(s) and an automatic control system.

The good news is that the ground water is only 5-6 feet down most of the year. I've only had the land for 4 months so I don't know for sure. In any case, hand augering is easy and I don't mind going down 10-12 feet just to be on the safe side.

The raised beds are in 3 groups of 5. The groups are 10-15 ft far apart from each other. The groups are at different ground levels (three feet apart at most) and some of the beds in each group are at different levels (6-8 inches).

Would you:
-drill three separate wells- one for each group of raised beds?
-drill one well and run pipe between the groups?

It seems a little wasteful to drill three wells, but there are submersible well pumps that cost less than 15$. Between not needing to worry about running pipe/complex switching to make sure the flow is somewhat even, I'm leaning towards three separate wells.

Any thoughts?

ps-- we do drop below freezing for ~2-3 months during winter...
 

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You will need to run wires to the three wells or run plastic pipe to the three groups. Drill a 3/16 inch hole in the pipe, near the pump. During warm weather, put a big screw in the hole. In cold weather, remove the screw. The pump can still supply water, but when it shuts off, the water in the pipe drains back into the well. Be sure to cap off the well openings to prevent rotting mice from contaminating your ground water.
 

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I would put a hammered sand point in a central location. Drive it down about 10 feet in case the water level drops seasonally. Leave about a foot of pipe above ground level. Don't put a picture pump on it. Do seal the top after inserting a hose from the pump down the well so you don't get contamination in the well.


Next a 12 volt pump with pressure switch. Check the specs for lift height and pressure. This one has 8 feet lift height and 45 psi. It can lift the water from 8 feet down in the ground. Your current static water level is 5 feet so this should work.


A 100 watt solar panel in full sun puts out 8 amps. The pump draws 8 amps. Serendipity. If you could count on the same, or more, hours of full sun hitting the panel every day as the pump runs in a day one panel would be enough to keep the battery charged. Unfortunately there are cloudy days. Get two 100 watt panels.

Get a charge controller with a load terminal. If you hook the pump to the load terminal the charge controller will shut off power to the pump if the battery voltage gets too low. This protects the battery because it could be damaged if it is drained too far. The charge controller will turn the power to the pump back on automatically when the battery is charged up again. The downside is that if the pump is shut off the beds won't get water.

A marine deep cycle battery, like one for a trolling motor, will work fine and is inexpensive.

Distributing the water to the beds comes next. A battery operated timer will come on when and how long you program it to. When the timer turns on, the pump will come on and pump water to your beds. If the pump can't pump enough water to water all your beds at the same time you could split the output line from the pump into 3 and put a timer on each. Plumb it so each timer waters one group of beds. Program the timers so they come on at different times and allow a half hour between times so the pump can cool off.


I am not a great gardener so am not certain when is the best time of day to water your garden. From a solar electrical standpoint the best time would be mid afternoon. By this time the battery will most likely be fully charged and the electricity generated by the panels is wasted. If you water then, the wasted electricity will run the pump and it won't drain the battery.

I would drain the whole system before the freezing weather hits. You are not going to grow anything when the temps are below freezing anyway, are you?

Here the regs won't let you put your well in a heated building. It must be 10 feet away from a building. We bury the pipe from the well to the house 5 feet down to keep it from freezing. We build an insulated box over the well and heat it to keep the well and pump from freezing. Easy peasy if you have grid power. A single 100 watt incandescent light bulb keeps it warm enough but I do back it up with a small space heater in case the bulb burns out. The bulbs they sell these days don't last as long as they used to but that is a rant for another day.

I have been cogitating on how to keep the well and pump from freezing on my off grid property. I think if you took the gas valve out of an old propane hot water heater and put it in the well box, the pilot light flame would be enough to keep it from freezing. The 100 pound propane tank should run that pilot flame for a good long time. I want to put a bunch of fiber optics through the side of the box so the light from the flame shows outside the box. You could then check that the flame is burning every night when it's dark, like when you go outside for that last pee before bed. I think you would have to put a couple small holes in the box to provide combustion air for the flame..
 
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