My septic tank is flooding?

There are many reasons which may cause a septic tank to flood and these can range from something as simple as an outlet ‘dip pipe’ being blocked to more serious problems involving the receiving soakaway system.

The effluent level inside a septic tank should be at the level of the outlet pipe.  In some instances either the inlet or outlet pipes for a septic tank can become blocked with materials such as fat or tissue.  If the inlet ‘dip pipe’ becomes blocked this would result in the foul drainage to the tank flooding, and this is more common in older traditionally built septic tanks.  If the outlet ‘dip pipe’ becomes blocked this would result in both the septic tank and incoming foul drainage pipe work flooding.  In some cases it is only necessary to clear the blockage with drainage rods.

The most common cause for a septic tank flooding is due to the receiving soakaway and not the septic tank.  If a soakaway fails and prevents the effluent from percolating through the ground this will result in the soakaway, septic tank and the foul drainage pipe work surcharging. In some cases having a soakaway ‘jetted’ can resolve the failure of a soakaway, but in our experience it is often necessary to have the soakaway replaced.

If you are having problems with your septic tank or soakaway, call our team today to find out how we can help on 01255 853890 or complete the form below.

Sewage Treatment Plant Installation in Norfolk – National Trust

Sewage treatment plants offer Norfolk homeowners with a modern alternative to septic tank systems for areas not serviced by mains drainage. As leading independent installers and service providers for sewage treatment plants in Norfolk, Mantair is ideally placed to provide Norfolk homeowners with a sewage treatment plant to meet their site requirements, or provide the expertise required for assessing septic tank problems.

sewage treatment plant norfolk

Burnham Overy Tower Windmill in Norfolk was built in 1816 for Edmund Savory, a miller who was running a watermill on the River Burn known as the Lower Mill.  Savory worked this mill in Norfolk until his death on 9th February 1827, when it passed to his son John.  The mill was given to the National Trust in 1958 and has been converted to holiday accommodation.

The National Trust contacted Mantair with a view to installing a domestic sewage treatment plant to solve the septic tank problems at the property.  The project included the design and installation of an appropriate packaged sewage treatment plant with pumped outlet to facilitate the foul water drainage on site.  Prior to the design element of the project, Mantair carried out a full site investigation including a detailed survey of the existing drainage and underground services.

On sizing the new sewage treatment plant it was necessary to install an 18 population equivalent Tricel treatment plant to cope with the flow and strength of sewage the system would receive.

sewage treatment plant norfolk installseptic-tank-problems-norfolksewage-treatment-plants-norfolk

During the design stages of the project, Mantair liaised with the Environment Agency to determine the point of discharge for the overflow from the system.  Due to site levels it was necessary to have a pumped outlet on the Tricel sewage treatment system to enable the treated effluent to be discharged to the agreed outlet point.  With the sewage treatment plant having an integral pump Mantair installed a high level alarm and beacon with back-up battery to provide instant warning of power failure.

As with all underground septic tank and sewage treatment plant installations Mantair carries out, the tank was completely encased in concrete to ensure the structural integrity of the tank is not impaired and to prevent the potential of flotation of the tank.

The scope of the installation works included:
  • Exposing the existing foul drainage pipework and installation of new drainage to the Tricel sewage treatment plant;
  • Complete installation of the Tricel treatment plant in a suitably sized excavation and backfill;
  • Installing a MEDO air blower within an existing outbuilding and provision of an RCD protected power supply;
  • Installation of the air main from the MEDO air blower to the Tricel sewage treatment plant;
  • Installation of the pumping main from the Tricel system to the point of discharge, including for the installation of an inspection chamber.

On completion of the ancillary works, we commissioned the Tricel sewage treatment plant, including setting of air valves, checking all pipe work joints and viewing the discharge into the final discharge chamber.

During the project Mantair engineers took all the necessary measures to ensure minimal disruption to the property and its surroundings.

Mantair provides a comprehensive septic tank and sewage treatment plant service throughout Norfolk. This includes free site inspections, guidance and advice on the most suitable system for our client’s requirements, complete installation, commissioning and full after sales care.

If you would like a Mantair engineer to visit you please fill out the form below or contact us on 01255 853890.


Septic tank conversion system installation in Essex.


Mantair was contacted by the owner of a property regarding the problems they were experiencing with their septic tank system.  The property is located on the outskirts of Brentwood in Essex.

