Drainage and septic tanks
Water remained in the shower gully after a short run of the tap. Is that, by itself, failed wet-room tanking?
No. Water that remained in the shower gully after a short run of the tap is not, by itself, failed wet-room tanking. The survey saw a gully that did not clear quickly. That can be a slow outlet, a flat trap or debris. Tanking is the hidden layer under the finishes, and a visual survey cannot see it through the tray. Standing water in the gully is not a test of that layer. Ask a plumber about the outlet. Do not treat one slow gully as a failed wet room.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
A gully is the waste you can see. Tanking, where a wet room has it, sits under the floor and sometimes up the walls, covered by the finish. Water left in the gully after a short run says the outlet emptied slowly. It does not say a membrane has failed, and it does not say a membrane was installed. The survey did not flood the room or lift the tray. One slow outlet is one observation, not a verdict on a hidden layer.
Ask a plumber to clear and run the gully, and to say whether the trap, the fall or a blockage is the cause. Do not smash the finish looking for a membrane because a puddle sat in the outlet. If the seller calls the room a wet room, that claim is about what is under the tiles, and it needs its own answer. Keep the survey sentence as a slow gully, not as failed tanking.
What should you ask your surveyor?
- How long did water sit in the shower gully after you stopped the tap?
- Did you see a blocked grate, a flat trap, or only the standing water?
- Any staining beyond the gully that you are distinguishing from this slow outlet?
What are the typical next steps?
- Treat the standing water as a slow gully, not as failed tanking.
- Ask a plumber to clear the outlet and say why it held water.
- Do not lift tiles on a viewing to hunt for a membrane.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Does a slow shower gully mean the floor membrane has split?
No. The survey saw water in the gully. It did not see a membrane, and a slow outlet has ordinary causes that are not tanking.
If the gully clears after a longer run, is the wet room proved?
No. A gully that eventually empties still says nothing about any hidden tanking. The survey cannot see that layer through the finish.