Shared septic tanks

Many rural properties have off mains drainage systems in place, typically because they are too far away from a main sewer to be able to connect to it.

There are three main types of off mains drainage tanks - septic tanks, sewage treatment plants and cesspits.

The most common type of off mains drainage tank is a septic tank, so throughout this guide we will refer to `septic tanks’ but this could also relate to any type of shared drainage tank.

Septic tanks can serve individual properties or multiple properties. In the instance of a septic tank shared by two or more properties, the tank will typically be situated within the boundary of one of the properties that connects to it. Occasionally, a shared septic tank (or any soakaway system into which it connects) might be located within third party land which is not owned by anyone who connects into the tank. It is important to identify exactly where any shared septic tank lies, and to know who owns the land on which it is situated.

If you are buying a property with a shared septic tank, it is also important to know whether there have been any historic issues with other property owners or third party land owners, particularly around the sharing of costs or any access problems.

Septic tanks require routine emptying, typically annually, and may also require repair or replacement if they become damaged. In these instances, the costs should be shared equally amongst the properties connected to the tank. If, for example, a shared septic tank caused a pollution, and it was necessary for the Environmental Health Team from the Local Authority to intervene in order to resolve the solution, they would split any costs incurred equally across all properties connected. Similarly, in the instance of a damaged shared septic tank in which the damage is covered by the buildings insurance of each property, insurers would also split the costs of any works equally across each property.

The only exception to this is if something different is specified in the deeds of the properties involved - this is rare, but we have seen a case in which the deeds state an unequal share of costs.

Often, arrangements for the ongoing management of a shared septic tank, including the details of any rights of access, are covered in the deeds of each property, or can be detailed in a separate formal arrangement. However, occasionally these arrangements can be more informal, and based on a verbal agreement between the property owners involved.

It is easiest for all parties if a formal agreement is set in place, particularly if the deeds do not make reference to the drainage system. Some property owners choose to set up a separate residents’ association into which each property pays in an agreed amount each year, in order to cover any routine emptying costs. It can remove the need for any awkward conversations and can set down exactly how any problems might be dealt with.

If you are buying a property which has a shared septic tank, it is crucial to get an understanding as to what is currently in place. A lack of any formal agreement can cause real headaches for everyone involved, and our advice would always be to ensure that some form of formal written agreement is in place.

If your property connects to a shared septic tank, it is possible that the tank itself is situated outside of the boundary of your property. However, you will remain partly responsible for ensuring that the tank is regularly emptied (and, in the case of a sewage treatment plant, regularly serviced) and for repairing any damage which might occur.

Similarly, if the drainage system is ever found to be causing a pollution, you will be legally responsible for resolving the matter. The deeds of the property should specify that you have rights of access to the septic tank for the purposes of emptying and repair. The general rule of thumb is that if you need to access a tank into which your property connects, but which is not within the boundary of your property, you should provide at least a week’s notice of your intention to access the tank to the owner of the property on whose land it is situated.