Sharing a septic tank with your neighbours: who is responsible?
Two or three houses on one septic tank is common off the mains. Here is who the rules hold responsible, who pays for emptying, and what to agree in writing.
Read the guideReplacing a septic tank is usually permitted development, but building regulations still apply and some sites need consent. Here is what applies when.
For most domestic replacements you will not need planning permission, but you will need to satisfy building regulations. Planning becomes relevant on listed buildings, in conservation areas, in National Parks, where the system serves a new dwelling or a change of use, and where anything sits above ground.
People use “permission” loosely, and it causes genuine confusion on drainage projects because three separate regimes apply and they have nothing to do with each other.
Planning permission is about land use and what a development looks like. Building regulations are about how the thing is built and whether it works — Part H covers drainage and waste disposal, and it applies to off-mains systems. The General Binding Rules, enforced by the Environment Agency, govern the discharge itself. You can satisfy one and fall foul of another.
For a typical replacement — an old septic tank swapped for a treatment plant on the same property — the usual position is: no planning application needed, building regulations yes, binding rules yes.
Installing or replacing a sewage treatment plant or septic tank for an existing house normally falls within permitted development. The unit is buried, it serves the existing dwelling, and there is no change of use. That covers the majority of the work we do.
The reasoning is straightforward: planning is concerned with visual and land-use impact, and a tank in a hole with a lid at ground level has very little of either.
This is the part people skip. A new or replacement off-mains system is notifiable work under Part H. In practice that means the installation has to meet the standard for siting, construction and discharge, and it has to be signed off.
It matters later rather than sooner. Building control sign-off is one of the documents a buyer’s solicitor will ask for, and its absence is the kind of thing that stalls a sale years after the work was done. We have been called to properties where a perfectly good plant was installed competently and nobody notified anybody, and the seller is the one paying to establish compliance retrospectively.
Keep the building control paperwork, the percolation test results, the field design, the installation invoice and the manufacturer’s manual together with the house papers. Those five documents answer nearly every drainage question a conveyancer will ask. We have written separately about what comes up when you sell.
Independent of planning, there are practical limits on where a system can go: minimum distances from buildings, boundaries, watercourses, springs, wells, boreholes and anywhere used for water supply, plus access for a tanker to reach it for emptying. On a tight plot those constraints often decide the design before any regulator has an opinion.
Access is the one that gets forgotten. A tank sited where no tanker can reach it has to be emptied with long hose runs for the rest of its life, at a cost on every visit.
For a straightforward replacement on an existing house: we survey the site and establish where the current system discharges, carry out trial holes and a percolation test if a drainage field is involved, design and size the system, confirm whether planning is needed for your specific property, handle the building control notification, install it and hand over the paperwork.
If you are in a National Park, a conservation area or a listed building, we will tell you that at the survey rather than halfway through. A five-minute call to the planning department before anything is ordered has saved several of our customers a great deal of trouble.
For a straight answer on your own property, call 07884 111 641 or read more about how we handle installations.
People usually ask about planning first because it is the word they know, and it is the least likely of the three regimes to apply. The order that saves time is: where does the discharge go and is it lawful; what does the ground allow; and only then, does anything about this installation need consent.
Answering them that way round means you discover any genuine obstacle before you have chosen a system, rather than after you have ordered one.
The planning authority will confirm whether your property has restricted permitted development rights, whether it sits in a conservation area or National Park, and whether an Article 4 direction applies. That is a phone call or a short email and it costs nothing. Listed building status is a matter of public record and equally quick to check.
Neither of those conversations commits you to anything, and both are considerably cheaper than a retrospective application on a tank that is already in the ground.
Normally not planning permission, but the work is still notifiable under building regulations and the discharge still has to meet the binding rules.
Permitted development rights are often restricted in National Parks, so check with the authority before ordering anything. It is a short call and it settles the question.
It can often be resolved with a survey, a condition report and a regularisation route through building control. Deal with it before you market the house, not during the sale.
Generally not planning permission on an existing property, but it must be correctly sized from a percolation test and sited at the required distances, and it falls under building regulations.
Septic tank emptying, installations, servicing and drainage across Derbyshire, Sheffield and Yorkshire — 24/7.
Two or three houses on one septic tank is common off the mains. Here is who the rules hold responsible, who pays for emptying, and what to agree in writing.
Read the guideOff-mains drainage now comes up in every sale. The questions the buyer’s solicitor asks, and the paperwork to have ready before you list.
Read the guideIf your septic tank discharges to a ditch or stream it must be replaced or redirected. What the General Binding Rules require and when they bite.
Read the guide