Allerton Systems


Consept system

The Allerton Consept is a septic tank conversion unit, which will convert your septic tank into a small package treatment plant.
It is designed in accordance with the British Standard BS6297:1983 - Design and Installation of Small Sewage Treatment Works.
The unit can convert a wide range of septic tanks and cesspools, both GRP and traditional brick built.

ConSept system

ConSept in traditional concrete and brick built septic tank

Consept system

ConSept in a prefabricated glass fibre septic tank

How it works:

Raw sewage gravitates into the septic tank/cesspool and is then aerated by air released from the bubble diffuser that rises up the distributor tube into the aeration zone. The sewage is completely mixed with the oxygen, which allows the growth of aerobic organisms that break down the wastewater contaminants, by biological action. The air required for the process is provided by an air pump that is located in an adjacent shed or garage or within a purpose built GRP housing. As raw sewage enters the tank, this displaces treated effluent from the aeration zone to the final settlement zone. The treated effluent flows slowly up through the final settlement zone until it reaches the discharge point. The final effluent is discharged via the outlet syphon where it is lifted and flows to the discharge point, which can be at ground level. The discharge flow is controlled with a uni-directional flow regulator.


Utilises your existing septic tank or cesspit. This allows for a quicker installation with less disruption to your garden and of course saves you money!
Fits inside the septic tank. Unobtrusive and quiet in operation.
Manufactured using composite material and non-ferrous fixings to stop corrosion and ensure a long and trouble free life.

Technical specification:

Population equivalent: 1 to 6 Maximum daily
BOD loading: 360g Per Day
Maximum inflow: 1200 litres per day
Final effluent quality: 20:30 BOD:SS



The Allerton biofilter is a compact, highly efficient, self-contained anaerobic treatment plant which acts like a septic tank but doesn't need a leaching bed. The biofilter treats the effluent, dramatically reducing the BOD and suspended solids prior to discharge, typically giving a 90% reduction to a BOD of only 20mg/l – the equivalent of rain water. Our range of biofilters are designed to consistently achieve these levels in all types of soil conditions.


Midi Range 15PE - 30PE : Maxi Range 41PE - 180PE

How it works:

The Biofilter works in conjunction with a Primary Settlement Tank. From here partially treated effluent enters the baffle zone where an irrigation pump is used to spray the liquid over the media via the distribution system. This process is repeated until eventually the effluent is allowed to settle in the final settlement zone from where it is discharged at a standard to satisfy the Environment Agency.

A secondary sludge return pump periodically removes dead bacteria by returning it to the primary settlement, tank, where it is stored until removed by tanker.

10 good reasons:

1. Very competitively priced. Probably the most realistically priced unit on the market.

2. Designed to BS 6297 - Designed and Installation of small sewage treatment works.

3. Constructed of high quality Glass Fibre.

4. Superior Grundfos pumps and efficient random media.

5. Single phase.

6. 3 year warranty on working parts.

7. Simple installation - the unit has a holding down plate at the base.

8. Commissioning service.

9. Sample Chamber, Grease Trap and Pump Station optional extras if required.

10. Electric cable and pressure pipe can also be supplied.

Midi System  
Sewage treatment plant
  1. Fan Housing
  2. Distributor
  3. Media
  4. Outlet
  5. Irrigation Pump
  6. Baffle Zone
  7. Secondary Sludge Return Pump
  8. Sludge Return Pipe
  9. Inlet

sewage treatment plant

Midi System Dimensions








15 1500 1450 2900 1800


20 1500 1450 2900 1800


25 1500 1450 3150 1800


30 1500 1450 3400 1800


Maxi System  
septic tank conversion
  1. Fan Housing
  2. Media
  3. Outlet
  4. Baffle Zone
  5. Irrigation Pump
  6. Sump
  7. Secondary Sludge Return Pump
  8. Filter Shell
  9. Distributors
  10. Sludge Returns Pipe
  11. Inlet

Allerton Maxi range

Maxi System Dimensions










41 2200 1200 4200 2200 1950 1900


54 2200 2700 4200 2200 1950 1900


65 2200 3200 4200 2200 1950 1900


80 2200 3700 4200 2200 1950 1900


115 3200 3200 4800 3000 2050 2000


135 3200 3200 4800 3000 2050 2000


160 3200 3700 4800 3000 2050 2000


160 3200 4200 4800 3000 2050 2000



BOD = Biochemical oxygen demand is the most widely used test to determine whether a particular system is working properly. BOD measures the amount of dissolved oxygen used by microorganisms in the oxidation of organic matter in sewage.


POPULATION EQUIVALENT = Population equivalent refers to the amount of oxygen demanding substances whose oxygen consumption during biodegradation equals the average oxygen demand of the waste water produced by one person. For practical calculations, it is assumed that one unit equals 54 grams of BOD per 24 hours.

Mark Watts Drainage is a Sussex based company. We are happy to undertake work in Kent, Sussex and Surrey.

Please call us or email us using the contact page for a site inspection and quotation.

Phone: 01273 812 331

Mobile: 07990 553 747



























Why Choose a Biofilter?

Advantages and benefits:

Biofilters produce the required standard of effluent for a ditch or watercourse.
No problematic leaching bed required and no contamination of subsoil.

No extensive ground or tree clearance required for leaching beds.
Less costly ground works and low environmental impact.

Kinder to the environment.
Much less disruption to property owners and little disturbance to the surrounding environment and landscaping.

Reliable and low maintenance with long life filter media and easily replaceable pumps. Rigorously tested and approved in the UK, with a proven track record over 17 years.
Peace of mind for property owners.

Effluent can be discharged uphill using pumped outlet if required.
Awkward hillside builds become possible. Most areas can be developed.

Compact design.
Existing problems in communities where effluent drains into ditches and rivers can now be cured.

No leaching bed.
Biofilters are effective on difficult build sites featuring heavy clay soil, shallow or exposed bedrock.

Sprayed water within the system collects gases in the air.
No nasty smells.