Septic Tank Servicing & Maintenance

It is recommended to de-sludge a septic tank at least once a year but this varies with the system’s capacity and use. You must de-sludge the septic tank if scum is present in the second chamber or if the sludge comes up to about 400mm from the bottom of the tank. A minimum of 75mm of sludge should remain in the tank to assist in the re-seeding of the new sludge. Regular maintenance is required to ensure that the septic tank operates effectively and that solids do not enter the percolation area and clog the distribution pipe work.

Yes. All on-site wastewater treatment systems require ongoing maintenance to ensure that the system is providing adequate treatment of the wastewater. An on-going maintenance agreement should be made and renewed with an appropriately qualified person to ensure that your wastewater treatment system is working effectively at all times.

Oils and grease from cooking that escape down the drain can damage your system. Food waste and cooking oils can be recycled (see information below) and avoid the use of food macerators or “in-sink disposal units” Excess amount of food, grease or oils will cause blockages, smells, overload your treatment system and damage you percolation area.

Grease traps capture the oil and grease from the flow of wastewater by slowing down the flow of hot greasy water through the trap and allowing it to cool. As it cools, the grease and oil separate out of the water and float to the top of the trap. The cooler water then flows to the septic tank where it is treated. Grease traps are usually not included in the design of a domestic wastewater system but are mandatory in systems treating water from restaurants, hotels and any other businesses that supply food.

Due to the absence of these systems in single dwellings, it is highly important that people do not allow any fats, grease or oils to enter their septic tank systems. The inlet pipes can become clogged up with the fats and grease and therefore can reduce the treatment rate of the septic tank system. To ensure that this doesn’t happen to your system, all fats, grease and oils must not be disposed of down the sink or drains.

Grease traps capture the oil and grease from the flow of wastewater by slowing down the flow of hot greasy water through the trap and allowing it to cool. As it cools, the grease and oil separate out of the water and float to the top of the trap. The cooler water then flows to the septic tank where it is treated. Grease traps are usually not included in the design of a domestic wastewater system but are mandatory in systems treating water from restaurants, hotels and any other businesses that supply food.

Normal amounts of household bleach, disinfectants and detergents will not harm the domestic wastewater treatment system. However, excessive amounts of bleach will temporarily reduce the treatment capacity, as the microorganisms needed to treat the biological waste will be killed off. In saying this, the system should return to full performance capacity within a short period of time. It is important to be aware of potential effects that excessive use of these chemicals will have on your wastewater treatment system.

The frequency of de-sludging is dependent on the size of the tank and the number of persons living in the house.

Best practice for the management of DWWTS indicates that de-sludging should be undertaken when the level of sludge on the bottom of the tank is greater than approximately 400 mm. A minimum of 75mm of sludge should remain in the tank to assist in the re-seeding of the new sludge. Regular maintenance is required to ensure that the septic tank operates effectively and that solids do not enter the percolation area and clog the distribution pipe work.

In Ireland, there are approximately 440,000 houses with domestic waste water treatment systems and on the basis of US figures the annual septage volume can be estimated at 0.372 x 109 litres /year or 372,000 m3/year.

It is recommended that a waste contractor that has an appropriate waste collection permit be employed to de-sludge a septic tank or DWWTS. A list of approved permit holders is available from the Environment Section of your Local Authority.

Householders having their septic tanks de-sludged should ensure that they retain a receipt from the permitted waste undertaker who de-sludges the tank.

The receipt should include the following information:

 Name, address and Permit Number of the waste collector.
 Date of desludging.
 Quantity removed and destination to where the sludge is to be taken for treatment and disposal/recovery.

Individual landowners can dispose of sludges from their own DWWT system by land spreading, strictly in accordance with the requirements of the Waste Management (Use of Sewage Sludge in Agriculture) Regulation, S.I. No. 148/1998, as amended.

Permitted waste collectors can also dispose of sludge’s by landspreading where their Waste Collection Permit allows them to do so strictly in accordance with the requirements of the Waste Management (Use of Sewage Sludge in Agriculture) Regulation, S.I. No. 148/1998, as amended.

The Permitted Waste collector must ensure that sludges are treated and disposed/recovered in accordance with legislative requirements.