Sump pump constantly short cycling

[ryanmar814]

Hello,

Is it ever considered normal for a sump pump to short cycle aka going off every 10 seconds constantly?

My landlord left the sump pump unplugged after installing it himself and the basement flooded. After plugging it back in, it constantly cycles every 10 seconds without fail, 24/7. It had been short cycling for several days. He came back and unplugged it to "let it evaporate" for a week but he's plugged it back in and it went straight back to short cycling. The sprinkles are off and it has not rained or snowed. He said we should just let it constantly short cycle until water evaporates.

To me, it sounds like the pump isn't able to fully discharge the water so some falls back into the pit, thus triggering the pump to go again. I think this is a catch valve issue.

It's a 3/4 hp in what looks like a 7ft sump pit.

His initial fix was to put a rock in the bottom of the pit. That did not work.

Could someone please advise on if short cycling is ever "acceptable"? It is my understanding that this will cost quite a bit in electricity and will burn the pump motor out.

Thank you so much

 

[SHEPLMBR]

How far total is it going up? It could be too big of a pump.

 

[ryanmar814]

How far total is it going up? It could be too big of a pump.

Hello! It looks like there are a few inches (perhaps 4 - 5 inches) of water the pit.

 

[SHEPLMBR]

Did your landlord adjust the float? Some people believe the higher the horse power the better. It's not. Pumps are made to run. When I said total up, I meant feet up until it horizontals out of house.

 

[ryanmar814]

Did your landlord adjust the float? Some people believe the higher the horse power the better. It's not. Pumps are made to run. When I said total up, I meant feet up until it horizontals out of house.

Sorry about that! No, I don't believe he did. I'd say it's probably about 11 - 12 ft. It's standard ceiling height plus a foot or two on the outside of the house.

 

[MicEd69]

Are you sure the sump is 7 feet deep? They should be something more like 3 feet deep. How far is the horizontal run of pipe from the sump to the discharge point?

There should be a check valve relatively close to the pump in the discharge line. I would suspect the check valve is stuck open and the water in the pipe is draining back into the sump and the pump is pumping the same water back up the pipe.

And you are correct, the pump will fail way prematurely if it cycles every 10 seconds for days or weeks.

If the sump is truly 7 feet deep and is an open pump to collect water from under the foundation and from around the base of the basement wall, depending on where you are, it is conceivable that you are pumping water from below the current water table. Probably not, but conceivable.

The check valve is the likely culprit, and I would check that first. But as SHEPLMBR said, the pump could be too large. A throttling valve can be installed in the pump discharge line to fix that issue if it is contributing to the problem.

 

[ryanmar814]

Are you sure the sump is 7 feet deep? They should be something more like 3 feet deep. How far is the horizontal run of pipe from the sump to the discharge point?

There should be a check valve relatively close to the pump in the discharge line. I would suspect the check valve is stuck open and the water in the pipe is draining back into the sump and the pump is pumping the same water back up the pipe.

And you are correct, the pump will fail way prematurely if it cycles every 10 seconds for days or weeks.

If the sump is truly 7 feet deep and is an open pump to collect water from under the foundation and from around the base of the basement wall, depending on where you are, it is conceivable that you are pumping water from below the current water table. Probably not, but conceivable.

The check valve is the likely culprit, and I would check that first. But as SHEPLMBR said, the pump could be too large. A throttling valve can be installed in the pump discharge line to fix that issue if it is contributing to the problem.

I think it's far more than 3ft, although my eye could absolutely be deceiving me. The horizontal run is probably around 25ft, possibly more. Vertical is about 11 - 12ft. There is 1 visible 90 degree point. Based on the height on that angle there are probably more.

Is it expensive for a sump pump to run that often (in electricity)? I see that it costs about $30 a month average to run a sump pump that goes off about 8 times a month in good conditions. I'm very worried that with this pump going off... over 8 thousand times a day that my electric bill is going to be outrageous. No worries if this is unknown.

I see that there is a check valve installed but I can very clearly hear water splash back down which leads me to believe it's not functioning/installed correctly.

 

[MicEd69]

Well, it surely seems like the check valve is stuck open. Assuming your piping is 1 1/2", there will be about 4 gallons of water in the line that long. And that is about enough water to make the level rise about a foot in a 3' sump, which in turn would cause the pump to come back on.

Raising the pump would simply raise the stagnant water level in the sump and would not help your situation at all.

As far as the cost to run a sump pump, it all depends on the duration the pump runs. So, your $30 a month isn't necessarily true.

However, we can take a guess at your situation. Your 3/4 HP motor will take around 1 KW plus or minus. If it actually runs half time (10 seconds on and 10 seconds off) it will be running around 360 hours each month. Assuming an electrical cost of $0.15 per kWh, that would be $54 per month. That's a lot of money to pump the same water up a pipe just to let it drain back down into the sump 10 seconds later.

A 3/4 HP sump pump should be pumping around 50-55 GPM with no restriction other than the check valve and piping. So, if the 10 seconds on/off is actually 10 seconds, and volume of the pipe is around 4 gallons, that only equates to 12 GPM if that is actually recirculating the same water. You may want to verify that there isn't a throttling valve already in the piping. That won't resolve the issue but would explain the flow rate and timing discrepancy.

 

[ryanmar814]

Well, it surely seems like the check valve is stuck open. Assuming your piping is 1 1/2", there will be about 4 gallons of water in the line that long. And that is about enough water to make the level rise about a foot in a 3' sump, which in turn would cause the pump to come back on.

Raising the pump would simply raise the stagnant water level in the sump and would not help your situation at all.

As far as the cost to run a sump pump, it all depends on the duration the pump runs. So, your $30 a month isn't necessarily true.

However, we can take a guess at your situation. Your 3/4 HP motor will take around 1 KW plus or minus. If it actually runs half time (10 seconds on and 10 seconds off) it will be running around 360 hours each month. Assuming an electrical cost of $0.15 per kWh, that would be $54 per month. That's a lot of money to pump the same water up a pipe just to let it drain back down into the sump 10 seconds later.

A 3/4 HP sump pump should be pumping around 50-55 GPM with no restriction other than the check valve and piping. So, if the 10 seconds on/off is actually 10 seconds, and volume of the pipe is around 4 gallons, that only equates to 12 GPM if that is actually recirculating the same water. You may want to verify that there isn't a throttling valve already in the piping. That won't resolve the issue but would explain the flow rate and timing discrepancy.

Thank you so much for your explanation! I will try to see if there is a throttling valve and get the check valve checked.

 

[CT18]

Some water will drain back from the check valve to the pump so it does air lock. They will drill a relief hole in the pipe between the pump and the check valve. As long as it isn't draining the whole vertical rise. Does it drain back enough to cause the pump to turn back on.