Knollands Septic Tanks & Drainage

Desludging a septic tank

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Klargester recommends emptying the septic tank at least once a year. This assumes that you have the correct size of tank installed in relation to your water use and household size. The table below provides guidance as to the most appropriate tank selection for your domestic household, but for advice on other situations such as office developments please contact us.

The decision on how frequently to empty the tank is yours to take, considering your addition of solids, bacterial compound and household size. Where you have extended the emptying frequency, you should regularly check the condition of the effluent passed to the soakaway in the inspection chamber for the absence of visible solids.

Do not over extend the desludge period as this may allow sludge to accumulate to such an extent that damage can result within the septic tank. It may be difficult for the waste disposal contractors to empty tanks with very high solid contents. Always check the appearance of the septic tank effluent and never allow the septic tank to become blocked.

If the sludge is allowed to accumulate in the tank for too long, there will be a smell. More importantly, excess sludge in the tank allows excess release of solids into the soakaway drains which may become blocked. Once the soil around the drains has blocked, it is very expensive to repair or replace. We do not recommend extending the desludge frequency at the expense of your irrigation system.

You may know of neighbours who say that they have never emptied their septic tank. This may be because they have an old tank which was built of brick, or perhaps a pit with a very large capacity. As these systems age, they tend to leak both liquids and solids through the old cement joints rather than through the designated irrigation drains. The result is often contaminated areas and ponding local to the tank.

Desludging Instructions

Always employ a licensed waste disposal contractor who holds the relevant permits to carry and dispose of wastes. You should be provided with a disposal note.

We suggest the use of a maximum suction hose diameter of 4" or 110 mm.

a) Spherical septic tanks with submerged floating balls

Lower the tank hose down through the access shaft close to the wall of the neck and draw off sufficient effluent to cause the ball to drop away from its seating giving access to the main sludge holding chamber.

Remove sludge from the main chamber. Care should be taken to avoid unnecessary striking of the ball seating by the suction hose. When the tank refills, the ball will automatically re-locate in its seating to seal off the main sludge holding chamber.

b) Spherical septic tanks with raised necks

Lower the tank hose down through the centre access shaft and remove the sludge from the main chamber. Care should be taken to avoid unnecessary striking of centre baffles by the suction hose.

c) Spherical septic tanks with plug and handle

Lift out the plug using the handle. Lower the tank hose down through the centre access shaft and remove the sludge from the main chamber. Care should be taken to avoid unnecessary striking of centre baffles by the suction hose. Replace the handle and allow the tank to refill.

Non Domestic Sewage

Sewage from a commercial source, i.e. catering establishments, pubs and restaurants usually requires the installation of a suitably sized separate grease trap which is installed on a separate drain from toilet and other wastes. Other issues should also be considered, please contact us for guidance.

Large Cylindrical Septic Tanks

These tanks are generally supplied for multiple housing systems or for commercial applications. Please contact us should you have any queries about their operation or application.

Septic tank factsheets:

Septic Tanks

Our range of septic tanks are suitable for both domestic and commercial applications and for populations of 1 up to 500 people. The Knollands Bio-Pure septic tank is an innovative and cost effective solution and as a result is our best selling septic tank.

Drainage systems

Wether it be agricultural drainage coil, twin walled CorriPipe™ or Hunter sewer drains, Knollands can offer quality drainage systems for a number of different requirements and are perfect for use with our range of septic tanks and rain harvesting products.

rain harvesting

Knollands supply mainly Graf Carat S underground tanks due to their quality construction and reliable design. Convenient packages that include everything you need to start rain harvesting result in a simple and enjoyable project that benefits you and the environment.

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