Installing and Connecting a Close-Coupled WC

The job follows a clear order, and each step depends on the one before it. A mistake at the start often only shows up at the first flush.

1. When replacing an old toilet, the water is turned off, the cistern drained, the supply hose disconnected and the old pan unscrewed and lifted out.
2. The area is cleaned of old silicone, putty and dirt, and the soil pipe is checked to make sure it is clear and undamaged.
3. A new pan connector is fitted into the soil pipe. The pan is set in place, levelled with a spirit level, and the fixing holes are marked.
4. Holes are drilled, wall plugs inserted and the pan is screwed down evenly on both sides.
5. The cistern is fitted onto the pan with its seal and tightened.
6. A flexible connector hose is attached to the isolating valve, the cistern is filled and the float is adjusted.
7. The flush and all joints are tested for leaks, and finally a bead of silicone is run around the base of the pan.

Before you buy a new WC, look at where your soil pipe comes out. This is the single most important piece of information for the whole job.

• A horizontal outlet comes out of the wall and is the most common type today. The pan connects to it with a rubber connector or a bend, and pans for it are often called P-trap pans
• A vertical outlet goes straight down into the floor. It is more common in older houses, and the pan sits directly above the opening. These pans are often called S-trap pans
• An angled outlet is less common and needs a pan or connector designed for it

If you buy a pan with a different outlet from the one you have, an offset pan connector or bend often solves the problem. If the soil pipe itself has to be moved, you are looking at cutting into the wall or floor and repairing the tiles. In a block of flats this can reach the communal soil stack, so talk to the building management or owners' association first. If the work grows into a larger building alteration, check with your local building authority what you need.

When choosing a new WC, it is worth looking at a dual flush (the two volumes depend on the model), a quieter fill valve and a rimless pan, which is easier to clean.

The simplest case is a like-for-like swap: the same outlet type, level tiles and a working isolating valve. The installation is then quick and without surprises.

The job takes longer and costs more mainly when there is:

• An outlet in a different position or direction from what the new pan needs
• An old cast iron soil pipe with hardened putty or mortar that is hard to clean out
• Uneven or cracked floor tiles under the pan
• A rusty or leaking isolating valve that needs replacing. In a flat this often means shutting off water to the whole flat or the riser
• Underfloor heating or pipes in the floor, which require careful, precise drilling
• New wall and floor tiling being done at the same time as the toilet

If the bathroom is being retiled, the WC is fitted only once the floor tiles are finished. The pan then stands on a flat surface and nothing has to be cut around it.

If you are replacing a WC with a model that has the same outlet and you do not need to alter any pipework, you can do it yourself. You will need a spirit level, a drill with tile and masonry bits, a screwdriver, a spanner, sanitary silicone, and a bucket with a cloth.

1. Close the isolating valve, flush, and soak up any remaining water from the cistern and the pan.
2. Disconnect the supply hose, unscrew the old pan and carefully pull it out of the soil pipe.
3. Cover the soil pipe temporarily with a cloth to stop smells and to keep anything from falling in.
4. Clean the floor and the pipe opening of old silicone and putty.
5. Fit the new pan connector into the soil pipe and set the pan in place as a dry run.
6. Level the pan in both directions with a spirit level and mark the fixing holes with a pencil.
7. Put masking tape over the drilling points, drill the tile without hammer action using a tile bit, and switch on hammer action only once you reach the concrete.
8. Insert the wall plugs, push the pan onto the connector and tighten the screws alternately, only until the pan sits firmly.
9. Fit the cistern with its seal and tighten the bolts evenly, without forcing the ceramic.
10. Connect the flexible hose to the valve and the cistern, first by hand, then gently with a spanner.
11. Open the valve slowly, let the cistern fill and check every joint with a dry paper towel.
12. Flush several times and watch for water at the outlet or under the cistern.
13. Seal around the base of the pan with sanitary silicone and let it cure as the manufacturer specifies.

If it turns out the soil pipe has to be moved, or the isolating valve will not close, leave the job to a plumber.

In practice the problem often does not appear straight away but after a few weeks of use. The usual causes are:

• Screws or bolts overtightened, which sooner or later crack the ceramic of the pan or cistern
• A pan not levelled properly, so it rocks and gradually loosens the seal at the outlet
• An old or badly fitted pan connector that seeps water and smells when you flush
• PTFE tape on hose joints that are sealed by a rubber washer. The tape does not belong there and can cause a leak
• A kinked or unnecessarily long supply hose
• Drilling straight into tiles with hammer action, which cracks them
• Drilling without checking whether heating pipes or other services run in the floor

When applying silicone around the base, some fitters leave a small unsealed gap at the back. If the outlet ever starts to leak, the water then shows up at the front instead of seeping unseen under the pan for years.

When the job is handed over, ask to see everything working. The check takes a few minutes and avoids arguments later.

• The pan stands level and does not rock when you push it sideways by hand
• The ceramic has no cracks, especially around the fixings
• The outlet and the floor under the pan stay dry after several flushes
• The joint between cistern and pan does not seep during flushing
• The hose is not kinked and its joints are dry
• The isolating valve opens and closes easily
• The cistern fills and the valve then stops the water completely, with nothing trickling into the pan
• Both the small and the full flush clear the pan in one go
• The silicone is continuous and smooth, and the area has been cleaned