Off-mains drainage costs vary a lot with your property, so treat these as ballpark ranges — then get a quote for the real figure. Our cost calculator gives you an instant estimate.

Emptying

The routine cost most homeowners face. For a typical domestic tank, expect a few hundred pounds per visit — usually somewhere around £180–£320 depending on tank size and how easily the tanker can reach it. Remote or awkward-access properties cost a little more because the tanker has to work harder.

Most family tanks need emptying roughly once a year — see how often to empty.

New septic tank installation

A new septic tank with its drainage field typically runs £4,500–£8,500 for an average home, more for larger properties or difficult ground. The drainage field is often the variable part — soil that drains poorly needs a bigger, more expensive field.

Sewage treatment plant installation

A packaged treatment plant costs more than a septic tank — usually £8,000–£15,000+ installed — because the unit itself is more sophisticated and needs power and servicing. It’s the common choice when a septic tank can’t legally be used.

Replacement / upgrade

Replacing a failing or non-compliant septic tank — including the 2020-rules upgrades — typically lands in the £6,000–£12,000 range, depending on whether you go to a treatment plant or add a drainage field, and how much old kit has to come out.

Drainage field / soakaway

A new or replacement drainage field on its own is often £3,500–£7,000, driven mainly by ground conditions and the size the soil requires.

What moves the price

• Access — can a tanker or digger get close, or is it a long, tight or remote approach?
• Property size — more bedrooms means more capacity and a bigger system.
• Ground conditions — soil type and water table strongly affect drainage-field cost.
• Permits and sensitive locations — a Source Protection Zone or a large discharge can require a permit.

For a figure tailored to your property, use the cost calculator or call us for a firm quote.