Martin Burke from Burke Waste Water Systems, Co Galway, and Frank Gallagher, a licensed collection contractor from Sligo, share their advice about the steps you should take to assess the performance of your system, how to carry out simple repairs if needed and what’s involved in upgrading to a new system.

Desludging

Septic tanks should be emptied at least every year, whether they are new or old. The main reason for this is to remove material that is slow at breaking down. Neglecting to empty a septic tank can accelerate the failure of the tank’s percolation area.

During a septic tank inspection, you may be asked if your system was desludged and the inspector may look for a certificate of compliance – proof of regular desludging with a licensed contractor. It is the legal requirement for a householder to use the services of a permitted contractor.

Desludging of a septic tank usually costs between €140 and €180, depending on distance to the treatment plant and emptying charges. A farmer who empties his/her own septic tank with his/her own farm tanker and spreads the material on his/her own land in accordance with a nutrient management plan and once grassland is not grazed within six months does not require a permit.

Identify if you have a problem

A poorly functioning septic tank may be characterised by problems flushing toilets, backing up of sewers around your house, bad odour and flooding or ponding of sewage around the percolation area. These are the tell-tale signs of an issue with your on-site sewage treatment system.

Sometimes tanks can also be physically damaged with cracks visible. If there is visible damage to the tank or if the tank is single-chambered or too small, the tank needs replacement.

With an advanced sewage treatment plant, you may know the system is not working properly because of an alarm or because an air pump has stopped working.

Possible repairs

In some cases, a system can be repaired with minimum work needed. A properly fitted T-bend in the inlet is essential. This is because as waste water arrives in the tank, the rate of movement is slowed by the T-bend and solids settle to the base of the first section. Grease and other light solids rise to the top, developing a scum. The sludge and scum are held while the treated waste water is discharged to the percolation area for final disposal to ground.

If the T-bend is fitted too high or if there is no T-bend at all, the splash effect from the solids entering a tank may limit the formation of this scum and anaerobic breakdown of waste cannot work properly.

Baby wipes should not be let into the tank, as they cannot break down, which may cause serious blockages in tanks with moving parts. In advanced systems, they can wrap around pumps and cause the pumps to burn out.

Regarding the percolation area, during the building boom years, many one-off housing developments put in sewage outlets from their houses that were too deep. This meant the percolation area had to be laid too deep. The soil at lower depths in many cases does not have good soakage, so many of these systems are now giving trouble. The advice would be to lay the percolation pipes at a depth of one foot.

What size of tank?

As a rule of thumb, to calculate the size of the tank required, multiply the number of people in the house by 150 litres (as a person uses 150 litres/day) and add 2,000 litres. For example, a six-person house is (6 x 150) + 2,000 = 2,900 litres. So, for a household with six people, a tank capacity of 2,900 litres is required.

Costs

Cost of installing a septic tank/treatment unit varies for each household. The costs vary depending on a number of factors:

  • Whether the site is low-lying or marshy.
  • Presence of bedrock.
  • Type of percolation bed.
  • Type of treatment unit.

    • The overall cost ranges from €5,000 to €7,000 plus VAT.