How to Plumb a Double Bathroom Sink

What You'll Need
Plumbers putty
Tape measure
Plumbers wrench
Saw for metal pipes
Teflon or PTFE tape
1 1/4 -inch drainpipe

In case you live in a crowded house and you have to share the bathroom with a number of other people, the best solution is installing a double bathroom sink so that the crowding can be at least reduced by half. The cheapest and easiest drainpipes for such sinks are made of PVC, but there are also those that are made of brass or steel. The pipes can be left exposed or concealed inside a cabinet.

Please note that the plumber’s wrench, the saw and the PTFE tape need to be used only if the drainpipes installed for the double bathroom sink are brass or steel, not PVC. Sinks in bathrooms usually use 1¼-inch drainpipes, while kitchen sinks use 1½-inch drainpipes. It is important to measure the diameter of the pipe first.

Step 1 – Removing the Old Drainpipe

If you think it is necessary, change the old drainpipe in case it is damaged or worn out. If the old drainpipe is made of brass or metal, take it away with a plumber’s wrench. Each part of the pipe is linked together with slip nuts, remove them with the wrench.

Step 2 – Locating the Drainpipe In the Wall

Find the drainpipe in the wall and check whether it is located between the bowls of the sink, on the left or on the right. This is to be done because according to the location of the drainpipe, you need to install an outlet drainpipe, i.e., directly linked to the P-trap.

Step 3 – Installing the Drains

Install the drains carefully into the holes of each bathroom sink and apply some plumber’s putty to the surface of the sink so that leaking will be prevented. Once the drain is fixed, put away any extra putty left.

Step 4 – Connecting the Ends of the Drains

Connect the ends of the drains with the slip nut onto the tee of the outlet drain. Be sure that the tee is centered to the holes of the double sink.

Step 5 – Measuring the Height between the Wall Drain and the Sink

It is now time to measure the height between the wall drain and the sink. If necessary, trim the extension tube between the P-trap and the outlet tee to match the measured height. In some situations you will not even use an extension tube.

Step 6 – Affixing the Extension Tube

Affix the extension tube to the bottom of the outlet tee and fasten the pipes together with the same slip nut of the extension tube.

The main difference between P-traps and S-traps is that the P-traps are used for wall drains while S-traps are used for floor drains. Make sure to put the base pipe of the extension tube into the trap and secure it properly with the slip nut, then put the trap into the drain and pass the slip nut from the trap to the wall drain.