How to Install a Toilet: A Step-by-Step Expert Guide

Whether you’re embarking on a full bathroom renovation or simply updating an old, inefficient fixture, learning how to install a new toilet is a rewarding project that can save you a significant amount of money on labour costs.

At Build & Plumb, we know that plumbing projects can feel a bit daunting. However, with the right tools and a bit of “know-how”, fitting a toilet is a task that most confident DIYers can tackle in an afternoon. In this guide, we’ll walk you through the process from start to finish, ensuring your new installation is leak-free and built to last.

How much to install a toilet?

Before you pick up your wrench, you might be wondering about the costs. If you were to hire a professional plumber, the average price for installing a toilet in the UK typically ranges between £100 and £250, depending on your location and the complexity of the plumbing. By learning how to install a toilet yourself, you can put that budget towards higher-quality fixtures or that designer towel rail you’ve had your eye on.

The Essentials: What You’ll Need

Success in plumbing starts with having the right gear. To fit a toilet properly, make sure you have the following to hand:

• A new close-coupled toilet (The most common and easiest type to install).
• Flexible pan connector.
• Adjustable wrench and spanners.
• Spirit level (Essential for a professional finish).
• Multi-purpose drill and masonry bits.
• Sanitary silicone sealant and a sealant gun.
• PTFE tape.

Step 1: Preparation is Key

Before you remove your old toilet, always inspect your new one for any cracks or chips. There’s nothing worse than getting halfway through a job only to find a defect.

Top Tip: Turn off the water supply at the isolation valve (usually located on the pipe leading to the cistern). If you don’t have one, you’ll need to turn off the mains stopcock. Flush the old toilet to empty the cistern and use an old sponge to soak up any remaining water.

Step 2: Assemble the Cistern

Most modern toilets come with the internal flush mechanism separately. Follow the manufacturer’s instructions to fit the flush and fill valves inside the cistern.

• Don’t over-tighten: Hand-tightening is usually enough for the plastic nuts; over-doing it can crack the ceramic or perish the rubber seals.
• Place the large rubber doughnut washer over the base of the flush valve, where the cistern meets the pan.

Step 3: Fit the Cistern to the Pan

Lift the cistern and align it with the holes on the back of the toilet pan. Insert the long connecting bolts (with their washers) through the cistern and pan. Secure them underneath with the wing nuts provided. Use your spirit level here to ensure the cistern is sitting perfectly straight.

Step 4: Position and Connect the Waste

Slide your flexible pan connector onto the back of the toilet outlet. A small amount of silicone grease or even a bit of liquid soap can help the rubber seal slide on easily. Push the toilet into its final position, ensuring the connector fits securely into the soil pipe.

Step 5: Secure the Toilet to the Floor

Once you’re happy with the position, mark the fixing holes on the floor with a pencil. Move the toilet aside, drill your pilot holes (use masonry bits for tiled or concrete floors), and insert your wall plugs. Reposition the toilet and screw it into place. 

Build & Plumb Advice: Never overtighten floor screws, as the pressure can easily crack the porcelain base.

Step 6: Connect the Water Supply

Connect your cold water supply pipe to the cistern’s inlet valve. We recommend using a flexible waste connector if your pipework doesn’t align perfectly. Wrap a little PTFE tape around the threads to ensure a watertight seal.

Step 7: The Final Flourish

Turn the water back on and let the cistern fill. Flush the toilet several times and check each joint, the cistern bolts, the water inlet, and the floor for any signs of moisture. 

Finally, run a neat bead of anti-mould silicone sealant around the base of the pan, where it meets the floor. This provides extra stability and a professional, hygienic finish.

Ready to start your project?

Now that you know how to fit a toilet, it’s time to get to work! At Build & Plumb, we stock everything from luxury toilets to the essential plumbing tools you need to get the job done right.

For more expert advice and inspiration for your next home improvement, contact our team today!