Dual sump pumps-check valve?

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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.
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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.
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wrote:

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

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wrote:

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
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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.
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wrote:

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

dont use a check valve if the line is exposed to freezing temperatures. the original homeowner may have intentially set it up to drain the water back to the sump to prevent a frozen line
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On 11/21/2011 9:03 PM, bob haller wrote:

That's kind of a given, the pumps I've installed have a slope on the output line after the check valve which I install in an area that's less likely to freeze. I'm in the Southeast and temps don't usually fall so low that basement temps get down to freezing. If I was in the North, I'm sure I'd have to be more cautious installing any sort of drain line. We Southerners are sissies when it comes to cold weather. I worked out in the Pacific for a year close to The Equator so I lived and worked in shorts and a T shirt every day. When I came back to The States I landed in Southern California during a cold snap where temps fell into the 60's and I was freezing. ^_^
TDD
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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
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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.
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Several commenters don't have a clue. Yes, you should put a check valve in the backup system since there is a lot of water stored in the vertical pipe above the pump that you don't want to have running back into the sump, when the pump is called upon in a failure of the first pump. IT has nothing to do with priming or foot valves or anything except what you originally surmised. The horizontal output pipe should be sloped downward going out so that all water in the horizontal pipe does drain out after the pump stops, especially if you are in an area with freezing temperatures.
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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.
--
Colbyt
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On 11/20/2011 8:36 AM, Colbyt wrote:

the 1/4" hole is a wives tale. Not necessary.
--
Steve Barker
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As Steve B stated, that 1/4" is unnecessary. It's not like the internals of the pump will prevent that bit of water between the pump and the check valve. Drilling a hole in that location will allow a small amount of the pumped water to "short circuit" and merely recycle in the sump, wasting a bit of the pump's usable output.
General comment to group (not to Steve B):
I thought the "well" in which water collected was the "sump" and the pump tasked with emptying the sump was the "sump pump"?
What is this "crock thing" being talked about? I thought crocks were for sauerkraut, sourdough starter, pickles, cheese, yogurt, etc and of course s...t.
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It may not be necessary. But one thing I always do the first time I install something is RTFM. Or at least look at the pictures.
Both the pump and the valve maker recommend the hole. I never throw anything anyway so I have the printed instructions somewhere.
The Ace website indicates that their pump have a built in vent hole so it may not be necessary for their product. Older pumps may not have the built in hole. If you don't know for sure the small hole hurts nothing. http://www.waterace.com/pdf/R3S%20R3V%20R5S-1%20and%20R2SA%20Sump%20Pumps%20Manual.pdf
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On Sun, 20 Nov 2011 08:03:26 -0800 (PST), Andy

I think you are right for the wrong reason. The two pumps discharge to separate lines so no check valve is needed. If the pumps went to a common line, the check valve would be needed to prevent backflow into the other line and back to the crock.
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On 11/20/2011 9:49 AM, Ed Pawlowski wrote:

it's necessary for the same reason it would be necessary if it was the ONLY pump he had.
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Steve Barker
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On 11/20/2011 10:43 AM, Joe J wrote:

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.
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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.
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