Emptying
| Who | Price | Source |
|---|---|---|
| Scotland: Scottish Water household de-sludge, up to 9 m³ (2026–27) | £254.40 scheduled; £353.10 unscheduled; £509.70 urgent | Scottish Water |
| Northern Ireland: NI Water domestic desludge, up to 4.5 m³ (2026–27) | one free discretionary empty in any 12-month period, if NI Water's service conditions are met; then £108 (£142 for difficult access) | NI Water; NI Water |
| England example: South East Tankers, Sussex (prices correct from 6 September 2024) | £170 for up to 1,000 gallons, rising to £380 for up to 4,000 gallons, for the first hour on site | South East Tankers |
| Wales examples: private tanker firms (checked 31 October 2026) | CRES Tanker Services (Carmarthenshire, Pembrokeshire and Ceredigion) advertises empties from £130; AE & AT Lewis (Anglesey) lists residential empties at £185–£580 | CRES Tanker Services; AE & AT Lewis |
Replacing or installing a septic tank
| Item | Typical cost | Source |
|---|---|---|
| Septic tank unit only, about 2,800–3,100 litres (5–6 people). Equipment only: no delivery offload, excavation or installation. | about £1,180–£1,220 inc VAT | Clarkes of Walsham; Tanks For Everything, Oct 2026 |
| Larger septic tank unit only, 5,000 litres. Equipment only. | about £1,890 inc VAT | Tanks For Everything, Oct 2026 |
| Like-for-like tank replacement, supplied and installed, where the existing drainage field can be kept | roughly £3,000–£7,000 | Alton Facility Services; Clear Stream Drainage Solutions |
| New drainage field (sized from a percolation test), supplied and installed | £3,000–£7,000; one installer advertises from £3,500 (1–3 bed) and from £4,500 (4+ bed) | Clear Stream Drainage Solutions; Fastfix Drainage & Plumbing |
| Percolation test | around £300–£500 | Clear Stream Drainage Solutions |
| New septic tank with a drainage field, supplied and installed | from about £5,500 on a straightforward site; commonly £5,000–£15,000 | Fastfix Drainage & Plumbing; Clear Stream Drainage Solutions |
| Complex site (granite bedrock, restricted access or a high water table) | £12,000–£20,000+ | Clear Stream Drainage Solutions |
Sewage treatment plants
| Item | Typical cost | Source |
|---|---|---|
| 6–7 person treatment plant, unit only: Marsh Ensign, Tricel Novo UK6, Graf One2Clean 7PE. Equipment only: excludes installation. | about £2,190–£2,700 inc VAT | Cotterill Civils; Tanks For Everything; Tanks For Everything, Oct 2026 |
| Premium 6-person unit: Klargester BioDisc BA. Equipment only. | about £4,950 inc VAT | Tanks Direct, Oct 2026 |
| Manufacturer's guide for the unit only | £1,700–£3,000 (6-person), £1,900–£3,500 (8-person) | Tricel |
| Installation on top of the unit (delivery, excavation, groundwork) | £2,000–£8,000, depending on size and ground | Tricel |
| Supplied and installed, typical domestic job | commonly £7,500–£15,000; difficult sites cost more | Fastfix Drainage & Plumbing; Alton Facility Services; The Sewage Guy |
| Annual service | about £100–£300 a year, plus any parts | Alton Facility Services; Fastfix Drainage & Plumbing; Tricel |
Upgrading a tank that discharges to a ditch or stream (England)
| Option | Typical cost | Source |
|---|---|---|
| Add-on conversion unit fitted after the existing tank (Marsh Uni:Gem, certified to EN 12566-6). Equipment only. | about £2,390 inc VAT for the 6-person unit for round septic tanks (Build & Plumb). BPPlastics lists a Uni:Gem at £3,009.60 inc VAT but doesn't state the model size. | Build & Plumb; BPPlastics, Oct 2026 |
| Conversion, supplied and installed | typically around £5,000 + VAT | The Sewage Guy |
| Replacing the septic tank with a new treatment plant | commonly £7,500–£15,000 | Fastfix Drainage & Plumbing; Alton Facility Services; The Sewage Guy |
| Keeping the tank but discharging to ground through a new drainage field instead | £3,000–£7,000 for the field | Clear Stream Drainage Solutions; Fastfix Drainage & Plumbing |
In-tank retrofit kits installed after 2007 need an Environment Agency permit. Add-on units need EN 12566-6 certification to discharge to surface water without one (GOV.UK; WTE).
For a deeper look at septic tanks, visit our sister site septictankquotes.co.uk or our septic tank service page.
Frequently asked questions
How much does it cost to empty a septic tank?
Scottish Water charges £254.40 for a scheduled household de-sludge (2026–27). NI Water offers one free discretionary empty a year if its conditions are met, then £108. Private tanker firms in England and Wales set their own prices, from about £130 to £580 in the examples we list.
How much does a new sewage treatment plant cost?
Units cost about £2,190–£2,700 inc VAT from merchants. Supplied and installed, installers commonly quote £7,500–£15,000.