Part of the house
The septic tank
Answered by Asked in Ayrshire · Updated · Sources at the foot
A septic tank or treatment plant cleans the sewage from a house that isn't on a public sewer, and its discharge needs SEPA authorisation.
Many rural Ayrshire homes drain to a septic tank, or to a newer package treatment plant, with the treated liquid going on to a soakaway in the ground or out to a ditch or burn. mygov.scot says you need an authorisation from SEPA for discharges from either.
The main rule to know is that SEPA moved septic tank registrations onto the Environmental Authorisations (Scotland) Regulations 2018 on 1 November 2025. Registrations held on 31 October 2025 carried over automatically, and standard conditions applied from 1 March 2026, including keeping the system and outfall fully functioning.
SEPA regulates the discharge and its guidance on maintenance asks for emptying at least once a year. New systems are designed to standards 3.8 and 3.9 of the Scottish building standards Technical Handbook. The questions below cover registration, emptying, soakaways, what to flush, treatment plants and selling up. Never open, enter or lean into a tank or chamber; look only from the ground.
The 6 questions
- Do I need to register my septic tank with SEPA?
Yes, you need to register your septic tank discharge with SEPA; registrations held on 31 October 2025 carried over automatically to the new rules, and an unregistered tank needs an application now.
- How often should a septic tank be emptied?
A septic tank should be emptied, or de-sludged, at least once a year according to SEPA, and more often if the tank is small for the household or the maker says so.
- How do we tell if the soakaway is failing?
A soakaway is usually failing when the ground over it stays wet or pools with sewage, there is a smell outside, the grass there is unusually lush, or the drains in the house slow and gurgle.
- What can go down the drain when you have a septic tank?
With a septic tank, only toilet waste, toilet paper and household washing water should go down the drain; fats, oils, chemicals, wipes and rainwater all cause trouble.
- Septic tank or treatment plant: what is the difference?
A septic tank and a treatment plant differ mainly in how well they clean sewage: a septic tank settles solids for basic treatment, while a treatment plant uses biological treatment to a much higher standard.
- What happens to the septic tank when we sell the house?
When you sell a house with a septic tank, the SEPA registration should be transferred to the buyer, so find the registration, emptying receipts and any shared-tank arrangements before the house goes on the market.