Drainage and septic tanks
The report mentions a washing-machine standpipe next to the under-sink waste. Has a connection into the wrong stack been tested, or only named?
A connection into the wrong stack has been named, not tested. The report places a washing-machine standpipe next to the under-sink waste and describes a connection that appears to enter the wrong stack. Nobody dyed the pipe, ran a camera, or proved where the water goes. The standpipe and the nearby waste were seen. The route called wrong was not demonstrated. The survey has not decided the machine will discharge into the wrong drain, and it has not cleared the connection either.
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 washing-machine standpipe should drop into a trapped waste that joins a proper foul stack, not into a rainwater pipe or a stack that does not serve the foul drainage. Pipes under a sink are crowded. The surveyor sees the standpipe, the sink waste and a joint that looks misplaced. They do not see the hidden length unless it is opened, and this visit did not test it with water or dye. A suspicious joint is a reason to check. It is not yet a proved misconnection.
Ask a plumber or a drainage firm to trace the standpipe with water or dye before anyone reroutes it. The survey has not done that trace and has not specified new pipework. Tell the solicitor the wrong stack was named from what could be seen, not confirmed. Do not describe the house as draining foul water to the surface on the strength of this note. If a misconnection is confirmed later, that is new information. Until then keep the standpipe, the sink waste and the untested route separate.
What should you ask your surveyor?
- Which stack did the standpipe appear to join, and how was that stack recognised?
- Was the joint visible, or was the route inferred under the sink?
- Did you run the washing machine or pour water, or was the note visual only?
What are the typical next steps?
- Treat the wrong-stack connection as named and not traced.
- Ask a plumber to prove the route with water or dye.
- Tell the solicitor the misconnection is not yet confirmed.
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
Is a standpipe beside the sink waste always wrong?
No. A standpipe next to the under-sink waste is a normal place for a machine, provided it joins the foul waste properly. The survey named a connection into the wrong stack and did not test it. Neighbourhood of the sink is not the defect. The untested route is. Do not move the machine just because it stands there.
Could the machine still be connected correctly behind the cabinet?
Yes. Under-sink pipes are easy to misread, and the survey did not trace them with dye or a camera. A joint that looks wrong may join the foul stack just out of sight. It may also be the misconnection the note suspects. Neither has been proved. A plumber needs to follow the water.