Shower Waste Fall & Other Basics

Bathroom plumbing is a fun little project. Okay, well, for some people, it’s fun. For others, though, it can be a real hassle. There are all sorts of factors to take into account, and one of our focuses today is going to be shower waste fall. Primarily – how much does it need, and how is it supposed to be done? Don’t worry, those questions will all be answered momentarily, so stay with me.

Shower waste fall needs to be installed with a downward slope. There must be at least 10mm of fall for every 4m of pipe, otherwise, you risk insufficient fall beneath your shower or bath.

There’s a reason for that, but what? There’s only one way to find out – keep reading.

What is Shower Waste Fall?

In short, the fall in a pipe is the vertical amount that the pipe drops over a specific distance. While this term applies to a few things, it’s most commonly applied to shower and bath piping.

The ideal drain slope is roughly 18 mm per metre. It should be dropping no more than the ideal 18 mm slope, otherwise, you’ll end up with a couple of issues:

  1. Clogs – This is the most common issue that you’re trying to avoid. An overly-sloped pipe can clog because liquids move too fast, leaving the solids behind. An under-sloped pipe will also clog, but for the opposite reason.
  2. Cost – If you’re left with imporper slope, you’ll need to fix it at some point. That means you’ll either be left constantly treating it with drain cleaner, or paying a plumber to come out. The former will corrode your pipes, while the latter just costs a lot of money!

Things to Prepare for When Installing Shower Plumbing

While shower waste fall is important, it’s not the only thing you’ll need to plan for. If you’re planning on doing a DIY shower installation, you’ll need to keep the following in mind.

Pipe Size Differences

This is super common in old houses. In the 1970s, the UK switched its standard measurement system from imperial to metric. This means that you could be digging into your plumbing with your new pipes, only to discover an issue. You bought 15 or 22 mm pipes, and the plumbing in your home is measured in .5″ and .75″ instead.

While this can be frustrating, you can purchase adaptors to help out. After all – you’re not the first person to be in this bind. And it’s obviously less than ideal to have to rip out and reinstall a massive section of plumbing. So perhaps the most helpful advice I can give is the following:

Check your home’s plumbing before buying new pipes. Know what sizes you’re working with, or risk a very serious disappointment.

Tight Spaces

While it can be a very frustrating discovery, you may find that there was further work done over your shower. It could be plumbing from other sections of the home or wiring, but either way, it’s trouble. You don’t want to try and work around these things. That means you’ll likely need to remove the shower base to get your work done.

Don’t try to cut corners here. A single slip up with your water pump pliers could spell damage to other parts of your home. You’re trying to install something new, not create more work for yourself.

In other words, don’t take the easiest path, but the safest. You’ll thank me later.

Prepare for Cuts

It’s pretty much unavoidable. Installing a shower or its plumbing will 9 times out of 10 result in needing to cut out parts of your plaster. Whether it’s a ceiling or wall, don’t expect to get out of this without at least a little plastering.

If you’re just replacing the shower drain and base, you can ignore this section (thankfully). Just begin by pulling the old shower pan and drain. Connect the body of the new drain to its new base, and set it in place. Keep in mind, however, that this is a fine balancing act. That means that you’ll want at least one more person to help out here.

Replacing the Trap

In many cases, when installing a new shower trap, you’ll have a welded connection (or three). You’re going to have to remove the old drain, we know that – but it may be better to replace the whole thing.

Depending on how talented you are with plumbing, this can be gotten around. But if you’re new to plumbing, it may be in your best interest to replace the entire drain trap. This will prevent you from screwing up any connections and be generally easier overall.

Final Thoughts

There was a lot of information there involved with shower basics. Don’t worry if you’re feeling a bit overwhelmed – this is a big project. When installing a shower waste fall, it’s vital that you get it properly set. If you don’t, you risk clogs due to either too much or too little slope. The general rule of thumb is that you should have an 18 mm slope for every metre of pipe. Don’t try to get fancy here – just trust the standards.

Beyond that, there are a few things to keep in mind when installing a shower (or part of one) as an amateur. First things first, you’re going to be cutting into plaster here – it’s just bound to happen. Don’t stress too much about that, just do it carefully and with intention (so no willy-nilly cutting). When replacing the drain trap, it’s often better to replace the whole thing than to try and work around welded connections. And finally, be aware of small spaces. It’s not uncommon for further wiring or plumbing to be put around a shower after it’s installed. While this is easy for installation, it makes a pain when trying to work around it later.

Perhaps most importantly, though, is the place where you live. Keep in mind that different locations vary on their standard plumbing, meaning an Irishman and a Brit will have slightly different pipe sizes – which can make a big difference. And as always, please, call a professional if you feel out of your depth here. Plumbing takes specific knowledge to do properly, and they have it – even if you don’t.

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About the Author Harry Thompson

Involved in home renovations throughout his life, Harry is an expert in everything to do with home and garden DIY. In his spare time, he enjoys cooking and tending to his garden.