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.
it all depends on the size of the 'crock' as you call it. If the sump is of sufficient size, then you can get away without a check. But having said that, it is standard procedure to put a check on the pump down low. (like screwed into the pump, then the discharge pipe connnects to it.)
the check VALVE is NOT there to keep the pump primed in the case of a sump pump.
it is installed on the discharge side to prevent the contents of the riser pipe from dumping back into the sump. And no, a foot valve is not the same as a checkvalve on the discharge side. A foot valve is used on the suction side and IS in fact there to keep the pump primed, in the case of a well pump (or any other pump for that matter) that is above the water line.
yes, $4 or $5 well spent especially if you have a small sump.
the 1/4" hole is a wives tale. Not necessary.
it's necessary for the same reason it would be necessary if it was the ONLY pump he had.
bs. where does this alleged "air" come from?
ACTUALLY, the are usually threaded and screwed directly into the pump. Then the pvc attached to the checkvalve.
here's what you are looking for:
Exactly the type of valve I was talking about installing. $9 at Home Depot. After sorting through all the responses, I think I'll just go ahead and cut the pvc pipe on the backup and install one.
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.
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.
y in Eureka, Texas
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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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You claim it's BS, yet others have given cites here back to sump pump manufacturers that call for putting that small hole in the discharge line. I just installed one last week that also called for the hole in the instructions.
As I already explained, the air in the pipe comes from the water between the check valve and the sump pit water level draining back into the sump when the pump shuts off. The check valve only prevents the water in the rest of the discharge line from flowing back.
So now you have a section of pipe full of air. Worst case, if the basin is dry, there is no water at all and it's initially all air in the pump and pipe. As the sump basin fills, without a check valve that air would be displaced and the pump and pipe would fill with water too. The water level inside and outside the discharge line would be equal. With the check valve, that air remains trapped and it can stay there, air locking the pump. Meaning the pump impeller remains mostly or entirely surrounded by air, unable to move water.
That is the purpose for drilling a small hole in the discharge line near where it connects with the pump. With the hole, the water level inside the pump and pipe will be equal to the water level outside. And that way you are sure that the pump cannot airlock.
Exactly and I figured that is what we are talking about since it's a home repair group and nothing indicated there was anything exceptional about the situation. And everything since then shows that was correct.
I'd probably put one in too. I would definitely put one in if it were the main pump. Being a backup, the fact that some of the water will flow back in isn't as much of an issue because it's not going to be happening frequently, only if the main pump fails. So, if the pump cycles a bit more, it's not a big deal.
I thought this was BS too until I read up on it. What you say all makes sense. So I won't argue against the pump experts, just make a few comments. If a pump is primed, there is no air at the impeller. If the sump is dry the pump isn't primed and there's air around the impeller.
Where does the air come from? All the water has drained out, simple as that. The water between the pump and the check valve gurgles down, so the pump is full of air. As the sump fills, the pump head fills with water, priming it. Air in the discharge line can stop the water from filling the pump head if the air compresses because it can't escape. Then you have pump airlock if the pump goes on.
Here's where it gets a little tricky, and what fooled me. How much head pressure does it take to overcome the air blockage? I've got 2 pumps with check valves and no drilled relief holes. Pumps always work fine. Now some pumps have that relief hole built into the head. I don't know if mine do or not.
The check valves I put in have light rubber flaps. Wouldn't take much pressure on the underside to unseat them. Then the pump head will prime. Back to head pressure. Some pumps kick on before there's much head pressure, others wait until there's more water in the sump. A float switch can be set to adjust that. Both of my pumps have diaphragm switches with no adjustment. I've noticed they don't go on until almost the entire pump is covered with water.
Anyway, though my pumps aren't getting airlocked, what if the rubber on the check valve take a real good seat, and sticks a bit? I could get airlock. So when I get around to it I'm going to drill the relief holes.
--Vic
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And why would it "air lock" even without the hole? The pump is going to push water up the pipe, compress the air which will push open the checkvalve, push on he water above the checkvalve and the entire system works just as it would as if there were no air in the system. As long as the check is above the pump rotor it cannot air lock.
Harry K
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Ah! The light dawns. You are correct. If the sump ever drys below the impellor level it could air lock.
I also drill the holes when the manual calls for it.
Harry K
no one mentioned the obvious, sump pumps should never drain to a sewer. in heavy rains it can cause flooding not only of your basement but the sewer lines in the neighborhood and sewer plant..... too many such connections..... equals flood:(
having seen first hand sewer water gushing up out of a basement floor drain its no fun....
if the sump pumps check valve sticks open under heavy rain the sewer crud could fill and contaminate your interior french drain:( might require digging it up to replace it:(
everyone with a sump pump should check to see if theres ANY WAY to drain the sump to daylight! far too many people want to avoid digging and install a pump when just a drain line would work fine
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