Septic Tank FAQs
What size tank do I need form my application?
Septic tanks should have a capacity below the level of the inlet for up to 2,700ltrs for 4 users. This size should be increased by 180ltrs for each additional user. Top
What are the physical dimensions of the unit?
Refer to the appropriate drawings. Top
How big does my drainage field need to be?
This is dependent on the porosity of the soil. Porosity tests should be completed to establish the soil characteristics and these results then used within a basic calculation.
A = Vp x P x 0.2. where A = the plan area of the soakaway system, Vp = the seconds per millimeter (results from the percolation test) and P = population using the system.
The result of this calculation will provide an area in m². This will then be converted into the length of the slotted/perforated pipe-work within a soakaway system.
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How far does the unit need to be away from my property?
Minimum of 7.0m from any habitable parts of the building. Top
How far can my soak away be from a watercourse?
At least 10m form any watercourse or permeable drain. In addition to this, the soakaway should be at least 50m from any point of abstraction of any groundwater supply and not in any ‘zone 1’ ground water protection zone. Please refer to the EA for confirmation as to whether the site meets the requirements. Top
How does the septic tank work?
The tank is typically split into two basic chambers. The sewage enters the first in which the solid matter either settles to the bottom of the tank or rises to the top forming a crust. The liquid within the area between these zones is decanted into the second chamber area, passing through a baffle system. From this secondary zone, the settled effluent decants out of the outlet.
They should only be used in conjunction with a suitably sized soakaway.
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Do I need consent from local authorities to install this unit?
Generally a ‘Limited Discharge Prohibition Notice’ is the only requirement, issued by the EA, these stipulate that the site is prohibited from discharging in excess or ‘X’ ltrs within a 24hr period of septic effluent. Top
How do I off load this unit?
Offloading may be in one of two ways. The smaller spherical units have lifting shackles or straps on opposite sides of the turret to facilitate lifting. Larger horizontal tanks should be under-slung using equally spaced straps. Alternatively the tanks may be lifted using a forklift if within a merchants yard.
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Does the septic tank need chemicals?
No, these tanks work better without added chemicals. Top
How is the unit installed?
These units should be placed on a concrete slab within an excavation. The tank should be ballasted to a level not greater than 300mm above level of the backfill material.
Concrete is the recommended backfill material.
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What type of pipe work is needed for my land drainage?
Two generally accepted types, both are uPVC underground pipe in either slotted or drilled (perforated).
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What is a good rate of fall from my property to my septic tank?
Based on 110mm dia (4”) it is generally acceptable to use 1:40 to 1:60 gradients as detailed within section H2 of the Building Regulations.
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How is the tank vented?
These tanks are generally vented via the inlet pipe-work, back to the soil stack pipe of the property. If the distance to the property is greater than 15m, a local vent should be considered. Top
How far does my tank need to be away from hard standing ground for the desludging procedure to take place?
WMost tanker operators carry sufficient pipe to facilitate sewage removal to a distance of 30m. Most tankers can actually draw up to 75m with sufficient hose and subject to the gradients of the site.
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Can I install this tank in trafficked area?
Yes, subject to the appropriate backfill and a concrete slab over the tank area, supported from the undisturbed ground surrounding the tank. This would need to be designed by a structural engineer and in all cases, the pedestrian duty access cover would be unsuitable. Top
Do you supply shallow septic tanks?
Some of the smaller size Septic tanks are available as horizontal units as opposed to spherical and as such are shallower. Top
Can I use perforated coil land drain for my soak away?
These convoluted hose types are not generally recommended, they have a tendency to silt up due to the ridges within the pipe structure. Whilst very effective as a means to draw ground water from the ground, this type may have a short service life as a soak away system. Top
Can I install my soak away under the drive or paved area?
No, access roads, driveways or paved areas should be located within the disposal area. Top
What is a percolation test and who carries it out?
A percolation or Porosity test should be completed to establish the soil characteristics and these results then used within a basic calculation.
A = Vp x P x 0.2. where A = the plan area of the soakaway system, Vp = the seconds per millimeter (results from the percolation test) and P = population using the system.
The result of this calculation will provide an area in m². This will then be converted into the length of the slotted/perforated pipe-work within a soakaway system.
These tests re generally completed by the installer.
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How often should I empty my septic tank?
It is good practice to empty septic tanks on an annual cycle. Top
Who can I get to empty my septic tank?
There are many registered tankering or wet waste companies, whilst a number are used by Kingspan Environmental Service the best place for an private end user to source a company is to check the yellow pages and get 2 or more prices quoted. Always ensure the volume of the tank is known and never request an ‘urgent’ empty unless necessary as the cost is generally greater. Currently VAT I not applied to domestic tank emptying.
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