Bathroom Design – Working With Soil Pipes

One of the trickier aspects of bathroom design is working with soil pipes in small bathrooms.

The soil pipe is the large pipe that ducts toilet water out of the bathroom. Usually made from plastic these are very large and their position will be determined by your outside drainage.

Sometimes these pipes run vertically down through the house internally. Sometimes they run down the outside of the building (as is the case in our diagram). Moving them is not an easy job in most circumstances. They are usually the main factor that limits your ability to move things around to exactly where you want them.

So what are the options if it is limiting your desire to remodel your bathroom the way that you want to?


A Typical Small Bathroom Layout

In the diagram you see a typical small bathroom layout. The bath runs along one wall but the soil pipe (shown in red) prevents it being fitted flush up to the wall that the toilet is fitted to.

The worst option in this situation is also the one that most people adopt. They build a flat shelf at the end of the bath to fill the gap. And then tile it.

If they also have a shower over the bath then this solution is just one big problem waiting to happen.

Grout (and tiles themselves) are very brittle and will crack if there is too much movement. As the end of the bath that meets the tiles is not attached to anything other than a wooden frame it is liable to move slightly in use. This leads to cracks in the grout which then leads to leaks.

Siting the shower at the other end of the bath will help keep the majority of the shower spray away from the horizontal tiled area but it is still problematic. Water will settle on the tile surface. The grout will absorb the moisture and mould will start to grow. So what other options are there?

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Moving The Wall

This in not quite as dramatic as it sounds.

In the diagram above it would simply involve making a small stud-wall from timer and plywood to fill in the gap at the end of the bath.

If you are tiling the wall use plasterboard. Do not use plywood as it expands and contracts at a different rate to the tiles. The adhesive will loosen over time and the tiles will work loose.

Better still use bathroom wall panels instead of tiles as these can be fitted over any sub-surface and are totally waterproof.

The difference with this option is that it runs floor to ceiling and any tiling will be vertical so water will run off.

This solution also gives you the option to bury pipework for the shower making the whole job look neater. If the shower is at the other end of the bath (as in this case shown in the photo) you can build niches into the wall which look great. They also offer practical storage which is usually in short supply around a shower area. If you fit lighting into the niches they look even better.

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Moving The Soil Pipe

Modern soil pipes have a push-fit mechanism that utilises a rubber seal. On internal soil pipes there will be a T junction in the room that accepts the horizontal output pipe from the toilet. It is usually (but not always) possible to pivot this T Junction enabling the toilet to be fitted on a different wall.

If the soil pipe exits through the bathroom wall then this option will not be available. There might be an option to re-route the pipe inside the bathroom but this will very much depend on many factors.

Moving or re-routing a soil pipe is not an easy task so should really be left to the professionals.