Under Sink Water Pipes: A Comprehensive DIY Installation Guide

Installing under sink water pipes can be a straightforward DIY project if you have the right tools and a basic understanding of plumbing.

The first step is to shut off the water supply to the sink, which is usually located near the water shut-off valves under the sink.

You'll need to locate the shut-off valves and turn them clockwise to shut off the water supply.

The main pipes under your sink are usually 3/4 inches in diameter, while the branch lines that feed individual fixtures are 1/2 inch in diameter.

There are three main types of connectors for faucet supply hoses: 1/2-inch slip joint, 1/2-inch outside diameter, and 3/8-inch outside diameter.

A 1/2-inch supply pipe typically terminates with a shutoff valve, which determines the connector size on the faucet hose.

To determine the correct connector size for your faucet, look for the outlet port, which is the one that interests you when installing a faucet.

The two most common types of faucet supply hoses are made from flexible plastic and braided metal, with metal ones lasting longer and costing a bit more.

Corrugated copper used to be a common type of water supply line, but it's no longer commonly used under sinks due to its tendency to become rigid and leak over time.

A supply tube is a braided wire or plastic mesh tube that supplies water to the bathroom faucet, always coming in pairs for hot and cold water.

Supply tubes are connected to the bottom of the sink faucet and shutoff valves with attached nuts, and sometimes fail, requiring replacement.

Here's a quick reference guide to the common types of faucet supply hose connectors:

Under sink plumbing components are crucial for a functioning kitchen. The faucet supply lines, which are flexible hoses, connect the hot and cold water supply to your faucet.

The P-trap is a U-shaped pipe that holds water to prevent sewer gases from entering your home. It's a vital component that keeps your kitchen smelling fresh.

Shut-off valves, located under the sink, control the water supply and allow you to turn off water to the faucet without shutting off the main water supply. They come in pairs, one for hot water and one for cold water.

Here are the key components of under sink plumbing:

The shutoff valve is a crucial component of under sink plumbing, and understanding its function can save you a lot of trouble. It's a metal or plastic valve located between the incoming water supply pipes and the supply hoses or tubes that connect to the sink faucet.

Most shutoff valves have an oval, football-shaped handle that you turn to open or close the valve. You'll typically see them in pairs, with one valve controlling the hot water and the other controlling the cold water.

Shutoff valves allow you to turn off the water supply at the sink, rather than shutting off the water to the whole house. This is especially useful when you need to repair or replace a faucet without disrupting the entire household.

Shutoff valves can be installed onto the water pipes without soldering, thanks to compression fittings. However, you'll need to turn off the water to the house to replace a shutoff valve.

Here are the common types of connectors you'll find on shutoff valves:

A supply tube is a braided wire or plastic mesh tube that supplies water to the bathroom faucet.

It always comes in pairs, one for hot water and one for cold water. These tubes are connected to the bottom of the sink faucet and shutoff valves with attached nuts.

Supply tubes can sometimes fail, and it's not uncommon to have to replace them.

The drain tailpiece is a crucial component of your under sink plumbing. It's the straight section of pipe that connects to the bottom of the sink drain fitting.

Typically, the tailpiece attaches to the drain fitting with a slip nut, a threaded ring that can be tightened and loosened by hand or with channel-lock pliers.

A tapered plastic washer underneath the nut creates a watertight seal, preventing leaks and water damage.

The tailpiece is often connected to a pop-up drain, where the lever rod of the drain assembly connects to a port on the back of the tailpiece.

The drain pipe is a crucial component of under sink plumbing. It carries wastewater from the sink to the main drainage system.

The drain pipe is typically connected to the P-trap, which is a curved drainage pipe under the sink. The P-trap's curve is designed to hold standing water.

The standing water in the P-trap prevents sewer gases from rising from the sink drain. This is especially important to maintain a healthy and odor-free environment.

The drain pipe is usually connected to the home's drain pipe using a P-trap adapter. This adapter typically has a 1-1/2-inch-diameter tube with slip joints.

Here's a breakdown of the key components involved in under sink plumbing: