The GRAF One2Clean Xtra 12 Person Sewage Treatment Plant sits in an 8,500 litre Carat XL tank. It suits two homes on a shared plant, a small guest house or a farm with staff housing.
On shared systems, the clear readouts on the Xtra panel help everyone see that the plant is working properly, so servicing is easier to arrange.
How the One2Clean Xtra Plant Works
The One2Clean Xtra 12 Person Sewage Treatment Plant treats wastewater in one tank using a simple three-stage cycle. First, sewage flows straight into the biological zone, with no pumping, and air flows through the whole tank so that bacteria start breaking down the waste.
Next, the control unit stops the air and the activated sludge settles to the bottom, leaving a layer of clear water on top. Finally, a one-piece clear water lifter draws off the treated water and the cycle starts again.
There are no pumps, moving parts or electrical parts inside the tank. Instead, the compressor and control unit sit above ground, where they are easy to reach for servicing. As a result, there is very little in the wastewater that can wear out or fail.
Key Features
- Very low energy use, from 0.63 kWh per day
- No pumps, moving parts or electrics in the tank
- Tested effluent quality of 7 mg/l BOD, 14 mg/l suspended solids and 0.5 mg/l ammonia
- Advanced control panel with clearer performance information and optional extras
- Sludge removal pipe available, so desludging does not disturb the internal parts
- Lightweight Carat tank, easy to lift into place without a crane
What’s Included
- 8,500 litre GRAF Carat XL underground tank with internal treatment parts fitted
- Clear water lifter and aeration system
- Air compressor and control unit
- Mini dome shaft with 150kg pedestrian telescopic lid
Options
- Traffic Telescopic Lid 3.5 Tonne, for driveways and parking areas
- External Cabinet M, for the control unit and compressor when there is no garage or outbuilding to house them
In addition, a raised outlet (fitted before dispatch), a warning beacon and a high level alarm are available on request. Please call us to add any of these to your order.
Where Can the Treated Water Go?
Treated water from the plant can usually discharge to a drainage field or, in many cases, to a ditch or stream. In England, the General Binding Rules set out when you can do this without a permit, so check the rules for your site or speak to the Environment Agency before you order. In Scotland, Wales and Northern Ireland, the local environment regulator sets the rules.
Specification
- Population: up to 12 people
- Tank: 8,500 litre GRAF Carat XL
- Dimensions: 3500 x 2040 x 2515 mm (L x W x H)
- Weight: 380 kg
- Loading: Pedestrian as standard, vehicle with the traffic lid
- Tank warranty: 15 years, with a 50 year design life
- Parts warranty: 1 year from commissioning, or 3 years with an annual service
- Manufacturer: GRAF UK
Commissioning and Delivery
A GRAF-accredited engineer commissions the plant free of charge once it is installed, which also starts the warranty. We deliver the One2Clean Xtra 12 Person Sewage Treatment Plant free to UK mainland addresses. However, the plant arrives on a lorry, so you will need to be able to offload it on arrival. You can also download the drawing, data sheet and installation manual from this page.








