Septic tank, treatment plant or cesspit?

What is a septic tank?

A septic tank separates solids from liquid. GOV.UK describes solids settling while liquid leaves for further treatment through the ground. A tank alone is not proof that the discharge arrangements meet the rules.

• Find the system name on your service records or manufacturer manual.
• Ask the seller or service company where the liquid goes after it leaves the tank.

What is a treatment plant?

A small sewage treatment plant treats the liquid to a higher standard than a septic tank. In England, the surface-water guidance requires a small treatment plant for the watercourse route under the General Binding Rules. The permissions still depend on the site and discharge.

• Ask which model is installed and obtain its maintenance instructions.
• Ask what servicing and power arrangements that particular model needs.

What is a cesspit or cesspool?

A cesspool is sealed storage. It does not provide an outlet for effluent; collected waste is removed by tanker. In England it must be emptied regularly and must not leak or overflow. Do not apply a septic-tank desludging interval to sealed storage.

• Ask for the tank capacity, last emptying record and the firm that removes its contents.

Choose a system with the site in mind

• Which nation is the property in? Use that nation’s regulator guidance.
• Can a public sewer connection be considered? Ask the relevant water company and regulator.
• What ground or surface-water discharge route is proposed?
• What permissions, survey work and ongoing maintenance will the specific proposal require?
• Do not buy equipment solely because a product name appears suitable. Ask the installer to explain the whole proposed system.