Sump Pump Humming - Not Moving Water- PERPLEXED!

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by chuck b, Sep 12, 2020.

  1. chuck b

    chuck b sea-bee

    Jan 19, 2011
    levering, michigan
    59FFAC42-55B5-4F98-B47E-662B2EE7A79B.jpeg 2C7D6256-16DF-41C3-A441-7E1AAE677555.jpeg

    Hi Guys,

    I am having a perplexing problem. Frankly I am puzzled with the following issue:

    I noticed my pedestal (motor above crock) sump pump “humming” but not moving water recently. Since it was some 20 years old I figured it needed replacing.

    I replaced it with a submersible Liberty 1/3 hp pump ultimately (2nd new pump). I followed the instructions and drilled a 1/8” anti-airlock hole aiming down on an angle per the instructions just above where the discharge line is connected to the pump as instructed. Liberty pump also has a built-in anti-air lock hole at the side of the pump although they suggested another 1/8” hole be drilled as I did.

    The Liberty was the second new submersible pump I installed. I installed another brand first and experienced the same humming problem At the end of the pump activation resulting in a partially empty pit. I took it back and got the Liberty pump which repeated the problem.

    The unlikely odds of all three pumps experiencing the same humming problem may be a clue to what the problem is I hope. I wish I still had my original pump and could test it in the laundry tub but it sent out in the trash.

    I need to describe the 1 1/2” pvc outlet discharge pipes (2) configuration. I also have a water powered back up pump installed you will note. Photos attached of the discharge pipe configurations.

    Exiting the crock from the pump the discharge line is “wyed off” near floor level. The straight end of the pipe then passes a brass shut off valve and then a (new) check valve before exiting the house to drain outside. I have kept this valve closed for 20-years to avoid pooling water outside.

    The “wyed off” discharge pipe then travels a short distance before a 90° upward directed fitting, through a check valve (I am thinking that that black fitting is a check valve it has an arrow indicating water flow direction on it although I did not inspect it), then passing a just installed BOCA air admittance valve (I just installed it thinking the line needed air although the sump is only 6 feet from a stack drain line and worked fine for many years), then another brass shut off valve that is kept in the open position that is connected to the sanitary sewer line.

    I tested the 2nd new submersible Liberty 1/3 hp pump this time, and it worked fine exiting through the sanitary sewer , but after a couple cycles at the end of the cycle before it completely discharged the water at the bottom it started humming and not moving water just like the first replacement pump and for that matter the original pump.

    Trying to troubleshoot why the pump was humming I opened up the gate valve leading outside keeping the wyed off discharge line to the sanitary sewer open as well, and the pump miraculously started working and discharged the water forcefully outside. I did not know if any water was flowing through the sanitary sewer line since there’s no way to inspect it but it didn’t sound like it was. It was vibrating but I didn’t know if water was actually running through it.

    So I am guessing that the likelihood of all three pumps humming at the end of the cycle rules out a pump problem?!

    But the original pedestal pump worked fine for many many years with this discharge pipe configuration, i.e. gate valve to the outside closed, and gate valve to the sanitary line open.

    I thought perhaps believing the first pedestal pump was defective, the submersible pumps had different properties regarding discharge and the need for air which is why I added and air admittance valve. Didn’t solve issue.

    I now have the pump discharging water outside while the sanitary sewer valve continues to be open as well, but I really don’t think water is running through it. Perhaps the path of least resistance is straight up at the wye.

    The outside discharge pipe is creating a holy mess outside and I prefer to discharge the sump crock water to the sanitary line like I did successfully for 20 years plus.

    Before I cut up open at great difficulty since there are walls up as it’s a finished basement where the line to the sanitary runs, would I need to remove and inspect the discharge PVC line to the sanitary to see if perhaps over time it started clogging up with minerals etc. over the years? But why would the pump work emptying the pit until the water level got to the bottom? Would the water pressure ultimately create an air back up near the end of the cycle and created an air bubble?

    I did not inspect that black (see pic) alleged (is it a check valve) check valve on the sanitary line could that be a problem? Did I mention that has a direction for water flow on it but it’s certainly not a conventionally looking check valve. Or is it just some kind of union?

    Could the water pressure create an air back up near the end of the cycle? Would the pump then stop pumping (but humming) at the end of the cycle perhaps be accumulating air? Why hadn’t it done that in 20 years? Is there a difference between submersible and pedestal type pumps that could create this problem?

    By the way before installing the first replacement pump, I completely cleaned and wet vacuumed the entire pit and placed both pumps on bricks to avoid sucking in sediment.

    I tried to be as descriptive as possible and apologize for the lengthy somewhat redundant post.

    It just seems to me that the discharge pipe configuration is where the problem is since all three pumps exhibited the same humming issue, but what perplexes me is that it worked that way for 20 years.

    Thanks very much for your time. Would be willing to offer my cell number and personal email address if helpful.

    Thanks a lot.

    Chuck B (Michigan)

    Attached Files:

    Last edited: Sep 12, 2020
  2. fitter30

    fitter30 Active Member

    Feb 2, 2020
    Retired service tech
    Peace valley missouri
    Both gate valves in the pumps discharge line count the the turns from close to open to see if there the same. The one going outside you know its good but the one going to plumbing might have a broken gate and not open 100%. That black fitting with the arrow is a check.
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  4. Tuttles Revenge

    Tuttles Revenge In the Trades

    Oct 15, 2014
    TL DR:

    That system looks messed up. Is that pipe with the black "check valve" a gravity drain entering into the discharge of the pump? Why would anyone do that? The gravity drain should just dump into that sump pit by itself eliminating the need for the gate valve and backflow.

    Have you tried just running the pumps in a bucket with a small section of pipe in your yard maybe to see if they function at all?
  5. chuck b

    chuck b sea-bee

    Jan 19, 2011
    levering, michigan
    Thanks for all the suggestions.

    The black fitting is a check valve on the way out to the sanitary drain.

    I finally disassembled it and found that the flapper hinge was broken off and the round stopper was bouncing around inside which caused the problem. I put in a new check valve and everything is working fine thanks for the thoughts.
    Tuttles Revenge likes this.
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