We have installed several hundred of these successfully for over fifteen years for our clients and found them to be extremely reliable.

The Mantair range of sewage treatment conversion units provide a discreet, reliable and cost effective solution to sewage treatment for domestic dwellings without mains drainage, but where an existing septic tank or cesspool is present.


There is a lifetime Process Guarantee provided by the manufacturer. Don't be misled by installers and manufacturers salesmen attempting to sell you an expensive Treatment Plant where one is not needed. The latest E.U. Standard for Treatment Plants applies to the tankage and so does not apply to any Conversion Unit and the Units are approved of by the Environment Agency. We can advise you on the current Environment Agency regulations, and obtain any necessary Permit for you (needed if discharging to a stream). If you are discharging from a MANTAIR converted septic tank to ground and the volume is less than 2 cubic metres per day then you are not obliged to register your discharge if you reside in England, although voluntary registration is free.

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o The most economically installed treatment system in the UK;
o Does not require the installation of any tankage, thus avoiding the  disturbance of established gardens;
o The treatment plant is completely hidden from view;
o Designed to produce an effluent in compliance with the Regulating Authorities;
o Peace of mind with a Lifetime Process Guarantee;
o The efficient air blower is both quiet and economical with low running costs;
o Integral surge control system;
o Works in high water table areas;
o Less than two hours maintenance a year;


Each Unit is purpose-built to suit the depth, diameter, invert depth and access shaft of the existing tank, so usually the unit can simply be dropped into place. An airline is taken from the tank to the site of the airblower, and an electric cable laid from this to the nearest suitable supply. Often the existing tank outlet drain can be used for the discharge. There is none of the disturbance and upheaval and destroyed gardens that is often associated with the installation of systems with their own tankage.


The MANTAIR system, like the majority of Package Treatment Plants now, is powered by a small air blower, which can be located up to 25 metres from the Mantair system. It is connected to the plant by a small bore MDPE pipe concealed underground. The blower provides the air that is required for the treatment process and to lift the treated effluent to the discharge point. We use MEDO air blowers which are well known to be the best and quietest on the market.

Sewage entering the tank discharges into the Aeration/Mixing Zone. Air is supplied to this zone via an aerator contained wimantair topthin a draught tube. Large and heavy solids are deposited in the Primary Settlement Zone.
The aeration and mixing encourages the growth of aerobic micro organisms which degrade the sewage.
The contents of this zone, where the micro organisms are maintained in suspension, is referred to as the 'mixed liquor'. As further flows enter the tank, mixed liquor is displaced into the Final Settlement Zone. Here the micro organisms separate and form a thin sludge. This is continuously returned to the aeration / mixing zone, thus maintaining the levels of micro organisms in the mixed liquor.
The liquid which remains in the final settlement zone is the treated effluent which is discharged from the system via the Final Effluent Airlift.
The final effluent airlift controls the rate of discharge from the system and prevents any shock hydraulic loads from affecting the treatment process. The use of an airlift enables the Mantair system to discharge the effluent at a higher level than the sewage inlet.


Maintenance of the Mantair system is simple, and comprises the renewal of the air blower inlet filter and the flushing through of pipe work and components. The tank will require emptying by tanker at about twelve month intervals. As with all Treatment Plants, regular maintenance is essential to ensure efficient operation.
The Mantair Conversion Unit is simpler to maintain than many other treatment plants as there are no electrical, mechanical or moving parts within the underground treatment zone.


European Standard EN12566-3

EN12566-3 is the European Standard for "packaged sewage treatment plants" up to 50 population equivalent. An integral part of the test procedure is structural testing of the packaged plant tankage. As the MANTAIR conversion unit does not include new tankage, it cannot be tested and EN12566-3 is not applicable. As there is not a European Standard for 'in tank' Conversion Units it is not possible for them to obtain a CE Mark. However, all components used in the manufacture of the MANTAIR conversion unit comply with the relevant European Standard. The Environment Agency recognises the MANTAIR conversion unit as a sewage treatment system and issues Permit Certificates authorising the discharge from the system to be direct to natural watercourses. The MANTAIR conversion unit should not be confused with other products marketed as 'conversion units' which involve the installation of additional tankage downstream of the existing septic tank. As new tankage is required these products can be tested under the European Standard. These products however do not 'convert' the existing septic tank, but provide biological treatment in additional tankage.


Mantair packaged plants and conversion units are designed to treat domestic sewage and to achieve a final effluent standard of 20mg/It B.0.D. and 30mg/It Suspended Solids.
The Mantair treatment plants and conversions units are available in five population sizes.

Max. No. of
Population Equivalent (P.E.)
Plant Size Required
B.O.D. Load

Air Blower Rating

1000 0.3 0.086
1400 0.42 0.086
2000 0.6 0.100
2400 0.72 0.130
3000 0.9 0.130
The above sizing criteria are based on:
a) all roof and surface water being excluded from the treatment system:
b) kitchen waste disposal units not being connected to the foul drainage system serving the treatment system,
For Multiple Properties first use the above chart to determine the population requirement for each property. Then add together the population requirements of each property to arrive at the population size required for a single system. For example, if a system is to serve two properties - one with 3 bedrooms and one with 5, the size required for a single system is therefore 5 + 7 = 12 P.E.

We have the years of experience needed to know if your tank is suitable for conversion, which is essential. If it is decided that it is not suitable we will be able to recommend an alternative solution for you as we are not tied to any particular manufacturer. Be assured we have a reputation for always advising our clients on the best system for them, not the most profitable for us!


Coleman Contractors, Mill Farm, Chalvington Road, Golden Cross, Hailsham, East Sussex, BN27 3ST
01825 872611 or 07778 664466