Drainage and septic tanks
The tank has an inlet and the surveyor found no outlet pipe after looking around the lid. Why must that not be described as a treatment plant that discharges?
It must not be described as a treatment plant that discharges because no outlet pipe was found. A treatment plant discharges treated liquid. What was seen is a tank with an inlet and no outlet around the lid. A cesspool holds sewage and is emptied. A septic tank and a treatment plant are different. The survey only records what was seen. It has not certified the tank type, and it has not found a discharge to describe.
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?
Looking around a lid is a surface look. Pipes can be buried beyond that circle, so the survey has not proved a cesspool by a full excavation. What it has done is refuse a description the evidence does not support. Calling this a treatment plant that discharges would invent an outlet the surveyor did not find. Emptying, permits and how any real discharge is made are outside a look at a lid. The sentence in the report should stay with the inlet and the missing outlet.
Ask the solicitor for emptying records, any permit, and what the seller says the tank is, and keep those papers off the survey's wording. If the type must be known, a drainage specialist can trace an outlet properly. Do not rewrite the report as a discharging plant to make a mortgage form easier. The inspection has not seen a discharge and must not be quoted as if it had.
What should you ask your surveyor?
- What pipe did you see, and what outlet did you fail to find?
- Why must the tank not be called a treatment plant that discharges?
- Did you certify the tank type, or only record the lid and the pipes in view?
What are the typical next steps?
- Do not describe the tank as a treatment plant that discharges.
- Ask the solicitor for emptying records and any permit.
- Get a drainage specialist to trace an outlet if the type must be known.
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
If the lid smells, does that prove a cesspool?
Smell shows sewage, not the full classification. A cesspool holds sewage and is emptied, and a septic tank and a treatment plant are different, but the survey only records what was seen: an inlet and no outlet around the lid. That is why it must not be called a discharging plant. It is not a finished certificate that the tank is a cesspool.
Can a buried pipe you did not dig up be assumed?
No. An assumed outlet is how a treatment plant gets written into a report that did not find one. The surveyor looked around the lid and found no outlet pipe. Buried pipes remain possible, which is why the type was not certified, and they are not a reason to describe a discharge that was not seen.