Geberit Frame Installation & Connection (Duofix / Kombifix)

Both systems carry a wall-hung WC without trouble, as long as they are anchored properly. The main differences are the type of wall they belong in and how they are covered.

• Duofix is a self-supporting steel frame. It is fixed to the floor and to the wall and suits a false wall (a service wall built in front of the main wall) or a plasterboard partition. Fitting is quicker and needs no bricklaying.
• Kombifix is a frame designed to be built into a masonry wall or a masonry recess. It is fixed to solid masonry and then bricked in or built into the structure.

The option frame installation plus masonry boxing includes the frame and a short wall built around it, usually from aerated concrete blocks or bricks. Aerated concrete is easier to cut, so the work goes faster. Brick takes more effort to shape but is harder. The boxing can go right up to the ceiling, or stop at frame height and leave a handy shelf on top. Plan its thickness in advance, because it takes up floor space in the room.

Frames also differ in height. Standard frames are roughly 112 cm tall. For loft rooms or under a window there are lower versions of around 80 cm. Before you buy, check that the pan and flush plate you have chosen fit the frame, and read the manufacturer's installation instructions.

An experienced plumber usually works in roughly this order:

1. Measures the WC position: distance from the side walls, the position of the waste pipe and the height of the finished floor, including tiles.
2. Sets the frame in place, levels it and adjusts the extending feet so that the top edge of the pan usually ends up about 40 to 45 cm above the finished floor. For an accessible bathroom, the height is agreed individually.
3. Anchors the frame to the floor and to a solid wall. In masonry this means suitable wall plugs or chemical anchors; in a plasterboard wall the frame is fixed to the supporting studs.
4. Connects the waste. The waste pipe needs a steady fall in line with EN standards and the manufacturer's instructions. If the outlet does not line up exactly, an offset connector helps.
5. Flushes out the water supply pipe and connects the cistern through an isolating valve.
6. Carries out a pressure test and a flush test. Only when nothing drips and the water drains away freely is the frame covered.
7. Boxes the frame in with masonry or covers it with moisture-resistant plasterboard. For wall-hung WCs, manufacturers usually recommend two layers of board. Cuts openings for the flush plate and the pan connections.
8. Prepares the surface for tiling: primer on masonry, or jointing tape and filler on plasterboard joints.

After tiling, the pan is mounted on an isolation pad, which reduces noise and protects the tiles, and the flush plate goes on. The nuts are tightened evenly so the ceramic does not crack.

How much work is involved, and therefore the final cost, depends on what the tradesperson finds on site.

• It is easier in a new build or a full renovation, when the water and waste are already in exactly the right place for the frame and the floor is level.
• It is harder when replacing a floor-standing toilet in an older flat. The waste outlet is often too low or in a different place, the pipework is old, and sometimes walls or floors need chasing.
• Moving the waste pipe or running new water pipes adds extra plumbing work.
• Masonry boxing takes more work than plasterboard, and full-height boxing takes more than half-height.
• An uneven floor or a weak wall means extra levelling and anchoring.

In a block of flats, any work on the shared soil stack must be agreed in advance with the building management or owners' association. If you are changing the layout or touching load-bearing parts of the building, check with your local building authority what the local building regulations require. Do not assume that a simple notification is always enough.

Once the work is finished, the frame is hidden in the wall. Any mistake means breaking out the tiles. In practice the same ones come up again and again:

• Weak anchoring. Over time the pan moves and a joint or tile cracks.
• Wrong height. If nobody allows for the thickness of the floor tiles, the pan ends up too low or too high.
• Not enough fall on the waste. Water drains slowly and the drain smells.
• Skipped leak test. A small leak only shows itself later as a damp wall.
• One thin layer of plasterboard. The area under the pan can flex.
• Non-original seals and fixing kits. They lose their elasticity over time and start to leak.

If you have some building experience and the water supply and waste are already in exactly the right place for the frame, you can fit it yourself. If the waste needs moving or the pipework needs changing, call a plumber. Always follow the instructions for your specific frame.

1. Turn off the main water supply and check that nothing runs from the outlet.
2. Mark the centre line of the WC and the finished floor height, including tiles.
3. Stand the frame in place, set the feet to the required height and lock them.
4. Level the frame in every direction with a spirit level.
5. Drill the holes and anchor the frame to the floor and wall with fixings suited to the surface.
6. Push the frame from different sides and make sure it does not move.
7. Connect the waste bend to the drain and check the fall.
8. Flush out the supply pipe and connect the cistern through the isolating valve.
9. Turn the water on, let the cistern fill and flush several times through the test opening.
10. Leave the water under pressure for at least a few hours and check every joint with a dry paper towel.
11. Only then cover or box in the frame.

• The frame is solid and does not rock when you push it
• The pan height matches what was agreed and the pan is level
• A pressure test and a flush test were done before the frame was covered
• All joints on the supply and waste are dry
• The cistern fills smoothly and the valve closes fully once it is full
• Both full and half flush work and the water drains away without slowing
• The opening behind the flush plate is accessible for servicing
• The boxing is straight, free of cracks and ready for tiling
• The pan sits on an isolation pad and the joint with the tiles is sealed with sanitary silicone
• You have received the instructions and the frame model details for future spare parts