I have cistern which is filled either by truck or pumped from the lake. To connect to the cabin, there is a pipe with a foot valve at the bottom, and a pump with a pressure tank at the bottom of the cabin.
My setup is a bit different since we don't have a basement, and the pump is closer to ground level so there is around a 5 foot (1.5 m) height difference between the foot valve/bottom of the cistern to the pump.
In the current setup the foot valve works perfectly, you prime the pump at the start of the season, and it doesn't lose prime. I want a valve which at I can open without going into the cistern to drain the water at the end of the season.
The problem that I am trying to solve is during winterization of the cabin. We can drain all the lines inside using compressed air, but to drain the suction line (from the pump to the foot valve), we remove the foot valve so it all drains. Is there a better way of doing this?
I looked up how it's done with submersible pumps, and it appears that there is a snifter valve paired with a drain back vavle (also called water outlet, "bleeder valve" or "Bleeder Orifice". There are two versions:
Copper (with a ball):
As a pump turns on and builds water pressure, the orifice is forced closed with a ball. When the pump shuts off, pressure drops and the orifice is opened, allowing water above the orifice to drain out.
There is also a rubber version:
Provides fast water bleed capacity through its large orifice opening when pump shuts off Orifice completely closes when the pump is running and prevents loss of pumping volume
How do these work and would they work in my case?
From the sub pump version, I believe they need a Snifter Valve which allows air into the line.
My understanding, in theory in my case, if my plumbing is air tight, when the water pump stops and the tank is pressurized, not much water would drain back out of the drain back valve.
In practice, when I installed the foot valve with a small gap (I didn't warm the pipe up before putting in the barb), it was leaking and the pump would lose prime every 3 minutes (since air might be entering from a joint in the buried pipe?). I'm afraid if I installed this drain back valve, I would have the same problem potentially as I might have an air leak somewhere.
Are there other alternatives? One idea is a pressure blow off valve right after the foot valve. This way I could add a string line and pull it open to drain.
The other ideas I have seen is connecting a fishing wire to the foot valve so you can pull it open from outside but it seems sketchy. This is explained in this video: https://www.youtube.com/watch?v=PGV0BSPDPbQ but the idea is he glues the foot valve nut to a washer with a hole which is connected to a fishing line:
The other idea is a ball valve which is spring return ball valve which is normally closed and doesn't have a too tight spring. This also seems unideal as it will be submerged.