On inspection of the drainage arrangements it was found that the property drained to a septic tank located in the rear garden of the property.  On internal inspection of the septic tank it was evident that a submersible pump had been installed within the tank with the sewage effluent being pumped directly to a boundary ditch.  It transpired that the previous owners of the property had installed the pump due to the septic tank soakaway failing.

On further inspection it was found that the existing septic tank was in good structural condition but there was insufficient land available for the construction of a new soakaway.   It was therefore necessary for a sewage treatment system to be installed which would produce a treated effluent suitable for discharge to the boundary ditch.

With the existing septic tank being in good structural condition and sufficient capacity Mantair recommended the installation of a septic tank conversion system.  The Mantair conversion unit is specifically designed to fit within an existing septic tank or cesspool, effectively ‘converting’ the existing tank into a small sewage treatment plant.  The treated effluent produced from the Mantair unit complies with the requirements of the Environment Agency for discharge to a natural watercourse.

To minimise the disturbance to the garden the existing pumping main was reused with a new pumping station being installed and connected at the ‘head’ of the pumping main.  The air blower for the Mantair septic tank conversion unit was positioned within a Beehive blower housing – a purpose built housing designed to blend into the garden setting.


Prior to any works commencing Mantair obtain a Permit from the Environment Agency for the discharge to the boundary ditch.

As with the majority of Mantair septic tank conversion system installations, the disturbance to the garden was minimal with substantial cost savings when compared to the installation of a packaged sewage treatment plant.

Mantair provides a comprehensive septic tank and sewage treatment plant service throughout the majority of the UK. This includes free site inspections, guidance and advice on the most suitable system for the client’s requirements, complete installation, commissioning and full after sales care.

If you would like a Mantair engineer to visit you regarding a septic tank conversion system or sewage treatment plant installation, please fill out the form below or contact us on 01255 853890.


Potential problems for Septic Tanks

Excessive draining of cooking oils and grease can cause the inlet drains to block.  Oils and grease are difficult to degrade and can cause difficulties with the emptying.

Disposing of non-biodegradable items such as nappies and baby wipes will rapidly clog the septic tank and these items should not be discharged to the tank at any point.

Certain chemicals should not be discharged to septic tanks, including pesticides, herbicides, paint, solvents or high levels of bleach.

Septic tank failure signs

  • Drain or sewage backup;
  • Discharge of effluent to surface or watercourse;
  • Effluent level above the septic tank inlet;
  • Septic tank being emptied frequently;
  • Depression area over the septic tank or soakaway.

Sodium Binding

Excessive use of detergent based products i.e. dishwasher tablets, washing powders etc. will lead to eventual failure of the soakaway.  This is caused by a process called sodium binding where the sodium present in detergents cause any silt or clay particles in the sub soil to bind together to form am impervious layer.  The same effect occurs if a water softener is present as the softened water will have relatively high sodium content.

Increase in Flow

Additional waste water entering the septic tank.  A septic tank and the receiving drainage field / soakaway are designed to cater for a certain volume of flow per day.  If the flow being discharged to a septic tank increases and the tank is not designed for this additional flow then problems can be experienced with both the septic tank and drainage field / soakaway system.

Physical Damage

Physical damage to the drainage field / soakaway.  In some cases a septic tank can flood due to the receiving soakaway pipe work becoming damaged and broken.  This can often be due to heavy machinery moving over the soakaway and crushing the pipes.  Older ‘but-jointing’ soakaway systems were constructed using clay wear pipes and it is common for these clay wear pipes to become dislodged due to ground movement, resulting in soil entering the pipe work and blocking the soakaway.

Root Ingress

The drainage field / soakaway being constructed in close proximity to trees and shrubs.  Roots of trees and shrubs planted too close to a drainage field / soakaway can enter the drainage pipe work and block the pipes.  Root ingress into drainage fields / soakaways is the cause of many systems blocking and as a result flooding of the septic tank system.

Mantair works in partnership with the UK’s leading drainage insurance claims management company to offer our customers a unique insurance claims management service. Providing expertise in managing insurance claims for the costs of repairing or replacing damaged drainage systems, we work on behalf of property owners helping them to save thousands of pounds in resolving their septic tank problems.

Naturally High Water Table

The drainage field / soakaway being under the natural water table.  This can often be the cause for septic tank soakaway systems failing during winter months only.  When a drainage field / soakaway is operating underneath the natural water table the septic tank, soakaway and foul drainage pipework will be at the same level as the surrounding water table and as a result the flooding within the system can be moderate or severe.

Problems with septic tank systems operating in high water table areas can be overcome by installing a Mantair septic tank conversion system.