Around a million homes in the UK aren’t connected to mains drainage, and most of them rely on a septic tank or a small treatment plant somewhere in the garden. If yours is one of them, the tank will come up during the sale, and how it comes up depends on whether you’ve got ahead of it. Buyers from towns often don’t know what a septic tank is. Their solicitors know exactly what to ask about it. And the rules that came in a few years ago mean some tanks have to be upgraded or replaced before a sale can complete. We’ll take you through the rules, the likely costs, what buyers will want to see, and how to keep the tank from slowing your sale down.
The Rules You Need To Know
The General Binding Rules
In England, small sewage discharges are governed by the General Binding Rules. The most important one for sellers concerns where your tank discharges to. A septic tank that discharges directly into a ditch, stream, river or any other surface water is no longer permitted. If yours does, it must be replaced with a sewage treatment plant, or the discharge must be redirected to a properly designed drainage field, and when a property is sold the rules require this to be sorted out before completion. The buyer and seller can agree who does the work, but it has to be done.
A septic tank that discharges to a drainage field in the ground is fine, as long as the tank and field are properly maintained, the discharge volume is under the permitted daily limit, and the field isn’t within a groundwater protection zone.
Wales
Wales runs its own scheme, and all septic tanks and treatment plants there need to be registered with Natural Resources Wales. If you’re selling in Wales, check the registration is in place, because a buyer’s solicitor will ask for it.
Disclosure
The property information form asks whether the property is connected to mains drainage and, if not, what system is in place, where it discharges, when it was last emptied and whether it’s shared with any other property. Answer fully, because the buyer’s drainage search will confirm the absence of mains drainage regardless.
What A Septic Tank Costs A Seller
The figures vary a lot with location, ground conditions and the size of the system, but as a guide:
- Emptying a tank costs somewhere between £150 and £350, and most tanks need it once a year
- A specialist septic tank survey, which some buyers commission, runs to a few hundred pounds
- Installing a new drainage field to replace a surface water discharge typically costs from around £3,000 to £8,000 depending on the ground and the size required
- Replacing a septic tank with a treatment plant commonly costs between £5,000 and £12,000 installed, and more where access is difficult or the ground is unsuitable
- Connecting to mains sewerage where it’s available nearby can be anywhere from a few thousand pounds to far more if the connection is long or crosses other land
If your tank is compliant, your costs are limited to emptying it and handing over the paperwork. If it isn’t, the replacement cost is either a sum you spend before selling or a sum the buyer will deduct from the price.
What Buyers Worry About
Most buyer concerns come down to a handful of questions, and having the answers ready removes them.
- Is it compliant? They’ll want to know where it discharges and whether it meets the rules.
- Where is it? Buyers want to know the tank’s location relative to the house, the boundary and any watercourse, and whether the drainage field runs under anything they might want to build on.
- Is it shared? Tanks serving more than one property come with shared responsibilities and sometimes informal arrangements that buyers’ solicitors dislike.
- When was it last emptied and serviced? A tank that hasn’t been emptied for years suggests neglect.
- Does the ground drain properly? Signs of pooling, smells or lush grass over the drainage field point to a failing system.
- Who maintains it and what does it cost? Buyers from mains-drained homes want a sense of the ongoing commitment.
Mortgage lenders generally accept septic tanks, but their surveyors will note any signs of failure and may recommend a specialist inspection, and some lenders will retain funds if the system needs replacing.
Preparing The Tank For Sale
A few steps taken early make a real difference. Have the tank emptied and keep the receipt. Locate the tank, the manhole covers and the drainage field, and be ready to point them out. Dig out any installation records, planning permissions, building regulations approvals or previous surveys. If you’re unsure whether the tank complies, get a drainage engineer to inspect it and tell you in writing. If it discharges to surface water, decide whether you’ll replace it before selling or negotiate the cost with the buyer. And if the tank is shared, put the arrangement in writing with your neighbour if it isn’t already.
Selling Without Doing The Work
If the tank needs replacing and you’d prefer not to fund it, you have two routes. On the open market, you disclose the position and adjust the price, and the buyer takes on the replacement after completion. That works, but it puts off a proportion of buyers and complicates the lender’s view.
The other route is a cash sale. If you’d like to sell a rural house with a septic tank quickly, we’ll buy it whatever the state of the drainage. We’ll make an offer within 24 hours, and if the tank isn’t compliant we’ll account for the replacement in that figure and take responsibility for it after completion. We cover the survey, the legal fees and the EPC, our offers sit between 70% and 85% of market value, and we buy throughout England and Wales. The compliance requirement on sale is handled between our solicitors and yours, so it won’t stall the transaction.
FAQs
Do I have to replace my septic tank before selling?
Only if it discharges to surface water such as a ditch or stream. In that case the rules require the discharge to be dealt with before completion, and buyer and seller can agree who pays. Tanks discharging to a compliant drainage field don’t need replacing.
Can you get a mortgage on a house with a septic tank?
Yes, in most cases. Lenders accept septic tanks and treatment plants, though their surveyors may recommend a specialist inspection and the lender may retain funds if the system is failing.
How much does it cost to replace a septic tank?
A new treatment plant typically costs between £5,000 and £12,000 installed. A new drainage field alone is usually less. Difficult access or poor ground can push costs higher.
Do I need to tell the buyer the tank is shared?
Yes. The property information form asks directly, and a shared tank affects who’s responsible for emptying and repairs. Buyers’ solicitors will want the arrangement in writing.
Does a septic tank reduce the value of a house?
A compliant, well-maintained system has little effect in rural areas where buyers expect it. A non-compliant or failing system reduces value by roughly the cost of putting it right.
Will a cash buyer purchase a house with a non-compliant septic tank?
Yes. Property Buyers Today buys properties with septic tanks in any condition, and the replacement cost is reflected in the offer and handled after completion.