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 Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

The sump pump that came with my new home failed after 10 years. I thought it would be an easy thing to replace - apparently not. I have bought two new pumps because I thought the first one I bought was faulty but I have the same problem with the second.

The original sump pump did not have a check valve and never got air locked. It ran problem-free. The new pump gets air locked all the time. I have tried installing a check valve in the pit above the pump and when that didn't work I tried installing a valve where the pump rises up the basement wall to exit the house. I have also tried drilling a hole in the pipe in the pit. Nothing works.

I am thinking that the design of the discharge pipe contributes to the problem because it seems to me that it has a built in air trap. The pipe comes out of the pit, rises about 6 inches above the basement floor, and then runs horizontal for about a foot. The pipe then runs back down through the basement floor and runs under the concrete slab all the way to the other side of the basement where it rises out of the floor, runs up the wall and out of the house. Water probably gets trapped in the pipe under the slab and there is air trapped in that horizontal one foot long part above the sump pit.

Any ideas as to what the problem is and what I need to do?

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 Re: Replaced Sump pump - now have air lock problem
Author: jerco (MD)

Sounds like the discharge line is clogged up.

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 Re: Replaced Sump pump - now have air lock problem
Author: packy (MA)

drill a 3/16 hole in the pipe below the check valve. drill the hole at an angle upwards so the water will spray downwards.




Edited 1 times.

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 Re: Replaced Sump pump - now have air lock problem
Author: LemonPlumber (FL)

think Packy has you covered.

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

Thanks for the responses. I don't think the discharge line is blocked as it works fine once I get the air out of the system (until) the next time).

I don't currently have a check valve as the old sump pump worked fine without one. I did try putting one in though and I did drill a hole below as you suggest. It didn't help - so I took the check valve (and hole) out.

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 Re: Replaced Sump pump - now have air lock problem
Author: LemonPlumber (FL)

Doug is this pit sealed?Is it vented after the cover goes on?

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

The pit used to be sealed but I damaged the cover when I replaced the original pump (had to cut it off) so it is no longer sealed. Would it make a difference in the operation of the pump if the pit were sealed?

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 Re: Replaced Sump pump - now have air lock problem
Author: SMSPlumbing (PA)

It sounds to me that something is in your discharge line. Your other pump did not have a check valve because the way you explained the pipe sounds like it makes a trap. I would snake the line out regardless you may think it is fine. I would still leave the hole in the pipe whether you have the check valve or not.

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 Re: Replaced Sump pump - now have air lock problem
Author: hj (AZ)

An "air trap" ONLY occurs inside the pump, and a properly drilled hole in the riser pipe eliminates that. You have a completely different problem, but it is NOT an air lock, from what you have described and what you say you have done already.

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 Re: Replaced Sump pump - now have air lock problem
Author: hj (AZ)

HOW do you get the air out "until the next time"?

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

To remove the original pump after it failed, I had to cut the discharge line and I did that at that one foot horizontal area above the pit. When I installed the new pump I used one of those rubber connectors with the two hose clamps. To get the air out, when the pump is running I loosen off one of the clamps and air comes rushing out. When it starts to spit out water I unplug the pump and tighten the clamp. When I unplug the pump you can hear water falling back down into the pit.

I then plug the pump back in and it usually works. Sometimes though I need to do this a couple of times.

It is like there is water in the pipe under the slab and air in the pipe in the horizontal part above the slab - and in order to actually pump out water that air as to be removed. That horizontal part works just like a trap under a sink only it traps air (because it is like an "N" instead of a "U";) instead of water like a sink trap.

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 Re: Replaced Sump pump - now have air lock problem
Author: SMSPlumbing (PA)

Is there a reason you have to keep the same pipe set up? Can you go straight above the pit then out?

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

I would like to keep the same setup if possible as my basement is finished as living space and it would require extensive renovation to change the location of the discharge pipe.

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 Re: Replaced Sump pump - now have air lock problem
Author: treeman8 (MI)

Could the current system have a huge amount of head pressure with the water sitting in the pipe under the slab?

Did the old pump have some design that had a check valve right at the pump so that little or no air ever entered the pump? EDIT TO READ "no air entered the LINE (not pump)"

Could a few feet of air in the line near the pump be enough of a compressive cushion so that the pump cannot overcome the large head pressure?

Is your new pump maybe too wimpy or of a different design to overcome the hypothetical head pressure?

Just some guesses on an intriguing problem.



Edited 2 times.

