How to install a toilet on the floor: waste pipe, fixing and seals

What you need

• Adjustable spanner and socket spanner
• Drill with an 8 mm masonry or tile bit
• Small spirit level
• Pencil and tape measure
• Scraper or putty knife
• Bucket, sponge and cloths
• Gloves and safety glasses
• Sealant gun
• Toilet with its cistern and seat (Roca Dama-N, Victoria or Meridian; Gala, Sanindusa or Bricodepot)
• 110 mm pan connector for the waste pipe (straight, offset or curved depending on the distance)
• Fixing kit with stainless steel screws, nylon wall plugs and washers
• Cistern gasket, if it is a separate cistern, and a new flexible hose
• PTFE tape or a fibre washer for the flexible hose
• Anti-mould sanitary sealant: Sika, Pattex Baño Sano or Ceys
• Liquid soap or silicone grease to lubricate the seal

Step by step

1. 1

   Measure and choose the right toilet

   Measure from the centre of the waste outlet to the finished wall. For a horizontal outlet it is usually 180 to 200 mm. Also check whether the waste pipe comes out of the wall or the floor: each case needs a different toilet. If the distance does not match, an offset or curved pan connector corrects it.

2. 2

   Turn off the water and disconnect the cistern

   Close the angle valve (stopcock), flush to empty the cistern and dry the bottom with a sponge. Unscrew the flexible hose with the adjustable spanner and keep a bucket underneath. If the cistern is separate, that comes off too.

3. 3

   Remove the old toilet

   Take off the caps covering the fixing screws. If they are rusty, apply a little penetrating oil and wait ten minutes. Rock the toilet from side to side to break the seal and lift it with a second person, because it weighs between 20 and 30 kg. Plug the waste pipe straight away with a thick cloth to stop the smell and keep anything falling in.

4. 4

   Clean the waste pipe and the floor

   Scrape off any remains of putty, cement or sealant. Check that the pipe is whole, with no cracks, and that the floor is flat. If there is an unevenness of more than 3 mm, or the pipe is lead or fibre cement, stop and call a plumber.

5. 5

   Dry-fit and mark the fixings

   Place the toilet over the waste pipe without gluing anything, with the base resting on the floor. Check that it sits straight and at the right distance from the wall. Mark the inside of the fixing holes with a pencil.

6. 6

   Drill the fixing points

   Move the toilet aside. Drill with the 8 mm bit at low speed and without hammer action on tile, to the depth of the plug. Before drilling, confirm there is no underfloor heating or pipework below. Push in the plugs.

7. 7

   Fit the pan connector and seal

   Lubricate the connector with liquid soap and push it into the waste pipe to the bottom. With a horizontal outlet, the connector is placed on the toilet outlet and pushed home in one go. Check that it is not bent or cut.

8. 8

   Bed the toilet down and screw it in

   Press the toilet onto the connector until it sits down. Fit the washers and screws and tighten each one a little, alternating between them. Finish with a quarter turn more. If you tighten fully, the ceramic cracks.

9. 9

   Connect the cistern and the water

   If the cistern is separate, fit the gasket and bolts with the rubber washers. Connect the new flexible hose to the angle valve, with PTFE tape on the threads that need it. Open the water slowly.

10. 10

    Test and check for leaks

    Let the cistern fill and flush five times. Run dry tissue paper around the cistern joint and the base. If there is damp, take it apart and check the connector, which is the weak point.

11. 11

    Seal the perimeter

    Put masking tape on either side of the base and run a thin bead of anti-mould sanitary sealant. Leave a small gap at the back so any future leak will show. Avoid using it for the next 12-24 hours.

Before you buy: type of waste pipe and distance to the wall

The most expensive mistake when installing a toilet is buying without measuring. There are three configurations: a horizontal outlet (the waste pipe comes out of the wall), a vertical outlet (it comes out of the floor) and a dual outlet (it adapts to both). The dual outlet is the most versatile if you are not sure about the waste pipe, because it connects with different pan connectors.

Measure the diameter of the pipe too: in modern homes it is usually 110 mm. In older buildings in Valencia or Alicante you may find lead pipe, fibre cement or other diameters, and then the set-up needs specific adaptors or a plumber's inspection.

How to install a toilet on the floor: the three seals that matter

A properly installed toilet has three seals. The first is the connection to the waste pipe: the connector or seal that prevents smells and grey water leaks. If it fails, you will notice a bad smell and marks on the floor. The second is the fixing to the floor: the screws and plugs that stop the toilet moving. The third is the connection to the cistern, which on a close-coupled toilet comes from the factory and on a separate-cistern toilet needs its own gasket.

Manufacturers (Roca, Gala, Sanindusa) include a fitting sheet with the measurements for each model. Keep it: it gives the tightening torque and the fixing points, and saves you drilling in the wrong place.

If during the job you find that the cistern mechanism is worn, take the chance to replace it. We explain how in how to replace a toilet cistern and in toilet cistern keeps running.

Common mistakes when installing a toilet

• Gluing the toilet down with sealant instead of fixing it. Sealant is no substitute for screws. Within weeks it moves and the waste pipe seal gives way.
• Tightening the screws fully. The ceramic cracks and the damage cannot be repaired: you have to buy another toilet.
• Not lubricating the pan connector. The rubber creases and the seal sits badly. Use liquid soap or silicone grease.
• Reusing the old flexible hose. It is a €4-10 part and the most typical leak after a toilet replacement.
• Drilling without knowing what is underneath. In flats with underfloor heating, drilling into a pipe floods the floor. Ask the residents' association (comunidad de vecinos) or the developer.
• Not testing the flush five times. A slow leak does not show on the first flush; it appears after a few.

When to call a plumber to install the toilet

Installing a toilet onto a waste pipe in good condition is a job done at home with basic tools. What we do not do, and a handyman should not do, is create a new waste pipe, move the outlet, change sections of soil stack or break up the floor. That is building work, it affects the residents' association and may require a licence or permit.

At Manitas Costa, replacing a toilet costs €90-150 labour, not counting the toilet. If you would rather we supplied the toilet, we sort it out beforehand by WhatsApp. We arrive in 20-45 minutes in Valencia, Alicante, Torrevieja and Benidorm. We give a fixed price, an invoice including IVA (VAT) and a six-month written guarantee on labour.

You can see the details in plumber in Valencia and Alicante and plumber prices. For specific areas, plumber in Valencia and plumber in Alicante. If you are also refurbishing the bathroom and replacing the bath, see how to fit a resin shower tray.

Installing a toilet on the coast: salt air, empty homes and limescale

On the coast, ordinary steel screws rust within a few years, especially in seafront homes in Torrevieja, Benidorm or Villajoyosa. Buy stainless steel screws and plastic caps. If the property is a second home and stays shut for months, the toilet trap can dry out: flush when you arrive and let the water run for a minute so the water seal returns.

With hard water, limescale builds up on the rim and in the cistern. Avoid problems from day one with a monthly vinegar clean, and see how to remove limescale from a toilet if it has already formed. Glazed ceramic toilets cope well with vinegar, but never mix bleach with acid products.