How to connect Shower tray drain to Wet room Floor waste?

You can connect the waste without digging up the floor using one of these proven methods:
Option 1 — Raised tray with above-floor trap (cleanest solution)
Fit a low-profile or telescopic waste trap that sits entirely above the existing floor surface. These can be as compact as 50mm in height
Raise the shower tray slightly using a purpose-made riser kit or slim battens and decking board — this creates just enough space under the tray for the trap and pipework
Run the waste pipe across the surface of the floor in a shallow channel or boxing — it can be hidden behind a low tiled plinth or enclosure panel
The pipe must have a fall of roughly 25mm per metre toward the drain — this is essential for proper drainage
Connect into the existing floor drain using a flexible rubber connector (such as a Fernco coupler) or a compression fitting — these slip over different pipe sizes and make a watertight seal without needing exact measurements
Option 2 — Offset connection
If the existing floor drain is close but not directly under the tray, use a short length of flexible waste pipe to bridge the gap
Flexible waste connectors are widely available and can be routed gently across the surface
Keep bends as gentle as possible — sharp angles will block easily
Option 3 — Access through the ceiling below
If the room beneath is accessible, cut a small neat patch in the ceiling directly below the waste position
This gives you enough room to make the connection from below without disturbing the wet floor
The ceiling patch can be made good afterwards with plaster and paint — far less work than lifting the floor
Important points:
Check the depth of your chosen waste trap before buying — compact "easy-clean" or "slimline" models are designed specifically for tight spaces
Ensure the waste pipe maintains a steady downward slope — any flat or upward sections will cause water to pool and smell
If you raise the tray, remember to adjust the door threshold or add a small step so it is safe to use
Summary:
The raised tray with slim trap and surface-run pipe is the most straightforward method and will not damage your new floor. It will add roughly 60mm to the finished height of the tray, but it is fully reversible and leaves the existing floor intact.

It may be possible to connect the shower tray waste to the existing wet room drain without breaking into the floor, but it depends on the type of drain fitted and whether you have enough height to accommodate the new waste pipe.

The existing floor drain will already have a trap, so you need to ensure the new connection doesn't create a double-trap arrangement, which can cause slow drainage and blockages.

The best option would be to remove the existing drain cover and inspect the waste outlet to see whether a suitable adaptor or direct connection can be made. If this isn't possible, you may need to raise the shower tray on a suitable riser kit to allow the waste pipe to run above the existing floor.

I wouldn't recommend simply running the shower tray waste into the existing floor drain or sealing a pipe into the drain opening, as this could lead to leaks, unpleasant smells and future maintenance issues.

If a suitable connection cannot be achieved from above, some alterations to the existing drainage may be unavoidable to ensure a properly sealed, accessible and reliable installation.

In most cases you won’t be able to connect a shower tray directly into an existing wet room floor waste without opening the floor.
Wet room drains are designed to take water directly at floor level with the correct falls built into the floor. A shower tray waste needs its own trap and pipework with the correct fall to the drainage system.
Trying to connect into the floor drain from above usually isn’t practical and can lead to issues with flow, smells (trap problems), or leaks.
Proper options would be: • Lift the floor locally and connect the tray waste into the existing pipework below
• Or run a new waste pipe from the tray to a suitable connection point
If you’re trying to avoid breaking the floor, sometimes a raised tray with accessible pipework can work, but it depends on layout.
Realistically, for a proper long-term job, some level of floor access is usually required.

Usually, not neatly and not reliably.

A shower tray waste normally needs its own trap/waste connection directly below the tray, and wet-room drains are built around the floor, forming a gradient for drainage and waterproofing of the wet-room system. In other words, a tray waste is not normally designed to just “plug into” an existing floor drain from above without access to the drainage below.

So in practice, you have 3 realistic options:

1. Best option: open the floor locally and connect properly
That is the standard way. Wet-room and tray installation guidance assumes access is needed to align the waste outlet and drain connection correctly.

2. Use a raised shower tray on a riser/waste kit
If you do not want to break the finished floor, a raised tray can create enough space beneath it for the tray trap and waste run. Bathroom guidance notes that trays sometimes need to be lifted off the floor so the waste can run away properly to the nearest drain point.

3. Use a pumped waste system
If the floor is effectively "unbreachable,” a pumped drain/shower waste pump is a recognised solution specifically for floors where normal gravity drainage cannot be achieved.

What I would not recommend is trying to:

push the tray waste straight into the floor drain opening from above,
rely on a flexible hose hidden in the floor,
or seal one waste fitting onto another without proper access.
That usually leads to poor flow, trap problems, smells, or leaks. This is an inference from how tray wastes and wet-room drains are designed as separate systems requiring proper drainage alignment and waterproofing

Ideally you need to dig out the floor so that the new shower waste connects directly into the original waste pipe

To connect your shower tray waste to an existing wet room drain without breaking the floor, you'll need to lift some flooring to access the existing gully/pipe, use flexible connectors or solvent/compression fittings to join the new tray waste to the existing pipework, ensuring the trap is correctly positioned and sealed, then refill and screed around the tray to create a flush, watertight finish, potentially using tile backer boards for height.