This is a question we are asked Daily,
As suppliers of both, ie.The Eurotank range of Precast Concrete and Plastic/Grp tanks or Wastewater Treatment Systems and Septic tanks it is my honest opinion that it is a case of Horses for courses.
Undoubtably Concrete is the safer choice, reducing the fear of tank failure but on the other hand plastic units mostly do the same job and represent better value , ussually a saving of up to €1000 in some cases.
Plastic units are most suited where ground conditions are good. Soil structures that are loose , (not blocky heavy clay),stable (will not exert side pressure on the unit) but most importantly not wet. High water table increases buoyancy pressure under the tank which can result in the tank rising out of the ground if not properly anchored , this has even happened to tanks after emptying or desludging. In cases where the invert level is low ie. the foul water pipe from the dwelling is low in the ground resulting in the unit now being placed deep in the ground may not suit plastic units as ground pressure increases. However alot of these can be mostly overcome by the use of concrete backfill. Most manufacturers will insist on concrete backfill for all installations.This adds at least €400 to the cost which reduces the saving considerably.
Concrete units are more expensive mostly due to delivery costs requiring heavy machinery, but in bad conditions as described above may be necassary. They also mostly have bigger primary chambers which should mean longer desludge periods.If pumped distribution pipe network system is prescribed for the percolation area the Concrete Wastewater Treatment System will have a bigger pump chamber to supply this , plastic units will need seperate pump chambers again adding to the cost.
In Summary; If ground condition are good, low water table, the tank is not to be too deep in the ground plastic units are a safe choice and savings will be made. If conditions are marginal concrete backfill may be required, if conditions are bad a concrete unit is the safest and probably the most economical solution.
Tpw Systems ltd offer both with Our Eurotank Range of Wastewater Treatment Sytems and we would gladly site visit and give advice on suitability of either option with costings.
The Biocell range of plastic units we supply are the most robust available on the Irish Market. Is is Cylindrical shaped and sits in the ground on its end ( akin to a coke can sitting on a table ) most other units sit on their side this increases downward soil pressure on the the unit.
But we have recently Introduced our Eurotank Biocell with Concrete — This is the same as our Eurotank Biocell En certified Plastic GRP unit but with precast moulded on concrete base and skirt giving massive strenght to the unit but still having the fantasticinstallation benefits of a plastic unit. This is new technology on the market . It is a single unit weighing around 1.5 tonne can be handled by most diggers on-site.
Regardless of of the final choice it is of most importance that the installation is carried out by installers who have relevant experience, this we can also offer along with installation of the percolation area etc.
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