Adding a toilet to existing plumbing: A step by step guide

A lot of people want to add another toilet to their house. There are 2 main things that need to happen when you want to add a toilet: having a water supply and being able to remove the dirty water.

 Is this easy to do? Let’s explore it.


1/ Adding a water supply line

Depending on the type of pipes you have, this might be easy or quite hard to do. Most people have copper or PEX lines and it is quite straightforward to add another water line. Adding a steel pipe can be more work. 

For copper, you can often add a T piece that diverts the water to the toilet. Just keep in mind that water pressure is important and check if this doesn’t lead to issues. Toilets don’t need a constant water supply so generally, it shouldn’t be too much of a problem. You can weld copper or add a push fitting to install the new supply pipe.

For PEX, we can often run a pipe from the manifold. It is easy if we can do this under the floor. Sometimes we can run the pipe over the wall or from the ceiling as well. Finding a way to make it look nice without breaking open a wall or pipe can be challenging. In some instances, we can add a T piece to an existing pipe as well. 

In most instances, it is quite easy to install a water supply line for the toilet. If there is no pipe nearby, it can be more work but it is often feasible to do this if there is enough water pressure. In some instances, you will have to add a pump to get the water to the toilet.

2/ Adding the drain

Adding the drain can be more challenging. The drain has to be at a certain angle to make sure that the water flows properly. If there is no drain nearby, it can be difficult to connect it to the mainline. Especially if the toilet is upstairs, it can take some work to make sure that the drain isn’t an eyesore. The plumber will have to figure out how to run the drain.

It is also important that the drain that gets connected to the toilet is wide enough so that you don’t have clogs. Plumbers often have to do some math to make sure that everything works out fine. 

Finding a way to connect the drain to the main drain is often the biggest challenge. It is not always allowed to mix the drain of the toilet with the drain of the shower or sink. In some locations, they have to be separated so that it is easier to process the water. Check your local plumbing code to make sure that you know what is required.

3/ Installing the toilet

Once you have determined how the drain will run, it is possible to install the toilet. The first step is to add an opening to the floor. You have to install the drains, flange, and wax ring. Often PVC drains are used for toilets. This is glued so that the drains fit well together. Make sure that the angle of the drain is correct.

You will have to add a T piece to the main drain so that the water can flow into it. This is done by cutting the drain open and gluing the T piece in place. Then we can add the drain that runs to the toilet. It is important that you let the PVC glue cure long enough. The weather affects how long you have to let it dry so check the manual to make sure that you are doing it correctly. Drain leaks can be nasty and should be avoided at all costs.

Once everything is installed, we can add the toilet. Make sure that you don’t overtighten the bolts as some toilets are not able to handle a lot of pressure. 

In some instances, an inspector has to sign off on the new installation. It can be a great idea to contact this person in advance to see if they approve of your design. If you have a septic system, they might want to make sure that your system can handle the output of your plumbing installation. They might take a look at the capacity of your tank to decide if a new toilet can be added.

To conclude, we can state that it is not always easy to add a new toilet. You have to look at your current installation and see how it can be added. You have to take water pressure, the angle, and the size of the drains into account.

This makes sure that you don’t have clogs or low water pressure. Plumbers have to take a lot of things into account when installing a new toilet and it is not always easy to do. Especially the drain can be a challenge as it is not always easy to hide it. You can add some drywall to do this but it can make another room smaller. You have to think about the installation before you start. In some instances, it can be a great idea to change the floor plan so that it is easier to run the drain to the main sewer line.

If you have to add a pump to increase the water pressure and run the drain over a big distance, the project will cost a lot more. You have to think about your budget and what is really needed. Longer drains can cause more problems as well. T

his project might be too hard for a DIY’er as there are several things to take into account and an error can create issues with your plumbing system. It can also make it harder to sell the house as the house inspector might remark that there are issues with the plumbing system. 

A lot of planning is required to install a new toilet. You can’t just install it in any room as you need to take the connections with the water supply and drainage system into account. For this reason, it is important to study the house and the plumbing system if you want to add a new toilet.