The waste pipes and trap

Before choosing a shower enclosure, you need to work out how you are going to run the drainage pipes, and check how much height you need under the tray for the pipework. You may be able to cut a hole in the floor to install the waste pipe. If so, you will also need to make an access hatch: either extend the hole for the waste trap beyond where the outside edge of the shower tray will be; or make a separate hatch nearby, within reach of the trap. If your floor is solid, or you cannot achieve enough of a fall for drainage under a suspended floor, you could opt for an enclosure with a step up to the tray; or you could raise the tray above floor level by installing it on a plinth.

If you don’t have enough space under the shower tray to fit a shallow P-trap, you could fit a compact trap. This is specially designed to give the necessary water seal while being shallow enough to fit under most modern shower trays. It has a removable grid for easy cleaning.

Fitting the shower tray

Once the waste pipework is prepared, you are ready to install the shower tray and connect its waste outlet to the trap. Read the manufacturer’s installation instructions too, since different designs may be fitted in slightly different ways.

1. Hold the tray on its side and run a bead of sanitary silicone sealant around the waste hole.

2. Insert the waste outlet into the hole, so that it sits into the sealant. Make sure that you have fitted any washers supplied, and screw on the locking nut using an adjustable spanner. Fit the trap to the waste outlet.

3. Mix the mortar and use a trowel to lay a thin bed on the floor where the tray will be positioned. Rest the tray in place.

4. Bed the tray down into the mortar and level it with a spirit level. If you can’t get it exactly level you may need to take up the tray and adjust the mortar. Tidy the edges and remove any excess mortar with the trowel. Open the floor hatch and connect the trap to the waste pipe.

Fitting the shower enclosure

The shower tray, mixer valve and all pipework and tiling should already be in place before you fit the shower enclosure. Shown here is a corner enclosure with curved sliding doors; there are lots of designs available, each installed in a slightly different way, so do read the manufacturer’s installation instructions. With any enclosure it is vital that the wall and tray are fully waterproof, and that the uprights of the frame are vertical.

1. Lie the two fixed side panels flat and run a generous bead of sanitary silicone sealant into the curved channels at the top and bottom. Then attach the head and sill rails with the screws provided; don’t overtighten them.

2. Slide the plastic guide tracks into the head and sill rails.

3. Use a junior hacksaw to shorten the plastic guide tracks if they are too long.

4. Push two door stops into the guide track in the head and sill rails. Move them into the middle but don’t fix them yet.

5. Stand the shower enclosure upright and slide the curved sliding doors into the head and sill rails, making quite sure that the doors are the right way around. Then insert another doorstop into both the head and sill rails.

6. Attach the wall channels to each side of the enclosure and stand it on the tray. Check it is vertical using a spirit level. From the inside of the enclosure, use a chinagraph pencil to mark the position for the fixing holes through the pre-drilled holes in the wall channels.

7. Remove the enclosure and check for hidden pipes and cables behind the fixing positions with an electronic detector. If all is clear then drill fixing holes in the marked positions. Push wallplugs into the holes, making sure they go in beyond the depth of the tile.

8. Run a continuous bead of sanitary silicone sealant down both wall channels. Put the enclosure onto the base, and screw in the fixing screws. Remove any excess sealant. Refer to the instructions to make final adjustments to the sliding doors.

9. From the inside, drill through the holes in the wall channels and into the frame. Secure with the screws provided and cover the heads with screw caps. Drill through the plastic track and inner head channel then screw the doorstops in position.

10. Seal the join between the tray and the tiled wall with a continuous bead of sanitary silicone sealant. Do the same around the outside edges of the enclosure.