Why does water sit in my shower tray instead of draining?

A shower tray drains by gravity down a moulded fall of a few millimetres. That fall only works if the tray sits dead flat on its support, and a surprising number are fitted on feet or on incomplete mortar beds that let the middle sag.

What you'll need

• A jug of water
• A spirit level, ideally a short one
• A drain snake or a wire hook

Step by step

1. Do the jug test.Pour two litres in at the far end from the waste. Slow but complete drainage means a restriction. Fast drainage with a residual puddle means the tray shape is the problem.
2. Clear the waste first regardless.Lift the grate, hook out the hair, and take the trap apart if it is accessible. Even a tray with a fall drains slowly through a half-blocked waste.
3. Check the flow rate of the waste.A shower waste should swallow water as fast as the shower delivers it. If the tray fills while you shower and empties afterwards, the waste is undersized or restricted, not the tray.
4. Put a level across the tray in several directions.Lay a short level from the waste towards each edge. You should see a consistent slight fall towards the outlet everywhere.
5. Press on the tray and watch the puddle.If standing on the tray moves the puddle or makes the water drain, the tray is flexing on an incomplete bed. That is a fitting fault, not a maintenance one.
6. Check for a shallow spot at the edge.Water sitting in a thin film right at one edge is usually a tray that has dropped where a leg or the mortar bed has failed at that corner.
7. Decide honestly whether it matters.A film of water that dries in an hour is cosmetic. A standing puddle that never dries breeds mould and stains, and justifies lifting the tray.
8. Understand what relaying involves.A tray that has settled has to come out: silicone cut, waste disconnected, tray lifted, and a full mortar bed laid so it is supported everywhere. Tiles at the bottom edge will usually be damaged. It is not a quick fix.
9. Reseal properly afterwards.Any tray that has been moved needs the joint to the wall cut out and resealed, with the tray weighted or occupied during the cure.

Tips

• Time how long the puddle takes to dry. Under an hour is normal for any tray; overnight is not.
• A tray fitted on adjustable legs alone, with no mortar bed, will always feel lively and often puddles.
• Check the waste before blaming the tray — it is the cheap possibility and it is the more common one.

Common mistakes

• Assuming any standing water means a blockage — A tray that drains quickly but leaves a fixed puddle has a shape problem. Rodding the waste repeatedly does nothing and can damage the trap seal.
• Trying to build up the low spot with sealant — Silicone in the tray floor does not bond durably to a wet, trafficked surface, and it traps water underneath itself. It always peels within months.

If it doesn't work

Questions people ask