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Home > Septic Tanks - Standard and Flatbed > Spherical & Onion Shaped Septic Tanks

Onion Shape & Spherical Septic Tanks

Onion shaped spherical septic tanks are an ideal wastewater management tool in areas where there is no hard rock or high water table. This allows for greater excavation to position the septic tank with its increased height. Onion shaped septic tanks are easy to install and maintain. They are made up of two or more chambers in which raw sewage is treated through anaerobic digestion.

The effluent is then allowed to escape into a percolation pit in the ground, where the soil completes the treatment process. Solid sludge that remains in the primary settlement chamber is then removed from time to time and sent to a treatment facility. This prevents it from clogging the soak pit and preventing the bio digestion of waste. 

Onion shaped septic tanks can further be fitted with an optional tank filter to reduce suspended waste in the effluent. This prevents odours and improves the quality of the effluent, prolonging the life of the percolation pit. 

MP Tank Suppliers are top suppliers of high quality Glass Reinforced Plastic septic tanks. These are ideal for use in both domestic and commercial applications. GRP septic tanks are made from glass and 100% virgin resin with no chalk fillers. This is the perfect material for constructing a tough, long lasting and maintenance free septic tank. 

Benefits of MP Suppliers onion shaped septic tanks

Our onion shaped septic tanks are much more durable and longer lasting than traditional concrete and steel tanks. Unlike them, GRP tanks do not rust or corrode, and are resistant to long exposure to chemicals and gases in raw sewage. They are also easy to install because unlike concrete or steel, they do not require a lot of excavation or mortar.

Other benefits include:

•Light and easy to transport and install, which saves upfront costs
•Tough, durable and resistant to shock and impact
•Protective shell to withstand any type of ground conditions
•Lifting eyes and keying-in lips for easy positioning and installation 
•Require little maintenance over their long lifespan
•Simple and cheap to repair
•Cannot be penetrated by tree roots
•Standard pedestrian frame and cover
•Easy to convert into a treatment plant with an optional conversion unit


Onion shaped septic tank specifications

MP Tank Suppliers stock onion shaped septic tanks in a number of sizes and dimensions to suit every requirement. They are available in three capacities of 2800L, 3800L and 4500L. These sizes also cater for domestic requirements, which have to be 2700L for 4 dwellers, with an extra 150L for every additional occupant. 

Each of these septic tanks has a flat bottom for stability and easy installation, and come with the following specifications:

•110mm inlet and outlet diameter
•1000mm inlet invert distance
•1075 outlet invert distance 


•2800L (2780 h x 1870mm)
•3800L (3000 h x 2075mm)
•4500L (3100 h x 2196 mm)

As leading suppliers of onion shaped septic tanks, MP Tank Suppliers ensure that every tank is made from the highest quality materials and the best finishes. All our products are tested and certified to British Standards BSEN12566:1 and ISO certification. They meet all health, safety and building regulations. 

We boast of an extensive distribution network which can deliver your domestic or commercial order within 4 days. Our stocks are maintained at high levels to ensure that we honour any order without delay. We also offer all our customers great technical support and advice.

Call us today on 0333 456 6702 to place your order or to get more information on any of our products.