Sewage Ejector Pump Problems

This is a perplexing problem. I have a sewage pit in the basement for the whole house. In the pit are two ejector pumps, Hydromatic SK100's. They pump through a 2" pvc pipe to the city sewer main with a lift of about 25 feet. Only one pump runs at a time and they alternate.

Everything was fine for 12 years. They never missed a beat. Then, after a week of vacation this year the pumps would run, but not pump out. I could only get them to work by loosening the union between the check valve and the pump and letting trapped air out.

So I bought a new Grundfos SE75 (this pump has a vortex impellar) because the parts for the Hydromatics were so expensive. I assumed the old pumps had eroded housings and impellars and could not build enough head.

Well the new pump does the same thing as the old ones. I still have to loosen the union to bleed the air.

I put an accurate gage on the outlet and when the flow is going I see about 12.5 psi. When the pump is off, about 8.5 psi. These pressures are very consistant and stable, so I don't think there is a clog. The gage is about 6' above the pump suction.

Next, I am planning to open the pit cover and drill a small hole in the pipe to vent the air, but I still don't know why the old pumps worked for 12 years without the hole and now nothing seems to work.

Any advice would be appreciated.

Thanks.

grease in pit???

we have run into the problem of grease
building up in a sewage pit over time
and a pump wont pump grease very well....at all


you might have to see into having the
pit cleaned out of whatever has jelled up in it...

sewer ejector pump problems

I don't think there is a grease problem. I considered this, thought that maybe the suctions were being blocked. I emptied the pit and it was pretty clean. I flushed out what there was and still the same symptoms.

something else

have you just considered having the line going out
of the house to the sewer snaked???


I wouldent think that a pressureized line would
have this problem, but i guess its feasalbe if the line
sat dromant for a few weeks perhaps it had
developed a clog

Check Valve?

I fixed one this spring that had the check valve stuck shut. These pumps produce low head and won't overcome a stuck valve. I suspect that it is not air because you should not get air if the pressure gauge reads 8.5 psi.

You also said the new pumps which are 75's (old ones being 100's) are acting the same way. Could it be you bought the wrong (too small) pumps? Maybe those vortec impellers can't make the 25 feet of head you need to even get the sewage up to the sewer.

The expensive parts you mentioned were probably the parts for a grinder pump. Grinders make far more head than vortec impellers do. If the sewer main has pressure in it, you may not have enough pump to overcome that pressure.

bob...

Sewer ejector pump problems

I am hoping that there is not a clog. This would be a pretty pricey cleaning since the pipe is about 150 feet long.

The impellar for the old pump alone was $275.00

The new Grundfos 75 published max. head is nearly the same as the old 100. I just doesn't pump quite as fast, which is ok since it only needs to run for a few minutes maybe once or twice a day.

I agree that it seems like the pumps can't overcome the head caused by the water in the pipe(8.5 psi) and the closed check valve.

What do you think about drilling a hole in the pipe between the pump and the checkvalve? I've heard of this before. Why do you think this works?

Thanks.

Drill hole

From your first post I would have assumed that you were already going to do this. We always recommend to drill a 3/16" hole in the discharge pipe somewhere near the top of the pump but below the check valve! When you first mentioned that when you release the coupling for the check valve and the pumps worked because the air escaped, that's the problem!

The pumps are becoming air locked, this is like holding a glass upside down in the water and the water will not go in to the glass until the air escapes! The reason it works is because when the pump is done running, the water that is left in the vertical part of the pipe comes rushing back down into the pit and creates a vacuum causing the check valve to slam shut and trapping air between the water and the check valve, so when the pump turns on again, the impeller is just spinning and cannot grab a hold of the water because the air has no where to go! The small hole lets the air escape and the water gets pushed up and out!

Hope this helps