Septic Tank - Sewage Treatment System - COSTS

Why septic tank systems are no longer the cheapest option

Soakaway Drainage FieldIn the past, septic tanks were the cheapest option for off-mains sewage treatment, because there was no regulation on the design of the soakaway. This is no longer the case, due to new Soakaway Drainfield Regulations. The rules mean that soakaway drainfields cost Thousands more than a sewage treatment plant system, if you have a ditch or other watercourse within reach.

A Typical Drainfield will need over 100 metres of slotted pipework and over 30 tonnes of expensive, washed drainage stone. 

There is a huge difference in the purchase prices, installation and running costs of different sewage systems as shown on this page.

Click on this link to compare the performance of different sewage treatment plants.

Cost of a CESSPOOL (or CESSPIT as it is often called)

This is the most expensive tank to install, as they are massive. They are also the most expensive system to run. Every litre that goes into it has to be removed by tanker as it is a sealed tank. They are banned in Scotland.Cesspool

Typical Costs for a single 3 bed  house
  • Tank Cost = £3500  (35,000 litres)
  • Installation Cost = £6500 
  • TOTAL COST = £10,000

Typical Maintenance Costs (Emptying only is required)

  • Average family of 4 persons x 200 litres per day = 800 litres per day volume discharged.
  • Min. tank capacity = 18,000 litres Storage capacity = 18000 / 800 = 22.5 days
  • Therefore tank will require emptying - 365 / 22.5 = 16.2 times per year
  • With an average emptying cost of around £180 per 4500 litres, a complete emptying of 18000 litres will cost £720, 16 times a year 
  • Average annual cost = £11,520 per year

Cost of a SEPTIC TANK 

This is the most expensive complete system to install and is also costly to run, as the drainfield will clog within a few years and has to be replaced. Septic Tanks are now banned in most areas of the UK due to pollution factors and under the Environment Agency General Binding Rules.conical septic tank

Typical Costs for a single house:

  • Tank Cost = £790 (larger tanks cost more)
  • Installation Cost = £1500
  • Soakaway system (assuming 100 metres of drains) = £5200
  • TOTAL COST = £7490.00

Typical Maintenance Costs

  • Emptying once per year = £150 per year
  • Percentage cost of replacement soakaway (every 10 years average ) =£520
  • Average annual cost = £670.00

The Environment Agency has confirmed to us that soakaway crates are NOT acceptable for foul water soakaways as they do not conform to the Building Regulations or the BS 6297 2008. Crates are only allowed for rainwater soakaways. If you find a company selling then for foul water soakaways, report them to Trading Standards.

If a septic tank and land drainage system are unable to treat the sewage, then one of the following sewage treatment systems must be used to remove a substantial amount of the pollution contained in the wastewater and protect our environment.

Cost of a TRADITIONAL SEWAGE TREATMENT PLANT Falcon_Cross Section

Not always the best choice.

Typical Costs for a single house
  • Plant Cost = £1800 to £3200
  • Installation Cost = £2000 to £3000+ (depending on the model.)
  • Land drainage system (assuming 100 metres of drains) = £5200 or £200 typical cost if to a ditch with a 10 metre pipe run
  • TOTAL COST = £4000 to £11,400+

Typical Maintenance Costs

  • Emptying (either annually, 6 monthly, or 3 monthly (depending on the make) £100 to £400 per year
  • Power consumption = £80 to £180 per year  (depending on the model)
  • Maintenance Service = £100 to £375 (depending on unit chosen) per year
  • Average annual cost = £285 to £955 per year

Cost of a MODERN 'extended aeration' or 'activated sludge' SEWAGE TREATMENT PLANTVortex Sewage Treatment Plant (1)

Cost effective sewage treatment plants - cheap to install and run, depending on the model.

Typical Costs for a single house
  • Plant Cost = £1850 to £2400
  • Installation cost = £600 (DIY) to £3000
  • Drainage system to Ditch = £25.00/metre of drain run
  • TOTAL COST  £2260 to £5400

Typical Maintenance Costs

  • Emptying = £100.00/year
  • Power consumption = £25 to £180/year (depending on the model - the VORTEX is the cheapest)
  • Maintenance Service = £100 to £130 (depending on the model)
  • Average annual cost = £225.00 to £410.00 per year

Cost of a FILTER SEWAGE TREATMENT PLANTFilterpod sewage treatment plant

No Electricity

Typical Costs for a single house start at

  • Plant Cost  = £2500
  • Installation cost = £2000 to £4000
  • Drainage system to Ditch = £20.00/metre of drain run
  • TOTAL COST  £4500 to £7500

Typical Maintenance Costs

  • Emptying once every year = £100.00/year
  • Power consumption = £0
  • Maintenance Service = £100.00
  • Replacement Filter Bags = £50
  • Average annual cost = £250.00 per year

Cost of REED BED sewage treatmentreed bed

VERY expensive to run.

Typical Installation Costs

  • Septic tank installed price £2250
  • Total supply and Installation Cost = £ 8500 (including power supply etc.)
  • Land drainage system (assuming 100 metres of drains) = £ 5200 (or this may be a reduced cost if using an outfall pipe to a stream if the reed bed is used as a tertiary treatment after a sewage treatment plant)
  • TOTAL COST = £15,950 (Note - there may be a cost for the larger area of land required)

Typical Maintenance Costs

  • Emptying of tank once per year = £180 per year
  • Power consumption of the pumps = £290 per year
  • Maintenance = reed harvesting/composting/replanting (4 days work) = £450
  • Total reedbed replacement required every 10 years (Aston University Research for Severn Trent Water Authority) 
  • TOTAL COST = £2515 per year