Septic tank rules when selling a house — the 2020 general binding rules

If your property is not on mains drainage, this is likely to be the slowest problem in your sale, and the most expensive one to discover late.

The rule that catches people

Under the general binding rules for small sewage discharges in England, a septic tank discharging to a watercourse — a stream, ditch, river or any surface water — needed to be replaced or upgraded. The deadline was 1 January 2020, or when the property is sold, whichever comes first.

That second clause is the one that matters to you. A sale is a trigger.

The compliant arrangements are broadly either discharging to ground through a properly constructed drainage field, or replacing the septic tank with a package treatment plant that meets the relevant standard.

What buyers ask for

• What the system is — septic tank, treatment plant, or cesspool
• Where it discharges
• When it was last emptied, and by whom
• Servicing records, particularly for a treatment plant
• Whether it serves only your property or is shared
• Any permit, if one is required

Why this one is different. Most paperwork problems in a sale are administrative. This one can be a genuine capital cost running to several thousand pounds, and the work takes weeks once specified. Finding out at survey stage hands the buyer a very large lever at the exact moment you are least able to resist it.

What to do before you list

1. Establish what you have and where it goes. Previous owners’ paperwork, an existing drainage plan, or a drainage survey.
2. Find your emptying records. Most tanks are emptied annually; the contractor will have a record even if you do not.
3. If it discharges to surface water, get advice now. Not from a website — from a drainage engineer and your conveyancer, because the options and the costs vary enormously with the site.
4. If it is shared with a neighbour, find the agreement, or establish that there isn’t one. Shared systems generate their own set of enquiries about responsibility and cost-sharing.

If you are on mains drainage

Then this takes five minutes to confirm and you can forget it entirely. Which is itself worth doing — being able to answer “mains drainage, connected, here is the confirmation” closes an enquiry before it opens.

A note on Wales and on scope

The general binding rules described here apply in England. Wales has its own regulatory arrangements for small sewage discharges. If your property is in Wales, treat the principle as the same — buyers will ask what you have and how it is maintained — but check the specific requirements with your conveyancer.