Dual sump pumps-check valve?

[Joe J]

In the same crock I have two sump pumps on two separate breakers. The primary pump has a check valve installed and it drains into a underground pipe that runs to a sewer. The backup pump float is set a little higher and turns on if the primary doesn't. One and a half inch pvc pipe that rises about 8 ft and does a 90 degree turn before heading outside and draining onto the lawn and it has no check valve.

So here are the questions...Is there a valid reason for not having a check valve on the backup? I had a failure on the primary pump and it seemed half the crock was refilled by the remnants in the pipe draining back after the backup pump shut off.

Is there a standard height a check valve should be installed and wouldn't it make sense to install one on the backup pump?

This was the arrangement when we bought the house in March and I only noticed this after the primary failed. Actually, the pump didn't fail, the float switch did. $30 for a replacement.

[Andy]

Andy comments:

I would think that if the water level get high enough to fill the second pump (as a result of the higher float switch), that a check valve wouldn't be necessary..... ` The check balve is merely to keep the pump primed, and if the pump is flooded, a check shouldn't be necessary unless it clicks on before the water level is high enough...... HOWEVER, that being said, what is the nature of the second sump pump.?? Is it a submersible, or is it a pump that is mounted above the water level ?? That would be a problem.... and I would use a check valve....

I will read with interest the advice given here by others. Lots of good info to be gleanded from this group...

Andy in Eureka, Texas P.E.

[Joe J]

Both pumps are submersible, only difference is where float turn on point is set on each.

[trader4]

One reason I can think of is to save a few $$, because the backup will rarely, if ever, be used. And the only downside to not having a check valve is that some water will run back in. For an installation where the pump only runs occasionally, it's a backup, etc and not that much water runs back in, it's not an issue.

Other reason would be if water that would be held in place by a check valve is subject to freezing. Then it would be relying on water being able to drain back to prevent freezing.

=A0I had a failure on the primary pump and it seemed half

How much water runs back in is determined by how much pipe there is that is left filled with water when the pump shuts off. In your case it sounds like it's substantial amount.

The closer it is to the pump the less water will flow back. Height isn't an issue. Usually it's put above the sump pit for convenience. If a lot of water flows back, then yes it would make sense to put one in to keep the pump from going on and off more frequently.

[trader4]

Sump pumps are all self-priming out of necessity. And a check valve will not keep it primed anyway. The water between the pump and the valve drains back into the sump pit. The valve is there to keept the rest of the water, which could be substantial depending on how the piping is run, from draining back into the pit. If it does, the pump is just re-pumping that same amount of water that drains back each cycle.

and if the pump

How many sump pumps have you seen that are mounted above the water level? Every single one I've ever seen sits in the sump pump pit, in the water.

That would be a problem....

, Texas =A0 P.E.- Hide quoted text -

[Andy]

Andy replies: None. But , based on the post, I wasn't sure the OP was referring to a "sump pump", or a "pump that was used to pump out a sump".

People in different areas sometimes have different terminologies..

JoeJ replied that they were both submersible, hence, I can't see why a check valve would be needed for either....

I agree with your post...but I can't see why you replied to "me" rather than Joe J...

Andy in Eureka, Texas PE

[Andy]

Andy answers: A question of terminology..... Both do the same thing --- a valve that allows matter to flow in one direction. In my experience, a "foot" valve is often mated with a screen and a "check" valve is simply inserted in-line... If JoeJ's pumps are both submersible, I can't see where either could be used..... Perhaps I am missing something, since the submersibles I have used don't have a convenient place to add either one......

I'd be happy to get information on my error.....

Andy in Eureka, Texas PE

[Joe J]

Still trying to stay on topic. Both are submersible, primary has a check valve that prevents the water from draining back into the crock. Backup has no check valve and has at least 12 feet of 1.5" PVC before it reaches outside. When that pump turns off, the contents of that 1.5" pipe drain back into the crock and almost refill it. Yes it is just a backup and in theory only runs if the primary fails, but in this case the primary did fail and it didn't seem very economical to have it pumping the same water twice. So, spend X dollars and install a check valve? I'll do it myself.

[don &/or Lucille]

[Tony Hwang]

Hi, Our house does not have water problem but I installed check valve in the main sewer line. It is good safety feature. Very unlikely but worst case your two pump can fight each other.

[Vic Smith]

Put a check valve on it. Cheap and easy. I have 2 pumps and put a check valve on each.