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 Re: Replaced Sump pump - now have air lock problem
Author: hj (AZ)

The pump creates "pressure" which will push any air out of the line. It is more likely that you are venting the air from the pump so it CAN create the pressure.

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

>>Is your new pump maybe too wimpy or of a different design to overcome the hypothetical head >>pressure?


No. The old sump pump was a 1/4 HP and the one I am currently using is of the same design and 1/2 HP. I had also tried one of a different design and 3/4 HP.

>>The pump creates "pressure" which will push any air out of the line. It is more likely that you >>are venting the air from the pump so it CAN create the pressure.

How does this air get in the pump? How would I prevent this?

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 Re: Replaced Sump pump - now have air lock problem
Author: LemonPlumber (FL)

If you drilled a hole just above the water level at activation it should have worked as said.check /trap or none.

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

I will try that again. Perhaps when I drilled a hole before it was too high or too low...

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 Re: Replaced Sump pump - now have air lock problem
Author: LemonPlumber (FL)

It needs only be above the water line when the pump starts.drilling upward so it sprays downward is smart.but the hole lets air out and will also spray out water when the pump is pumping water.

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 Re: Replaced Sump pump - now have air lock problem
Author: hj (AZ)

ONe way is if the pump does not turn off when all the water is out of the pit. In fact, it is about the only way it can happen.

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

The hole has been drilled. I will monitor the situation and report back. Thanks for all your help.

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 Re: Replaced Sump pump - now have air lock problem
Author: hj (AZ)

IF it works, then find out WHY it was getting air into the pump, because that only happens when there is a malfunction of the float.

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

So far I am still having the problem. The only difference now is that water shoots out of the hole (at great pressure) but still doesn't go up and out the discharge pipe until I unplug the power cord a couple of times. When I do that there is some gurgling in the pipe and when I plug the cord back in - it will discharge.

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 Re: Replaced Sump pump - now have air lock problem
Author: hj (AZ)

YOu have a problem which may be impossible to diagnose without being there. IF water is coming out of the hole then the pump is creating pressure, and as long as there is pressure, ANYTHING in the pipe should be pushed out, and if cannot be pushed out, the water should not flow no matter how many times you plug the pump in.

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 Re: Replaced Sump pump - now have air lock problem
Author: LemonPlumber (FL)

Are yous sure it would not empty the pit in time or have you set the amount of time by the running time?The top third of the lift station may take longer with some activation set up,s?Is the inlet covered with water before the pump starts?

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

When the pump stops after pumping water out of the pit there is still about 6 inches of water left in the pit - so the inlet is covered.

I am trying something else here. I have shortened the discharge hose in the yard to just a few feet so it completely drains after the sump pump is finished. There will still be water left in the pipe that runs under the basement slab but perhaps water standing in the hose outside adds to the problem.

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 Re: Replaced Sump pump - now have air lock problem
Author: LemonPlumber (FL)

I have installed many pits that have a thousand or more gallons of water in the lines before the pump starts.when the pump does start does the water flow out the relief hole ?It means the pump is pumping.this may be a point.I am missing other wise.

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

Yes. When the pump starts the water flows out of the relief hole with lots of pressure. When the pump stops, there is not a lot of water that comes out of the relief hole. Probably just from the couple of feet of pipe before the pipe goes horizontal. I was thinking that perhaps all of the water in rest of the pipe and the hose outside the house was acting like a vacuum - preventing more water from falling back down. That was the reason I shortened the hose outside.

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 Re: Replaced Sump pump - now have air lock problem
Author: LemonPlumber (FL)

Hose is 1 1/4" ?you seem to be asking if you have a lessor pump.buy a really large hose!!!king if a straw will empty a glass quickly.

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

Yeah, the hose outside is small - 1 1/4 or 1 1/2. That seems to all Home Depot ever sells (right now they have absolutely none in stock).

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 Re: Replaced Sump pump - now have air lock problem
Author: SMSPlumbing (PA)

You do not want the whole pipe to drain back into the pit or the pump will just cycle that water. If the pipe just there at the pump drains back, that is fine.

Depending on where your float is set, that will depict where the water level will be when the pump shuts off. And then add the foot or so of water that drains back.

To me it sounds as if there is a blockage still somewhere in the pipe.

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 Re: Replaced Sump pump - now have air lock problem
Author: hj (AZ)

You are "grasping at straws" and have no idea what the problem is, and thus no way to determine how to fix it. Your description of the symptoms, as Spock would say, is "illogical", and therefore we can't help either.

