Installing Septic Tanks: Concrete Surround

Septic Tank Installation

Installing Septic Tank: Concrete Surround


Before installation commences Infinity Environmental plan excavation to meet health and safety requirements. To make sure the installation process is safe as possible the excavation might require shuttering or excavating at ‘safe’ angle.

Installing any type of septic tank we follow the manufactures minimum surround thickness. The excavation would have to take into account any shuttering used.

Different ground conditions can make huge impact on the size of the excavation. Stable ground condition such as clay would make installation dimensions standard, or over- excavation might be necessary e.g running sand.

Buoyancy and Anchoring

The dimension of concrete surround can differ from manufactures specification if septic tanks are installed in high water table area. Our team can advise on installation the additional thickness of concrete surround based upon the flotation factor and mass concrete density.

Type of Concrete

The type of concrete mix to surround the tank is based upon the manufactures specifications and site conditions. The amount of concrete required is based upon the size of the tank and site conditions determining the size of the excavation.

In good ground conditions, we recommend 28 day compression strength of 20 to 30 N/mm2 with 50mm slump, complying to the relevant BS EN standard. If ground conditions are not suitable for the standard concrete mix our specialists will take into account aggressive soil types, structural applications, and calculate the right mix for your installation.

Impact of Concrete on Back Filling the Tank

On back filling the tank with concrete the discharge impacts are considerable. The impact of concrete back fill must not exceed 15 KN/M2 on the septic tank commonly known as ‘Vessel’. Under no circumstances should concrete be discharged directly onto the tank.

Our Installation Service

All our septic tank installation for underground tanks only use concrete back fill. Please contact the specialist to ensure your installation is a success.