How to pipe two pumps into the same sump pit?

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Old 07-17-17, 10:24 AM
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How to pipe two pumps into the same sump pit?

The attached photo is of a 500 gallon drainage tank which is at the low spot of my property. It fills with groundwater and then gets pumped as the water level rises. I have one large Zoeller pump (on the left in the photos) that does all the work. My goal is to have a second, smaller backup pump at a slightly higher level in the tank (the one on the right) which will have its own float switch that activates if the main pump ever fails.

The black ABS pipe in the photo was my idea on how to hook up the two pumps and feed into the same 100' buried pipe that leaves the tank. The configuration of piping in the photo isn't working as I had hoped.

What currently happens when the main pump is running is to have part of its water come right back down into the black ABS pipe and go right back into the tank through the bottom of the backup pump.

I was surprised that the main pump didn't force all its water straight up and out of the tank.

What would I need to change with the arrangement of pipe fittings to make sure each pump would have all its water exit the tank and not feed back into the other pump's piping? Ideally, I would like to have two complete lines but its 100' of buried piping once it leaves the tank so I need to figure out how to configure the pipes in the tank to work with one or the other pump and not feed back.

Thanks for any ideas.
 
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Last edited by fromhollywood; 07-17-17 at 11:48 AM.
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Old 07-17-17, 12:30 PM
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You need to have a check valve just above each pump and before the Y.

To get the room you need.... the Y will probably need to be in the horizontal run.
 
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Old 07-17-17, 01:07 PM
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Thanks for the idea of the check valve. You can see I have a brass one in the photo but I had to remove that. The problem I had with using any check valve is that the 100' of mostly horizontal buried PVC freezes if water remains in it as it would with a check valve

By removing that check valve, the remaining water left in the 100' of pipe falls back into the tank after the pump stops running. That keeps the buried pipe clear so it won't freeze. That pipe clearly should have been buried below the frost line and more of a downhill slope but it was installed by a prior owner and would be a big job to dig and replace.

Without a check valve, I get about a gallon or two of water that falls back into the tank after the pump stops running and that is an acceptable trade off and prevents the line from freezing.

Check valves are a great idea but I don't know a way I could use them in this installation.
 

Last edited by fromhollywood; 07-17-17 at 01:24 PM.
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Old 07-17-17, 03:33 PM
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The only way to isolate the pumps is with two check valves. You need some type of vacuum break to allow air into the horizontal drain line when the pumps aren't running.

Possibly an air admittance valve.
Does the water in your pit freeze in the winter ? An AAV may possibly freeze too.

Maybe Dane has an idea. He'll be by later.
 
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Old 07-17-17, 03:52 PM
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No, the water inside the tank never freezes as it fills pretty quickly during rainy seasons and its over 4 feet deep. When I had that check valve you see in the photo, trapped water did freeze inside the buried PVC line a short distance from the tank. The 100' of PVC is probably just eight inches under the ground and should have been buried much deeper to avoid frost.

If I put the wye along the horizontal section of PVC inside the tank, would that prevent one pump's water from entering the other part of the wye? As it is, I have the wye in the vertical section. My guess is that wye will always let water from one pump turn into the other part of the wye.

Another idea: Is it possible that there is a different type of wye that would make it impossible for one pump's water for make the turn as its doing with this wye?

Thanks. I will look into air admittance valves. I don't understand just now though how an AAV would prevent water from getting trapped in the buried part of the PVC in the yard which would happen if I had check valves. An AAV would prevent a vacuum but I think the water would still be trapped because of the check valves.
 
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Old 07-17-17, 09:24 PM
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Take out the check valve you have in there. Install a Tee with an AAV on top.
The AAV will close when pumping. It will open to allow air in when pumps stop.
 
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Old 07-17-17, 11:51 PM
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Thanks very much for the idea of the tee and AAV. I will reconfigure the piping with two check valves (one at each pump) and the tee and AAV in the horizontal position right before the piping leaves the tank. I will report back on how it works.

Thanks!
 
 

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