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Get to Know Your Kitchen Sink Plumbing

pipes under kitchen sink

Your kitchen sink plumbing has to deal with running water, heavy pans, hot oil and food scraps. It is bound to have occasional issues. Here is a kitchen sink plumbing anatomy lesson to help troubleshoot any problems.

How the Water Gets into the Sink

Your water supply lines typically have simple and easily accessible control valves under the sink - the first place to check if water isn’t flowing properly. Switch off the valves for kitchen sink plumbing repairs and troubleshooting, and remember the same valves typically control water flow for the dishwasher.

At the valves, the pipes connect tightly to sink supply tubes. In most sinks, these two water lines are controlled by one handle and pour out of the faucet in one stream. There are at least three types of single-handle faucet:

  • Some have a metal ball with holes that line up with rubber-sealed water inlets. The inlets can be easily clogged with particles, so clean the inlets if water flow is slow or erratic, and replace worn rubber seals.
  • Others have a pair of ceramic or plastic discs that line up to allow water flow. It may be possible to pull apart the cartridge and flush out the discs, but many models do not separate and the whole cartridge must be replaced if the disks are cracked or clogged.
  • Other faucets have a grooved cartridge that controls water flow. Again, the whole cartridge must be replaced rather than repaired, and keep in mind that some models require a manufacturer-specific pulling tool.

Finally, the water flows into the sink through an aerator or sprayer, which may be mounted in the faucet or as a separate unit. If water is not flowing smoothly from the spout, remove and flush out the aerator. If the aerator is regularly clogged, it may mean your pipes are corroding or your water is impure. Consider having the lines cleaned or install a water filter.

How the Water Gets out of the Sink

Water flows back out of the sink through drainpipes - hopefully. Water can leak out of a strainer, disposal or pipes. A solid, smooth ring of plumber’s putty around the strainer often prevents leaks from the basin.

The in-sink garbage disposal should be tightly affixed with a mounting ring. A disposal simply chews up your food scraps into drain-safe pieces. If the disposal won’t turn on, check the reset button on the unit.

The rest of the plumbing is straightforward. Each length of pipe is attached with a washer and nut. Leaks often cannot be fixed by just tightening nuts. Worn seals and washers cause most problems, but they are usually cheap and easy to replace.

If your drain is clogged beyond a plunger’s capabilities, check the trap - the bend or loop under the sink. The trap keeps noxious sewer gases from blowing into the house, and traps clogs. Food may be stuck in the trap, blocking water flow.

Kitchen sink plumbing may have plenty of parts, but troubleshooting problems should be fairly straightforward with a basic understanding of the system.


Author Steve Graham is an expert on green building who writes for several home improvement publications. He's full of great, practical home improvement answers, and incidentally, he's pretty funny-so send him a message.

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