Kitchen Sink Drain Issue? Advice from plumbers and DIY-ers appreciated

trex on 29/08/2017 - 23:20

My kitchen sink drains into the ground via a S trapwith dishwasher connection. The S trap for my kitchen sink has unequal water levels where the water level is higher on the sink's side and lower on the drain side. The difference in water level is quite substantial, around 10-12cm. This seems to indicate that there is air pressure building up on the drain side possibly due to blockage. As far as I can see, water is not backing up and is draining properly albeit with the difference in water level in the S trap. My dishwasher is connected to the s trap just below the water level so water tend to be sucked back into my dishwasher. Appreciate any advice on what the problem may be. Could it be blockage in the vent? Or is it simply blockage in the drain? I've tried using Liquid Drain Clean poured directly into the drain pipe but it didn't help. I'm thinking of using an auger next but wanted to get some advice first.

Thanks in advance for your inputs.

Home & Garden

Comments

  • [Deactivated] on 30/08/2017 - 00:59

    I'm not a plumber or an Einstein but why is your dishwasher connected below water level of the S pipe.

    • trex on 30/08/2017 - 10:38

      As seen from the S trap from my link, the dishwasher connection is above the water level but due to the issue I'm having with the air pressure on the drain's side, the water level rest above the dishwasher connection.

  • Richardc on 30/08/2017 - 01:06

    how do u know they r uneven?

    • trex on 30/08/2017 - 10:39

      I used a flash light to shine through the S trap so I am able to see the water level on each side.

      • altomic on 30/08/2017 - 11:50

        Could it be that you are seeing a very dark stain through the pipe?

        It does sound puzzling.

        • trex on 30/08/2017 - 11:55

          It's not a dark stain since I've cleaned the s trap spotless. I can see the water level go up or down when I use the sink.

  • Cheeper on 30/08/2017 - 04:14

    When you empty the sink what is the flow like… excessively slow?
    Gunk and fat builds up in all them over time and a couple of jugs of boiling water can usually clear them out.
    You can take out the s bend and give it a clean out too… surprising what you find in them.
    If you had a blockage futher down the drain from tree roots etc your shower & toilet would back up.
    Make sure your dishwasher hose where it connects the s bend is held up as high as possible.
    You can get a coiled drain and sink cleaner and feed it down if there still seems to be some obstruction.
    https://www.bunnings.com.au/kinetic-180cm-pipe-drain-cleanin…
    Also check for access points outside and try running your hose in there to clear out any obstruction.

    • trex on 30/08/2017 - 10:41

      It doesn't drain slow at all, that's what got me stumped. My first option before using the liquid Drain Clean was hot water from the tap running for over 3 minutes and later on using bi-carb soda and vinegar directly into the drain.

      Outside access point is buried is not accessible easily. Guess it may be time for me to start digging :D

      • Cheeper on 30/08/2017 - 11:42

        No need to dig if your water is getting away fast.
        Is your DW hose hooked up high like in the pic in this link (down the page)?
        http://www.startribune.com/the-most-common-dishwasher-instal…

        • trex on 30/08/2017 - 11:54
          +1

          My DW is hooked high at the rear of the dishwasher as the cabinet space prevents it from being hooked high under the sink. It's been like this for over 2 years and DW was operating with no problems. Not sure about then equal water levels though as I've never noticed it before.

  • SnoozeAndLose on 30/08/2017 - 06:09

    Bicarb soda and vinegar is your best friend, go youtube and search.

    • trex on 30/08/2017 - 10:42

      Thanks, bicarb soda and vinegar has already been attempted.

  • [Deactivated] on 30/08/2017 - 06:31

    Caustic soda and boiling water, and stand back

    • trex on 30/08/2017 - 10:42

      The liquid drain cleaner that I used was caustic but I used cold water based on the instructions on the drain clean. :)

  • Euphemistic on 30/08/2017 - 06:59

    If the water flows away properly I don't understand how it can be higher on one side than the other. The whole idea of that is the water levels out to create a block for smells coming back up the pipes. The water in the sink side should be no higher than the lowest point on the drain side.

    Don't tip nasty chemicals down there if you think it is getting back to the dishwasher, probably won't be good for it.

    What happens if you disconnect the dishwasher, does water pour out the connection? Our dishwasher connection is higher than the s trap water level so doesn't leak at all. Try disconnecting it and blocking the inlet, fill the sink up, then let the plug out. If it drains out freely, it isn't blocked.

    • trex on 30/08/2017 - 10:44

      I've tried draining the sink using the plug. No issues at all.

      When I disconnected the dishwasher from the s trap, water actually started shooting out as it was under pressure.

  • Tabbycat on 30/08/2017 - 09:32

    The simplest way is just to disconnect the trap to see what is going on in there. Unscrew the fittings below and above the S-bend. Maybe mark them all first so they go back the same way, and watch for the rubber washers that might fall out.
    Also have plenty of rags around to mop up, and don't empty the water trapped in the U-bend down the same sink.

    • trex on 30/08/2017 - 10:46

      I had the same thought and had taken off the s trap and gave it a good clean but it didn't help.

  • Cheeper on 30/08/2017 - 11:59

    In a s trap wouldnt it be normal for the water to be higher on the sink side as the water in the trap creates a small restriction? IE: it takes the weight of the water in the inlet side to force the water over the top of the outlet side.

  • Cheeper on 30/08/2017 - 12:08

    "water tend to be sucked back into my dishwasher."
    That is the real problem..
    The first thing I would check is the DW drain check valve. Most are easy to get at and they can get things caught in them and need a clean out occasionally.

    • trex on 30/08/2017 - 21:55

      My first impression was that there's something wrong with my dishwasher but after trouble shooting I think the problem here is that the dishwasher outlet sits below the water level in the s trap.

      Water remaining in the DW drain hose will cause a siphon action when it drains down from the top after the pump stops. There is no problems at all in my dishwasher retaining water during wash cycle or when it pumps the waste water out hence I don't think there's any problem with the DW check valve. Checking online, problems with DW check valve usually results in DW not draining or leaking water.

  • Tabbycat on 30/08/2017 - 17:25
    +1

    Has the dishwasher outlet hose got a loop in it so that it is higher than the level where it connects to the sink drain? This is supposed to stop it draining back to the dishwasher.

    • trex on 30/08/2017 - 21:56

      Yes, there is a loop but as I mentioned in my reply to xywolap, I suspect the water draining back is due to siphon action since the DW outlet is below water level in the s trap.

      • Cheeper on 30/08/2017 - 23:37

        But if your check valve is working there should be no siphoning action from the DW?
        It must be faulty if it is syphoning.. imo lol

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