How To Connect A New Toilet To An Existing Soil Pipe

  • Learn how to connect your new toilet to the soil pipe you already have fitted at home.
  • Find out more about soil pipes.

Unless it’s in disrepair, there are very few reasons that you would need to replace your soil pipe when putting in a new toilet. Connecting a new toilet to an existing pipe couldn’t be easier!

What is a soil pipe?

The soil pipe in your bathroom carries the dirty water from the flushes of your toilet system from your home to the sewer. It doesn’t just link up to your toilet, either! If you have any urinals or bidets in your home, these are connected to the soil pipe, as well.

In commercial properties, it’s the same. All bathrooms and water closets have soil pipes to carry away water that has been soiled with waste.

A soil pipe should not be confused with a waste pipe. While a soil pipe takes away the water from humans doing their business, a waste pipe carries away water from your bath, shower, sink, and washing machine.

Toilet to soil pipe
A sewer pipe being fitted underground.

Where can I find the soil pipe?

There are two places that your soil pipe should be on your property. It’s either going to be above your roof, or it’s going to be on the side of your property.

Older house owners will find a cast iron pipe on their roof, which is their soil pipe. But more modern properties should have a very standard and plain-looking plastic pipe on the side of their home that branches out from the building.

These are not large pipes, nor are they particularly long. You’re looking for a short pipe that has a bit of a bend (like an elbow shape) or one that stands upright but has a couple of different openings connecting to other pipes.

How to connect your new toilet

Before you get started, make sure that you’re not fitting a second toilet on the same horizontal section as your other toilet (if you can help it, otherwise just make sure there’s a good amount of distance between the toilet and the soil pipe).

The last thing you need is someone to flush one side and have that affect the other toilet from across your house. The siphoning effect would be so loud! …And if someone is using the other toilet at the same time, just imagine their confusion.

So, to connect your new toilet (if it’s a second toilet), you’re going to need to play around a bit.

First, get the measurements for your new toilet’s Y and then measure and cut your soil pipe so that this will fit nicely.

Next, add a slip coupling to your soil pipe at the end where the main stack is.

Then connect the Y on the opposite end (by the new toilet) using a push fit connection.

There’s a lot of back and forth during this process, but you’re almost there!

See Also
loft joists

Your final step is to slide the slip coupler up so that it connects the soil pipe to the new toilet’s Y. Once you’ve done that, seal both ends with more slip couplings.

If that sounds complicated or you aren’t really sure what you’re doing, we would highly recommend hiring a professional, licensed, and trained plumber to come and do this for you.

Connecting up a new toilet when it’s the only toilet in the house is a lot easier and doesn’t require half of the steps that we’ve just laid out for you. A replacement toilet will only need to be re-fitted where your old toilet was. Everything is already in place and ready to go!

New toilet pipe
A toilet in a modern bathroom.

Why hire a plumber

Because of the potential mistakes. That’s the first thing that comes to mind while looking over the steps of this household procedure. If you aren’t used to putting in the plumbing for your own home, it’s best not to start with something complicated like fitting a second bathroom or ensuite toilet.

A professional plumber will be able to tell you upfront if they have experience fitting new toilets onto existing soil pipes. If they do, great! If they don’t, at least they’re honest about it and you can move on and find someone who does know how to pull off the fitting.

Plus, with a professional, there’s less chance of damage to your home or your new plumbing.

© 2022 All Rights Reserved.