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 Re: Replaced Sump pump - now have air lock problem
Author: hj (AZ)

That also has absolutely nothing to do with your problem. One possibility, and I would have to be there to see the actual installation, would be if the piping is arranged so it can "siphon" the water out of the pit once the pump starts. That could be the reason that very little water drains back when the pump stops. BUT, it would also NOT prevent the pump from removing the water when it starts.

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 Re: Replaced Sump pump - now have air lock problem
Author: mrmac (TX)

You might try an automatic air vent on the horizontal line, the kind used on chilled and heating water systems. You can valve it on the bottom and run the discharge line back to the sump pit. Maybe put a tee in with a 1/4 " valve to eliminate air and see if it helps before you buy the aav. Most commercial supply houses have them.

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

New information.

The pump is still not working properly although water shoots out of the 3/16 inch hole just wonderfully. Tonight I had to turn the pump off and on a couple of times to try and get it working. The first time I turned it off there was lots of gurgling from inside the discharge line and was water fell back into the pit there were also some air bubbles coming out.

The pump still would not work so I did what I have done numerous times before - with the pump running, I loosened off the clamp where the discharge line is joined in the horizontal area above the pit(where I cut it to remove the original pump). This causes air to rush out of the joint under pressure. When water starts spitting out instead of air I tighten the clamp and turn off the pump. When I turn the pump back on again it pumps just fine.

When it finishes its job a bit of water falls back into the pit and some air bubbles too.

The pump always spits water out of the 3/16 inch hole with good pressure but it can't seem to get by air trapped in the line until I bleed the air out. I have flushed out the line by inserting a hose outside the house and it runs freely down into the pit so there does not seem to be a blockage.

Any ideas as to how this air accumulates in the line in the horizontal area? Someone mentioned in an earlier post that this should not stop the pump from discharging the water but it certainly seems to.

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 Re: Replaced Sump pump - now have air lock problem
Author: jerco (MD)

I think it's safe to say that we are as baffled as you are. Air lock should only occur at the pump. If water is spraying out of the hole then the air lock is solved and water should push all the way through the line regardless of additional air pockets along the way. I don't know what to tell you.

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 Re: Replaced Sump pump - now have air lock problem
Author: fishEH (IL)

Sounds like your check valve in installed backwards. You shouldn't be able to run a garden hose at the discharge end and have the water come into your sump pit.

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 Re: Replaced Sump pump - now have air lock problem
Author: rickster (NY)

Here's where I think the problem lies.

Your pipe comes UP out of the sump pit, goes horiz, then goes BACK DOWN and under the slab. That turn >> DOWN is the problem.

In that DOWN segment, right after the pump cycles off, the falling of that last volume of water downward sucks air into the line because the pump has stopped delivering water into the pipe. An air pocket forms in that vertical section of pipe. THen the pump cycles on again and that air bubble gets pushed along. And then the next few cycles adds to the ammount of air. And voila! Soon, you have an air lock in the piping. This air can't escape through your relief hole because it is drilled upstream of this segment of piping.


Solutions?

(1) Not easy: Put an air relief hole downstream of that DOWN segment of pipe.

(2) More reaonable:

Run your pipe directly from the sump pump up so many inches, then one 90-degree turn towards the horizontal run of pipe under the slab. ( No upsies and downsies and upsies! ) So that means a little concrete demolition. (Rent a heavy duty Masonry drill with jackhammer feature at Home Depot. Drill holes then switch to jack hammer mode to break it up. )

I can't guarantee this is the problem, but it is a good possibility.

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 Re: Replaced Sump pump - now have air lock problem
Author: Sense2k (NJ)

Hello
I just joined. I have the exact same problem.
Doug, did you find out exactly what causes this?
Did you find a solution?
i will try to do same thing - disconnect hose at check valve to let air out etc

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 Re: Replaced Sump pump - now have air lock problem
Author: doug_mb (Non-US)

I still have the problem which I believe is probably caused by the discharge line which runs under the concrete floor being bowed up (due to the house settling). I deal with it by putting the sump pump on a timer which will allow the pump to run for 30 minutes and then shut off a few times a day. If the pump is not really pumping and the pit is not being emptied the water (and air) that is in the discharge line will then run back into the pit. This clears the air lock in the line without my having to be there and the pump will work properly the next time the timer allows the pump to start.

Still do not know why this issue only started after the initial pump failed.

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