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I have a cabin on stilts in Maine where the frost line is 4ft deep. I’m looking to make a system to supply water to the house that I could use in the winter. Seeing as the cabin will not stay above freezing when I’m not around (and possibly even at night when I am around from time to time if it’s really cold), I’d like to design a very simple drainback system that would allow me to drain back the house to below the frost line.

Recently I learned about freeze-free hydrants and figured I could plumb one of those into the cabin and just open it when I need to use water and close it when I don’t but I’d prefer if they make a similar system that can be controlled off a switch or a less intrusive mechanism than the big lever (just for aesthetic purposes seeing as it will be indoors).

Does anyone know about such product or what it would be called?

Also any further advice on how to design the plumbing such that it will easily and freely drain out would be very much appreciated!

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    Will need more information on how you get water to the cabin. To drain have all pipes slope up/no horizontal level pipes, turn off water, open all faucets and open up drain. Water likes to flow down by itself
    – crip659
    Dec 4, 2023 at 13:36
  • Related: diy.stackexchange.com/questions/186576/…
    – isherwood
    Dec 4, 2023 at 15:26
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    Dec 4, 2023 at 15:27

1 Answer 1

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The basic foundation of an easily drained water supply system is to build it on the same principles that a waste-water system follows - every pipe, consistently and without fail slopes to the drain location. It may be beneficial to add a few vacuum relief valves (sold for a code requirement on water heaters, typically) to vent the pipes when draining.

Though, in the age of PEX, a common enough approach is to worry less about the pipes freezing, if they are PEX.

Standard approach for a location with power is to insulate the pipe well and install electric heating for the pipes. The cheap junk with a separate thermostat is what's usually on offer at the hardware store, and fails a lot. The better version self-regulates on the outside of the pipe. The best version of those goes inside the pipe. The first-time cost runs as expected (increasing) from worst to best. The longer term cost runs as expected (decreasing) from worst to best. Cheap is expensive in the long run.

If you wanted to use a frost-free hydrant as your feed, you'd probably want a hose quick-connect on it, with a short hose connecting to the plumbing, and all the plumbing sloped to the that point. Disconnect the hose and drain the pipes into a bucket, while the hydrant drains into the ground below.

You could cobble up something to mimic the operation of a frost-free hydrant with a below-frost-line electrically operated 3-way valve, and at least one check valve (on the drain port, to prevent things from contaminating the supply through the drain port.) You might have a have a fun time digging it up when the mice/voles/moles/shrews chew the wires for you in mid-winter. I'd choose a big lever and a rod , (quite similar to the FFH handle) and a manually operated 3-way down the hole; the handle could be concealed in a wall cupboard somewhere (or be outside the cabin) if you find it visually jarring. Or perhaps use a set of moose antlers on the wall that you rotate as the lever.

Draining the entirety of the cabin plumbing there will either be no problem if the percolation is good, (typical of gravel) or a big problem if the percolation is not so good (typical of clay soil.) The frost-free hydrant approach you're only draining the riser tube, which is quite a bit less water. Perhaps bury a perforated drain pipe leading away from the valve box while you're digging to take the drainage water and give it space to percolate from without backing up the pipe.

If there's a water heater in this cabin the drain volume gets potentially much larger, (I suppose it might be a propane tankless and not much volume) and you have to ensure that the heater never turns on when it's not full of water.

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    +1 for secret handle moose antlers!
    – FreeMan
    Dec 4, 2023 at 17:22
  • When outfitting a cabin, a good question to ask is Would this potentially attract Agent 99...?
    – Ecnerwal
    Dec 4, 2023 at 18:04
  • If there's a flush toilet you're going to have a challenge draining the tank and trap. In fact, you will have to deal with all the p-traps in the house. Draining them leaves you vulnerable to sewer gases backing up into the house. You're better off just dumping some non-toxic anti-freeze in the traps each time you leave the house, assuming it's compatible with your septic system or allowed if you're connected to a community sewer line.
    – Llaves
    Dec 5, 2023 at 4:23
  • @Llaves this question is about the supply system. The drain system is a different question, and an issue that anyone with a seasonal cabin with plumbing already deals with every year, unless they waste lot of money heating it when they are not there.
    – Ecnerwal
    Dec 5, 2023 at 14:07
  • @Ecnerwal - the toilet tank is on the supply side and will not drain down. And I apologize for trying to be helpful by reminding the OP that he has to deal with the traps which will not drain.
    – Llaves
    Dec 6, 2023 at 15:43

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