How to Unplug a Sink That a Dishwasher Is Backing Up Into

Written by richard may
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How to Unplug a Sink That a Dishwasher Is Backing Up Into
A blocked sink can cause water damage. (kitchen sink image by jedphoto from

Providing good drainage for a dishwasher is vital for it to function properly. If your dishwasher drains into the sink and the sink is blocked, it can cause an overflow, damaging your property and, if you live in an apartment, the neighbour's property below you. If your sink backs up while the dishwasher is draining it needs immediate attention. Most sink blockages are easy to clear and do not require a plumber.

Skill level:

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Things you need

  • Plunger
  • Dishcloth
  • Bucket
  • Bicarbonate of soda
  • Vinegar
  • Sink unblocking solution
  • Wire coat hanger

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  1. 1

    Hold the plunger in both hands and cover the plughole with the rubber suction cup. Move the handle vigorously up and down for a few seconds while keeping the rubber cup firmly over the plughole. If the waste pipe is completely blocked, trapped water can escape into the sink overflow and then back into the sink. If this happens the overflow needs to be blocked to ensure a vacuum is maintained during plunging. Hold a dishcloth firmly over the overflow with one hand while using the plunger in the other hand.

  2. 2

    Pour one cup of bicarbonate of soda into the plughole and add four cups of malt vinegar. The two ingredients will react together and begin to fizz. Leave for half an hour and check if the sink is still blocked.

  3. 3

    Fill the plughole with a sink unblocking chemical and leave for the time stated on the packaging. These chemical solutions can be purchased from hardware stores.

  4. 4

    Place the bucket beneath the sink’s “U” bend or trap if the sink is still blocked. The “U” bend is usually made from plastic and connects the plughole to the domestic waste pipe.

  5. 5

    Unscrew the “U” bend by twisting the retaining nuts surrounding the pipe. Remove the “U” bend and allow residual water to drain into the bucket.

  6. 6

    Remove any debris in the “U” bend with your fingers or a straightened wire coat hanger. Once the “U” bend is clear, secure it to the waste pipe and sink ensuring the retaining nuts are secured tight. Leave the bucket in place and check for leaks.

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