Is your private sewage system compliant with the relevant standards?

Wednesday, 13 September, 2023 | Gerry Rowe

During a recent pre-house-purchase tank inspection, we discovered that the septic tank on the property was not meeting the requirements because it only had a single chamber and lacked the required separation to be considered a proper septic tank. Unfortunately, it was impossible to modify the tank by adding a partition to create a second chamber due to space limitations. As a result, we advised our customer that a new system would need to be installed.

The property sellers were dissatisfied with our report and sought a second opinion from another company. They were informed that the tank was fine and met the standards because the dip pipes on the outlet had been replaced. However, they were advised that a new drainage field would be necessary, estimated to cost £6,000. Our customer approached us again to verify this information. We were uncomfortable addressing the non-compliant sewage system without resolving the underlying issues.

A simple diagram of a septic tank created by ASL Limited drainage specialists.

Consult with the authorities.

To seek clarity on the matter, we consulted the Environment Agency (EA) to validate our report. The EA confirmed that our report was primarily accurate, although the situation becomes uncertain for tanks installed before 1983. The age of the tank would need to be established to determine compliance.

The design requirements for septic tanks are outlined in section 9 of BS6297:1983. Specifically, section 9.2 mentions the need for two chambers in rectangular tanks, either as two separate or a single tank divided by a partition. Compliance with section 9.3, covering inlets and outlets, is an additional requirement and not an alternative to section 9.2.

In the current setup, there is only one tank that would need to be divided to meet the relevant British Standards. However, the existing tank lacks sufficient access to create the partition safely, and ongoing maintenance would be challenging due to the limited access to the second chamber. Simply adding a dip pipe does not make the tank compliant.

A simple diagram of a private treatment plant created by ASL Limited drainage specialists.

Standards

In cases where tanks were installed before 1983, the standards under which they were built may not be readily available. In such situations, the EA considers a single tank system without a separating wall to comply with the general binding rules for applicable standards, as long as it functions adequately and has not caused pollution.

Nevertheless, even if the tank is deemed compliant, it is advisable for the purchaser to assess the system and assume responsibility for maintaining it in line with the general binding rules and addressing any future problems.

While seeking second opinions is valuable, it is essential to consult the authoritative source, such as the EA, for accurate information. We do not aim to criticise other companies' advice, but we are committed to guiding our customers in protecting themselves against future issues.

Better to be safe than sorry

We understand the burden of unexpected costs when moving from a property. Nobody wants to pay for a new private sewage system that someone else will benefit from. Hence, we encourage property owners with private sewage systems to have them surveyed to ensure compliance and avoid unpleasant surprises, especially when planning to sell the property.

There is undoubtedly a significant ambiguity surrounding pre-1983 private sewage systems' standards. However, if a system is polluting, it must be addressed. Whether the current owner addresses it before selling the house or the new owner assumes the responsibility, it is crucial to have these discussions early in the sales process to avoid wasted time, money, and emotions.

For those unfamiliar with the different types of tanks and compliance, we have provided simple diagrams to explain the variations and which tanks would be compliant.

If you have a private sewage system and are wondering if it meets the British Standards, we strongly recommend getting it assessed. Doing so will prevent future complications. Similarly, if you are purchasing a house with a private sewage system, address any concerns before making an emotional or financial commitment.