How to Fit a Toilet: Complete Installation Guide

Toilets seem simple - it's just a pan connected to a waste pipe and a cistern connected to water. But there are plenty of ways to get it wrong. Here's how to fit one properly.

Removing the Old Toilet

If you're replacing an existing toilet:

1. Turn off water supply (isolation valve or mains)
2. Flush toilet to empty cistern
3. Disconnect water supply from cistern
4. Unbolt cistern from pan (or disconnect close-couple bolts)
5. Unbolt pan from floor
6. Stuff a rag in the waste pipe to block smells

Old toilets can be sealed to the floor with silicone, screwed through plastic covers, or cemented on older installations. You might need to chip away old sealant or cement.

Checking the Setup

Before fitting the new toilet, check:

• Where's the waste pipe? (rear, floor, offset)
• What size is the waste connection?
• Where's the water supply?
• Is the floor level?

Most modern toilets are designed for floor waste (going straight down) or rear waste (going into the wall). Make sure your new toilet matches your waste position, or get the right connector to adapt.

Waste Connections

Straight connector: When the toilet outlet lines up perfectly with the soil pipe.

Offset connector: When there's a slight misalignment. Pan connectors come in various offset amounts.

Flexible connector: For awkward situations. These flex to accommodate different positions but are more likely to block than rigid connectors.

Push the connector onto the soil pipe first, then fit the toilet pan to it. Apply silicone lubricant to the seals if they're tight.

Positioning the Pan

1. Connect pan to waste connector
2. Push back against wall to set final position
3. Check it's level side to side
4. Check it's level front to back
5. Mark fixing hole positions through the pan mounting holes

If the floor isn't level, you'll need to pack underneath or bed the pan on silicone. Don't over-tighten fixings on an unlevel floor - you'll crack the pan.

Fixing to the Floor

For solid floors:

1. Drill pilot holes at marked positions
2. Insert wall plugs
3. Offer up pan and drive screws through mounting holes
4. Don't overtighten - you'll crack the ceramic

For timber floors:

• Screw directly into joists if possible
• Or use toggle fixings if joists aren't in the right place

Cover the screw heads with the plastic caps provided.

Fitting the Cistern

Close-coupled cisterns (sit directly on the pan):

1. Fit the rubber seal between cistern and pan
2. Insert connecting bolts through cistern
3. Lower cistern onto pan
4. Tighten bolts evenly - don't overtighten
5. Cistern should sit level and firm

Low-level or high-level cisterns:

1. Fix cistern to wall at marked position
2. Connect flush pipe between cistern and pan
3. Ensure flush pipe has correct fall

Water Connection

Most modern cisterns use a bottom-entry or side-entry fill valve with a flexible connector:

1. Fit fill valve to cistern (follows manufacturer instructions)
2. Connect flexible tap connector from isolation valve to fill valve
3. Turn on water
4. Check for leaks
5. Adjust fill level if needed

Testing

Before calling it done:

• Fill cistern and check flush operation
• Flush several times
• Check all connections for leaks
• Check pan-to-floor seal (silicone if needed)
• Check it feels solid - no rocking

Common Mistakes

• Overtightening fixings (cracks pan)
• Wrong pan connector for the waste position
• Not checking level before fixing
• Poor seal between cistern and pan (leaks)
• Not testing properly before leaving

A properly fitted toilet should feel solid, flush completely, refill correctly, and have no leaks anywhere. Take time to check everything before you leave.