Advice
Selling a house with a septic tank
What conveyancing now asks about off-mains drainage, why compliance surfaces mid-sale, and how to keep a tank from holding up your move.
Drainage is one of the quiet ways a rural house sale gets held up. The system worked fine for years, nobody thought about it, and then the buyer’s solicitor asks a question the seller cannot answer, and a sale that was progressing stalls while it gets sorted out under time pressure.
It does not have to go that way. The questions are predictable, and a system dealt with before the property is marketed is a system that does not become a negotiation later.
What conveyancing now asks
Off-mains drainage has become a standard part of the conveyancing enquiries on any rural property. Solicitors and surveyors routinely ask what the system is, whether it complies with the General Binding Rules, when it was last emptied or serviced, and whether the paperwork exists to show it. A seller who can answer those with documents is in a strong position; one who cannot invites the buyer to assume the worst and price accordingly.
- What type of system serves the property: septic tank, sewage treatment plant or cesspit.
- Whether it complies with the 2020 General Binding Rules, in particular that a septic tank does not discharge to a watercourse.
- A history of emptying and, for a treatment plant, servicing, with records where possible.
- Where the tank and drainage field are, and who owns and maintains any shared drainage.
The rule that catches sellers out
The change most likely to cause a problem arrived in 2020: a septic tank may no longer discharge to a ditch, stream, brook or river. Plenty of older Shropshire systems were built exactly that way, because piping the tank outfall to the nearest ditch was normal practice for decades in a county laced with watercourses. If a tank still discharges like that, it is non-compliant today, and a sale is exactly when that comes to light.
The fix is usually a drainage field where the ground allows one, or a treatment plant where it does not. Which applies depends on the ground, and on the clays common across north Shropshire a treatment plant is frequently the practical route. None of it is a dead end, but all of it takes time, which is the argument for starting before the property is on the market.
The seller’s stronger position
A seller who gets the system inspected before listing controls the timing. If it complies, the inspection is evidence that heads off the buyer’s doubts. If it does not, the work can be planned and priced calmly, and either done before marketing or disclosed with a clear quote rather than discovered mid-sale and negotiated in a rush. The difference between the two situations is often thousands of pounds of negotiating position, and weeks on the timeline.
The buyer’s side of the same coin
If you are buying a rural property, the equivalent move is a pre-purchase drainage survey, ideally with a camera survey of the drains and an inspection of the tank and its records. Drainage faults are invisible at a viewing and can cost thousands, and a survey before exchange means any upgrade cost is priced into the deal rather than discovered after completion, when it is entirely yours.
Last reviewed 23 July 2026.
Frequently asked questions
Do I legally have to fix my septic tank before selling?
If the tank discharges to a watercourse, it is non-compliant with the General Binding Rules and the responsibility to correct it does not disappear at sale. In practice, compliance is dealt with as part of the transaction: either the seller resolves it beforehand, or it becomes a negotiated point, usually with the buyer wanting a price reduction or the work done before completion.
Can a non-compliant septic tank stop a sale going through?
It can certainly delay one and reduce the price. A buyer’s solicitor flagging a non-compliant system mid-sale creates a negotiation with the clock running, and buyers reliably assume a higher cost than the actual fix. Sorting it before marketing removes the problem rather than handing it to the other side.
What paperwork should I have ready as a seller?
Records of emptying and, for a treatment plant, servicing; any installation or building-regulations documents; and, if the system has been assessed against the General Binding Rules, that assessment. The more of the system’s history you can evidence, the less room there is for a buyer to assume the worst.
Not sure what your system needs?
Describe the problem and we will tell you what you are most likely dealing with, and put you in touch with a local specialist where one covers your area. No charge for that, and no obligation.