Drainage and septic tanks

Can grease in a kitchen drain be written up as a collapsed sewer?

It should not be. Grease, fat and food block a small-bore kitchen run and a gulley. That is a blockage. A collapsed pipe is a structural failure of the drain. A surveyor who sees a slow gulley or a smell can say so. They cannot see a collapse without a camera. Do not price a new sewer for a greasy trap.

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?

Kitchen wastes are the usual source. The trap under the sink and the gulley outside are the first places a blockage shows. Approved Document H expects foul drainage to carry sewage, not to be a specification for your house’s trap. Clearing grease is maintenance. A camera is the step if the surveyor thinks the underground pipe is at fault, for example because several fittings back up together.

RICS surveys do not jet drains as standard. If the report says “gulley slow”, ask whether any chamber was backing up. If not, start with a clean, not a relay. There is no national price. A drainage firm will quote once they know whether they are cleaning or excavating.

What should you ask your surveyor?

Which fitting was slow, and did any chamber surcharge?
Did you see fat in the gulley, or only a slow empty?
Are you recommending clearing, a camera, or both?

What are the typical next steps?

Do not pour chemicals through a blocked gulley on the day of the survey.
If only the kitchen is slow, say that when you ask for a price.
If toilets and the kitchen all back up, stop using them and get a drainage firm. That pattern is no longer “just grease”.

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 grease trap required in a house?

Ordinary houses usually have a trap under the sink, not a commercial grease interceptor. The survey should not import a restaurant standard.

Does a slow drain mean the septic tank is full?

Only if the house is on a tank and the backup is at that system. A urban kitchen gulley is a different pipe. Read which system the report names.