How to repair leaking valves under bathroom sinks

Written by paul massey
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Simple sink valves, found in the cabinet beneath the bathroom or kitchen sink, last for many years. They have almost no moving parts and are rarely even thought of, until there is a leak. Over the life of these valves, mineral deposits from the tap water can build up or the small rubber gaskets inside deteriorate and leaking occurs. Simply replacing one of these inexpensive valves is the quickest and easiest repair when you find a leak.

Skill level:

Things you need

  • Crescent wrench
  • Small bucket
  • Plumber’s emory cloth
  • Teflon thread tape
  • New sink valve

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  1. 1

    Turn off the water supply to the to the sink valve being repaired. This is most easily done by turning off the primary water main to the residence, typically located at the exterior of the house.

  2. 2

    Open the sink’s faucet to relieve of any back pressure to the fixture and allow some of the standing water in the water line to siphon back from the sink valve.

  3. 3

    Position a small bucket below the sink valve being replaced to catch any water left in the line when it's disconnected.

  4. 4

    Disconnect the water supply line to the sink faucet with an crescent wrench by turning the hex nut connecting the line to the sink valve counterclockwise until the nut is free of the valve’s threads. Let the small amount of water remaining in the line drain into the bucket positioned in Step 3.

  5. 5

    Remove the sink valve by loosening and removing the large hexagonal nut at the base of the valve with a crescent wrench. Pull the sink valve off of the copper water line.

  6. 6

    Slip the small brass compression ring off the copper water pipe to remove the valve’s hexagonal nut removed in Step 5. Buff the copper pipe with a piece of plumber’s emory cloth to remove any corrosion or mineral build-up from the copper pipe.

  7. 7

    Remove the large and small hexagonal nuts from the new sink valve. Wrap the threads at both connections with three full layers of Teflon thread tape.

  8. 8

    Slide the large hexagonal nut from the new sink valve over the copper water line, with the threads outward, followed by the brass compression ring. Slip the new sink valve onto the pipe. Thread the large hexagonal nut onto the valve and tighten until snug using a crescent wrench.

  9. 9

    Reconnect the water supply line from the faucet to the smaller threaded connection on the sink valve and tighten until snug.

  10. 10

    Restore the main water supply to the sink. Open the new sink valve by turning the sink valve’s control knob counterclockwise. Check the new sink valve’s connections for leaking and tighten the connection, if necessary.

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