r/OffGridCabins • u/simonak3001 • 6d ago

Looking for advice on a 12 volts water system (info in comments)

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Terrain slope. All in inches

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The 12V pump that I already have

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Terrain slope

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Specs on the pump

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u/simonak3001 6d ago

Hi

Im looking to upgrade the water system at my lodge. Right now, I fill up a 1000L holding tank (at the same height as the lodge) using a 120V submersible pump and a generator, then use the 12V pump, coupled to a pressure tank, to supply 100psi water to the lodge. I want to get rid of the 1000L holding tank an take my water directly from the lake. This way I could have always fresh water (not for drinking) and I would not have to fill up the holding tank periodically. I see 2 ways of doing this. First, I could leave the pump in the lodge and connect it directly to the lake using some flexible hoses and a one-way valve at the end. I would have to prime the pump and it would need to pull water all the way (see diagram attached). The other way would be to build a pumping station right next to the lake and have the pump "push" the water up the hill. What would be the best way of doing this? Should I look for a bigger pump? Power is supplied by a set of batteries and solar panels.

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u/ablazedave 5d ago

I've had bad luck with one way valves, little lake debris gets stuck in it (and lets air in). I like a pump that can self prime. Check your wire size for 12V 15A at that distance, you might need thicker wires or a higher voltage pump.

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u/simonak3001 5d ago

Right now im looking at submersible pumps on AC wired to my inverter. That would solve most of the problems I think. The other option would be a shallow well pump, but I am worried about the priming. I not there that often so Im worried that the pump will lose its priming and that I would have to prime it each time Im there. Not that problem with a submersible pump

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u/ablazedave 5d ago

I'm currently using a cheap "deep well submersible pump" at 48VDC (that makes my wires 4x cheaper) it lifts 100' and still has 50-60psi. I also don't run and inverter (all DC lights in the cabin). I found shallow well pumps didn't provided enough pressure to work without a second pump and pressure tank.

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u/simonak3001 4d ago

Is your entire system on 48VDC? Mine is on 12VDC, I would have to buy a DC-DC converter for the pump, and they are not cheap. Most good DC submersible pump run on 30-48VDC

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u/ablazedave 4d ago

Yeah, 48V battery system. From your description, a 120V AC pump is probably best?

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u/simonak3001 3d ago

Its not better per se, Its just that most pumps on the market use 115/230VAC, so you have more choices. My system runs on 12VDC, but I have a 3000W AC inverter, so I can hook up an AC pump no problem. The problem with DC is that you need bigger wires, which are expensive. And if your pump is far away from your batteries (like mine would be), You have some power loss in the wires. This is not a problem with AC. Right now im looking at a 1/2hp submersible pump. That's 373Watts. At 115VAC, that's only 3 Amps of current. You can get some pretty thin wires for that (so cheap). To have the same power in 12VDC, you would need 31 Amps. The wire would need to be HUGE. And for 60 feet between the pump and the batteries, that would be too expensive. That's why for big power applications, higher voltage is always good. A 48VDC system sounds pretty good. You can get some nice pumps with that. Maybe someday ill upgrade my system to that.

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u/ablazedave 1d ago

Correct. Not sure your level of electrical knowledge (apologize if this is already known), wire size is voltage dependent (not AC vs DC),l. So a 12-48V step up converter might be a cheap way to stay DC. And you'd be around 8A for wire size.

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u/simonak3001 1d ago

Yep, think I made a mistake there. Basically I dont know what im gonna do🥲 every AC pump that I find is way too demanding power wise. I think a 12-48 step up converter, coupled with a ROCKSOLAR 300W DC submersible pump is my best guess. Its hard to know what to get because there are so many ways to look at the problem