Finished basement toilet plumbing: Step by Step overview

You’ve got the upstairs bathroom all finished and looking great, but now you’ve got to tackle the downstairs half of the house. What do you do? You plumb your unfinished basement!

For most homeowners, tackling the basement is often the last frontier of home DIY projects. But once you get started, it’s not that hard to get done. In fact, with some basic plumbing knowledge and a little elbow grease, it’s not too hard to re-plumb an unfinished basement bathroom.


With the right tools, a little know-how, and a little bit of cash, you can have your finished basement bathroom in no time. Read on for a step-by-step guide to plumbing an unfinished basement bathroom, from start to finish.

Get the required permits for the basement toilet

Before you begin any plumbing project, you’ll want to make sure you have the necessary permits. Check with your local government to make sure that you have everything that is needed.

Choose the plumbing supplies

You’ll need the right tools for the job, of course, and the right kind of pipe to run water through. When buying plumbing supplies, keep in mind that you’ll be running water through these pipes for a while. You don’t want any leaks, so choose high-quality pipe and fittings.

PEX is often used for water supply. PEX-A is often the best option as it makes sure that the water pressure is high enough. PEX-B can have issues with this. PVC is generally used for drains. Make sure that you use the right diameters for the pipes and drains. 

You also might need a plumbing riser to make sure that the drains come up high enough.

Layout the water drains

Before you can put in the water supply pipes, you’ll have to get all the water drains in the right position. PVC pipes are generally glued together. Check the curing times on the packaging as the weather affects this. It is important that you glue the drains well as fittings can be weak points that lead to leaks. Also, make sure that you use the right slope for the drains. This avoids clogs.

The toilet drain often can’t be connected with the drains of the sink and shower. This is a different type of water and it often has to be collected in different drains. You can connect the shower and sink drains together by adding a T piece. These drains can then be connected to the main sewer line. Don’t forget to add an air valve so that air can push the water down. 

You can use software to make a scheme of what needs to happen. It is handy to have this. If you need to work in this area later on you know where the drains are. It can also help you to buy the right tools and fittings. Having to go to the hardware store a lot costs a lot of time. If you have everything at once, you don’t have to stop to get more items. 

Install the water supply pipes

Once you’ve marked out the water drain lines, it’s time to get the water supply pipes in. The water supply line runs from the main water supply, usually beside a wall. PEX is quite easy to install. Just make sure that you have a manifold nearby and connect the pipes to it.

 If you plan to add a heater, you should install this first. There should be no air in these pipes so they should be as flat as possible. Once this is done, you can work on the water supply lines. Don’t forget to close them with some tape so that no dirt gets into them.

Get the toilet and sink ready

Once the drains are done, we can start to add the toilet flange. Once this is done, we can start to install the toilet itself. This is quite straightforward. Just make sure that the toilet is hanging level and that you don’t overtighten the bolts. In newer toilets, you can select how much water is used per flush. Don’t use too little water as this can lead to clogs. You might have to add a pump to get the dirty water upstairs if the toilet is below grade. This costs more money to install but is sometimes needed.

If you’re planning on running the plumbing for the tub or showerhead through an exterior wall, you’ll want to get the rough plumbing ready. This means cutting holes in the exterior wall and running the pipes through them.

You’ll need an exterior hole for each exterior pipe that will bring water to the bathroom. Bore out the hole with a hammer or a nail gun, then cut the pipe to length and install the tee fitting. A tee fitting is a one-piece fitting that has two openings: one for water, and one for waste.

 Use enough clamps so that the drains won’t sag over time. This can break the drains. Drains can weigh quite a lot so they need enough support. 

Adding a sink is quite easy as well To determine where we have to drill the holes to hang the sink, we are going to use a trick. You can place the sink on the floor and measure how high it should get. Then draw a circle in the hanging holes. Measure the holes to see how high they have to be. This allows us to determine how high we have to drill the holes to get the sink at the desired height. Once the sink has been installed, we can add the drains. Once this is done, we can add the water supply and test the sink. You can finish things by adding some chalk around them. This makes it easier to clean the sink and shower.

Make sure that everything conforms to your local code. An inspector will often check your work. If there is an issue, it can affect the value of your home so make sure that everything is done correctly. You can always hire a plumber to do some of the work if you don’t know how to do it.

 To conclude, installing a basement bathroom is quite straightforward if you have done some planning. If you know how to glue PVC and install PEX, it is quite straightforward to get it done. It is essential that you use the right diameter and angle when you install the PVC drains. Some companies offer kits that give you all the gear that you need. This makes it easy to install everything on your own.