How to Install a Toilet: Complete Plumbing & Installation Guide

Installing a toilet is one of those DIY projects that seem more daunting than they really are. I can remember walking into a Reece showroom, gazing up at a wall of gleaming new suites, and thinking that I could never install one myself. But if you can follow instructions, operate a spanner, and lift heavy objects without dropping them, you can do it. Learning how to replace a toilet without calling a plumber is definitely worth an afternoon of your time.

Anatomy of a Toilet

It’s helpful to understand the workings of your toilet before you start. There are two main components: the bowl (the bit that sits on the floor) and the cistern (the tank that sits on top or is mounted to the wall). Understanding the key toilet cistern parts will make the process much less confusing.
The cistern contains the toilet flush mechanism, the device that dictates the flow of water from the tank into the bowl when you press the button. This comprises the inlet valve, outlet valve, and overflow tube. A toilet plumbing diagram will show you how the water supply is connected at the bottom of the cistern via a braided hose and how the waste departs via the trap that lies under the bowl.
Knowing this will be the difference between a cool, calm and collected job and a frantic phone call to a tradesperson at 9am on a Saturday morning.

Signs That You Need a New Toilet

Not every problem with your toilet will require a full replacement — a leaking cistern or a faulty flush button can usually be rectified with an inexpensive visit to Bunnings. But sometimes, learning how to replace a toilet is unavoidable.
If you notice any cracks in the porcelain, that’s a sure sign that you need a new toilet. A cracked toilet can leak without you even realising, causing damage to your subfloor and creating mould. If your toilet continues to wobble despite how tightly you tighten the bolts, it may be a sign that the flange has deteriorated. And if your toilet is older and does not feature a dual flush button, you might consider replacing it with a WELS-rated toilet suite, which could reduce your water usage by a third. And let’s not forget aesthetics, if you’re renovating and everything else in your bathroom is new, a stained, dated toilet is going to bring the whole thing down.

What You’ll Need

Before you begin, make sure you have all the necessary materials: an adjustable spanner, a bucket and some old towels (things will get damp), a putty knife, and a new wax ring or rubber gasket seal. Most new toilets will come with mounting bolts, but check to make sure.
Turn off the water supply by locating the isolation tap behind the toilet and turning it. Flush your toilet to empty the cistern and bowl, then use a sponge to soak up as much water as you can.

Removing the Old One

Cut the water supply to the toilet and detach the supply line from the cistern, then remove the plastic caps covering the floor bolts. Take out the bolts and, if rusted, cut them with a hacksaw, taking care not to scratch the tiles. Remove the old toilet by gently rocking it from side to side to break the seal, then lifting the toilet off the floor. Toilets are heavy so it’s best to have someone helping you. Place the old toilet onto a drop sheet. Push a rag down the drain pipe to stop any sewer gases coming into the bathroom. Remove the old wax ring from the flange and examine the condition of the flange, if it’s damaged or rusted you will need to replace it before installing your new toilet, this is probably the best time to consider using a licensed plumber.

Installing the New Toilet

Place the new wax ring onto the flange and sit the bowl onto the mounting bolts. Make sure you push down to ensure the wax ring seals. Use the mounting bolts to secure the bowl to the floor, be careful not to over tighten as you can crack the porcelain. Tighten a little on each side at a time. Before you buy your new toilet you will need to check the set out (the distance from the wall to the centre of the drain) and the trap type. Most Australian houses have a p trap toilet configuration, which has the waste going out through the wall. A pee trap toilet is another term you might see at your local Australian hardware store for this same configuration. If you have an S-trap (the waste goes down into the floor) you will need to ensure the new toilet is an S-trap. Follow the manufacturer’s instructions to attach the cistern to the bowl and reconnect the supply line. Turn the water back on and do a few test flushes to ensure there are no leaks from around the base, the supply line or around the cistern join. If you’re wondering how to replace a toilet so you end up with something that will really enhance your bathroom, you might like to consider a kohler toilet, their toilet suites offer some great designs that will complement any modern or traditional bathroom.