How To Plumb Your Sink

Everyone should have a basic understanding of the plumbing structures in their home. That’s why we’ve put together this quick guide on how to plumb your sink. While every sink will be different, these are the basic components that every sink should have. We’ll go over what each component does, where to find them, and how to be sure it’s functioning properly.

Soon you’ll be ready to tackle the minor plumbing issues that might arise with the sinks in your home!

Shutoff Valves

What They Are

These important components of your bathroom sink are the first thing you should learn to identify. These allow you to turn off the water supply to your sink if you need to make repairs, or if there is a plumbing emergency.

By tightening these valves, you can turn off the water supply to your sink without turning off the water supply to the rest of the house.

What They Look Like

Shutoff valves are small, often metal, and will have a flexible supply tube or hose that connects it to the faucet.

The knobs on these valves are often football-shaped. These can be rotated to either turn off or turn on the supply of water.

What To Watch Out For

Old valves can corrode. When this happens the inner workings fail to fully stop the flow of water when you need it to.

Corroded valves can also spring leaks around their joints. If you see water on the outside of the supply valve, you probably need to have it replaced.

Supply Tubes

What They Are

Supply tubes carry water from the shutoff valve to the faucet of the sink. A properly fitting supply tube should be just long enough to reach from the shutoff valve to the faucet. If your supply lines are too long or have loops in them, you might want to consider a replacement.

What They Look Like

The tell-tale sign of a supply line is that it is flexible. It needs to be in order to effectively reach the faucet of your sink. They can be made from an array of materials like stainless steel mesh, braided polymer, or even chromed copper. But no matter what they are made of they will be bendable.

What To Watch Out For

Over time these tubes can corrode and crack, and the connection points at either end can degrade causing leaks.

Drain Tailpiece

What It Is

The main connection between your sink’s drain assembly and the P-trap. If a clog occurs in this portion of the drain, the tailpiece can be removed to clear the clog.

What It Looks Like

The drain tailpiece is a short, straight section of pipe that connects to the bottom of the sink drain. It attaches to the drain assembly on one end and the P-trap on the other end. You may notice a small opening on the back of this piece that allows for the connection of the rod that raises and lowers the popup stopper.

What To Look Out For

It is essential that this piece be in proper alignment during installation. Otherwise, there can be leaks at the connections.

If your popup stopper stops working, check the back of this piece. This is where the popup control rod connects and it may have become disconnected.


What It Is

The P-trap uses a series of bends to create a water trap in the drain line of your sink. It gets its name because a properly installed P-trap will look something like a sideways letter “P”.

The purpose of this trap is to create a barrier of water that prevents sewer gasses and pests from entering your home through the drainage pipes.

What It Looks Like

There are two parts to a P-trap: a curved U-bend and the trap arm. As water flows from your sink’s drain and enters this U-bend, a certain amount of it remains there, preventing sewer gasses from passing the U-bend.

What To Look Out For

Proper maintenance of the slope, positioning, and water seals are crucial. If any of these are neglected the flow of waste water can be impeded.

The P-trap is also a prime location for hair and debris accumulation. Regular cleaning of P-traps is needed to prevent this from building up into a clogged drain line. Be careful, though. The advice you read about unclogging drains is often wrong.

Drain Pipe

What It Is

The drain pipe carries wastewater from the sink to the main plumbing drainage system. It attaches to the P-trap assembly and allows water to flow through the pipes that run inside the walls. This pipe might come out of a wall or floor, depending on the plumbing configuration already in place.

What It Looks Like

Most drain pipes are made from PVC, ABS plastic, or chromed metal. They have a downhill slope so gravity can keep the wastewater moving in the right direction. This pipe might lead into a wall or floor, depending on the plumbing configuration already in place.

What To Watch Out For

Improper slope can prevent waste water from draining correctly, so be sure your drain pipe attaches to your P-trap with a downhill slope.

Like the P-trap, the drain pipe is prone to clogs from buildup and mineral deposits. Corrosion can also cause cracks and leaks, especially in older metal pipes.

Ready For (Almost) Anything

Now you know the basics of the plumbing under your sink. With this understanding in mind, you’re ready to tackle some of the most common plumbing issues that arise.

But if something goes wrong with your plumbing that is beyond what we’ve covered here, don’t hesitate to give us a call! Our professional plumbers are ready to help you solve any plumbing problem!


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We are a full-service Gainesville plumbing company specializing in remodels, repipes and plumbing repairs.

If you need plumbing service, J.W. Freeman is here to help. Get in touch with us today.

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