--Vic

[Andy]

Andy comments:

Joe, I'm sorry, but I really don't understand.. If both pumps are submersible, --- by that I mean the type that, when operational, is partially submerged in the sump, I don't see the need for a check valve in either.... As long as the float switches are above the pump levels, the pump will be flooded.. and primed.... Water flowing back down a discharge pipe will flow out to the ambient water level, which, if the pump is still submerged, shouldn't matter.....

However, if your "primary" pump didn't work, you should get it fixed.... As a suggestion, the problem may actually be in the float switch (sold at Home Depot as a separate item for about $30 USD).. and is easy to replace..... generally.... The float switch fails more than the pump does, in my experience....... which may not be as great on this issue as other posters..

I like the idea of a backup..... especially if a small flood will cause you serious difficulty or loss... But I'd have both systems working ..... That's just me, tho....And I really like the "separate breaker" approach...

Andy in Eureka, Texas

[Art Todesco]

I've always had check valves on both pumps in my old house for some 37 years. Both pumps were submersible and one was battery operated. The only problem I had was with the battery pump. Sometimes, the head of water would keep the battery pump from actually pumping, even though it was running. The instructions on the Basement Watchdog battery pump say to drill a small hole in the pipe just above where it connects to the pump. I did it, and it worked. The best sump system is what I have now ... gravity. All perimeter tiles are just going to the side of the mountain. If, for some reason, water should get in the basement (a walk out on one side) just open the door.

[Joe J]

Maybe I'm not being clear. I replaced the float on the primary and I'm back to having two operational pumps. A primary and a backup that kicks in if the primary should fail. Both are submersible. If the primary fails and the secondary needs to run, the water in the pipe seems to drain back down and refill a portion of the crock because there is no check valve to prevent the water from draining back down. My original question was if there was a valid reason for not having a check-valve in that pipe. From the answers, it doesn't appear to be any reason to not have one and I can buy one for $10 and install it myself.

[Vic Smith]

Think he said they are on separate discharge lines, so they won't fight. The check valve will prevent pumping the same water twice.

When I added the second pump to my pit with a Y I brain-farted with the check valves and had to redo it. One pump would backfeed through the other. Putting a check valve over each pump discharge fixed it.

--Vic

[Joe J]

Yes, two separate lines. One underground to the sewer, the other, out of the side of the house and on the lawn.

[trader4]

.

That's a good point. If Joe adds a check valve, he should put a small hole in the pipe too. Without a check valve, as water rises in the pit, it will naturally rise inside the discharge line as well, pushing air slowly out the discharge line. With a check valve, the air is blocked, so you could have the portion of the discharge line from the check valve down to the pump itself filled with air. When the pump starts, it's possible the line will remain air-locked. With the tiny hole the discharge line will have water in it to the same level as the pit.

[trader4]

"Dual sump pumps - check valve?

In the same crock I have two sump pumps on two separate breakers. "

It's one of the clearest posts I've seen.

" I had a failure on the primary pump and it seemed half the crock was refilled by the remnants in the pipe draining back after the backup pump shut off. "

That's why.

To correct the misinformation.

, Texas =A0 =A0PE

[Colbyt]

Andy

The only purpose of a check valve on a submersible pump is to prevent the backflow which can cause the pump to cycle repeatedly.

The water in the pipe refills the basin prematurely. The pump kicks on, shuts off and the whole process repeats again. Over time this can cause premature pump failure. I once watched one with a small basin pump the same water every 2 minutes. I added a check valve that very day.

For Joe: Add a check valve. Be sure to read the instructions. You need to drill a 1/4" hole in the pipe near where it connects to the pump to allow the water between the pump and the valve to drain.

[Ed Pawlowski]

The three we have for a pit at work? They are actually part of a water system and pump the water from a pit to a cooling tower and are mounted at ground level. Thus the need for a foot valve. They draw from a pit that is about 5' deep and pump to the tower that sits about

20' above ground level outside the building.

OTOH, you are correct about the typical sump pump application used in basements. They are best right inside the pit and operated with a float switch.

We do have a sump pump that has a check valve in line. The check is needed because it is connected to a common line that other pumps are connected to that go to the sewer. This is more in line with the setup the OP is talking about. With no check valve, water will go back to the other pump in line. IMO, the OP needs a check valve in line after the pump.