sump pump siphon

The sump pump in my basement is on the high side of house, meaning that the ground on that side of the house doesn't slope away from the house very much. As a result, there is about 40' of hose on the outside of the house to get the water far enough away to flow away well, and I am tired of moving it to mow.

I'd like to run the sump pump discharge in the floor joist cavity and have it come out on the other side of the house, where the ground slopes down sharply and there is already a buried 6" pipe for the gutter that takes it's discharge out 60' or so from the house.

For the sump pump that means a 2" pipe going through a check valve, up 8', then across a room 16' before it would exit the house. Sump pump discharge is kind of a weird deal in that the vertical part of the pipe will stay full but I want the horizontal part to drain, and drain quickly, so that the part poking out from the house doesn't have a chance to freeze. I think that means I should have a siphon break to get air in at the elbow so the horizontal leg drains.

So, I have a 2" elbow that has a 1/2" fitting in the corner designed especially for a siphon break. Assuming a install the elbow and run the horizontal leg of pipe out the other side of the house, where should I run the 1/2" air inlet line?

I think I have 3 options:

Run a short chunk out the existing hole to the outside and maybe put an elbow on it to keep stuff out. This would be easy, but with a strong wind blowing against one side of the house would there be a chance of cold air going through the line?

I could turn the 1/2 line and run it back to the sump. This has the advantage of diverting any water that might come out the vent while the pump is running back into the sump, but it might not vent as well.

Or, I could run the 1/2" line across the room too and have it come out next to the 2" discharge. I'm leaning this way, but am I over thinking it?

Im not sure why you want to run tubing from the elbow.

I would install the elbow with the 1/2" port pointed up and then use a vacuum relief fitting:

Vacuum relief valve

I'm not sure how well those will hold up to actual pressure in the pipe if something happens and the pump is running, and I don't want one of those in the ceiling when I finish the basement.

you have a vertical drain vent anywhere close? pipe it to that...

If it was a vacuum break for a drain application (like a dishwasher), I would have similar concerns.

I'd be more confident in something like this Since this is intended for use on a water supply line with an intended application of a water heater, where there is always pressure and a failure could result in flooding of a property. The specified working pressures are up to 200 psi so the sump pump shouldn't come close to the operating limits.

Based on the requirement for 1/2" vacuum to open the valve to let in air, the vent is normally closed and doesn't rely on pressure in the pipe to close it, so there should be any dribbling when the pump cycles.

One option would be to run the 1/2" line to a safe location and then install a vacuum relief valve to minimize the risk of damage while still avoiding the potential to have your vent line freeze.

It'll slowly drain out. I wouldn't worry about it and I didn't. I sent my sump pump out the opposite side of my house from the pit location. It runs about 10' in the air under my porch, then a sanitary tee down (and a cleanout on top) to below grade. If you keep it pitched it'll be fine. We regularly get -20°F and I've hadn't had a problem yet and don't expect one.

The ground water here is about 45-55°F or so and it would have to be a pretty crazy cold and windy to freeze water in the short amount of time it's exposed. Just don't use corrugated pipe above ground, that can hold water indefinitely and freeze.

Is this some super badass 240 volt sump pump that will actually fill a 2" drain line? Ill hazard a guess that during pumping the pipe will be more like half water, half air, so it should never vacuum lock to begin with.

Friend has this on his house. Sump pump on the high side, plumbed up and over to the other side of the house.

He has no check valve, and no problems with the bit of water that sloshes back down into the sump when the pump turns off. It's not enough to restart the pump. It's just an open pipe and works just fine.

I'm with Foxtrapper. My pump goes straight up ~8' to a 90 and then 4' to the wall and another 4' before ending. I made sure that the horizontal part of the pipe slopes downward so it drains outside. No check valve anywhere, the water that drains back on pump shut down only raises the level in the sump ~1/2". System has been working like that for 20 years with no problems.

My sump pump specifically requires a check valve to keep the impeller from spinning backwards when the water drains, so it's got to be there. There is a school of thought for drilling a small drain hole in the pipe above the check valve to let the line drain; I could go with that too.

When the pump is running it really moves water. The sump pit holds 10-12 gal of water and the pump typically only runs about 20 seconds pumping it out.

Could you run a line from your 1/2 inch hole back into the pit?

You are over thinking it.

Install the "horizontal" pipe with a pitch to it. It will always drain. 16' horizontal is really short. It will drain quickly with no assistance.

There isn't any pressure in the pipe. It's open at one end.

There is 8' of head pressure sitting against the check valve. That's all.

What about increasing the pipe to a 3" diameter after the elbow?

That should ensure it flows more in the horizontal section than the vertical and doesn't fill completely. The larger diameter pipe will act as a wet vent and allow it to drain quickly without any extra venting.

Drill a hole just above the check valve. And if you want a vacuum break you can use another check valve at the high point. When there is pressure in the line it stays closed and as soon as the pump shuts off it falls open. And if you are worried about it leaking connect a small diameter hose to it and run it somewhere.

oldopelguy wrote: My sump pump specifically requires a check valve to keep the impeller from spinning backwards when the water drains, so it's got to be there.

And how would spinning the pump backwards a wee bit hurt the pump or the motor?

Not that I really think the slight weight of the column of water will really push the pump backwards. It's far more likely to simply leak around the edges of the impeller.

7 foot column of water is 3 psi. Not exactly high pressure.

In reply to foxtrapper:

I think running the pump backwards would be a disaster.

It would suck air through the discharge and pump into the sump pit. It would make a mess, but the bigger issue is the water level would never drop. The float switch would never turn off, which means the pump will run dry continuously.

Plus, the building will flood.

Don't put any kind of vacuum breaker or vent on the discharge pipe. You are asking for disaster. The pressure and velocity of the discharge water is substantial. Plumb the discharge as high up into the bay as possible and then pitch in downward to the point of discharge. Standard pitch for a 2" pipe is 1/4" per foot, so over a 16' run, the top of the pipe should end up 4" down from the floor above. Make sure there is a check valve at the pump or it will short cycle and burn out the pump. Make sure you use pressure fittings and not the short socketed regular PVC drainage fittings. Install lots of supports for the horizontal pipe... at least one every 24". 2X4s between the joists work great. Rubber fernco couplings at the check valve help reduce the noise. Upsizing the horizontal pipe is a good idea. If you do that, then you can use regular fitting across the ceiling.