FAQ’S About Waste Water

Here you’ll find the most complete answers to any of your waste water related questions!

What is included in the term domestic wastewater?

Domestic wastewater includes grey water and sewage from domestic dwellings.  Grey water is defined as wastewater that comes from sinks and washing machines, i.e. the wastewater that contains some bleach and detergents.  The grey water from your household is treated in the same way as sewage whereby it is collected in a septic tank and undergoes treatment either in a percolation area or in a secondary treatment unit prior to being discharged via a polishing filter to ground. Rainwater is not classified as grey water and therefore should not be discharged into your wastewater treatment unit.

What happens to wastewater from my home?

When houses are not served by a public sewerage system, the wastewater from a house should be treated by a septic tank and percolation area or advanced wastewater treatment system. With new houses the type of system used is determined by testing ground/soil conditions at planning stage.

How should a septic tank wastewater treatment system work?

A modern septic tank system includes a double chamber tank and percolation area. Wastewater is partially digested by bacteria in the septic tank and the effluent then passes through a percolation area where effluent is further treated. Read More

Should ‘grey water’ from dishwashers, sinks and washing machines be directed to my wastewater treatment system?

YES – grey water should in all circumstances be directed to the wastewater treatment system. Grey water is also a pollutant and if directed to the rain water system may cause contamination of waters. Take care with house extensions or alterations – don’t connect any wastewater pipes to the rain water disposal system.

Should water from roofs and yards be connected to my wastewater treatment system?

NO – Roof and yard waters should not be connected to your wastewater treatment system. Clean water should be collected and discharged separately to a local watercourse or soakaway.

How do I dispose of the rainwater and clean surface runoff from my site?

Uncontaminated water should be disposed of by means of a soak pit/soakaway.  The soakaway should be designed in accordance with the guidance provided in BS8301 and in BRE Soakaway Design (1991). It should not be located within 5m of any dwelling and as far away as possible from the percolation area (at least a minimum of 5m separation distances should be used).

How do I know if my wastewater treatment system is not working properly?

Some signs that your wastewater treatment system may not be working include the following:

  • Smell of sewage from the general area of the tank and percolation area.
  • Slow draining toilets, sinks or drains or backing up of sewage at the inlet.
  • Overflow of wastewater from the tank or ponding of sewage on the percolation area.
  • Discoloration of nearby watercourses (greyish slime growths).

My house is over 20 years old – how do I know if it is working effectively?

Septic tanks prior to the 1990’s may not be built to current standards and performance should be checked. You should check tank structure, provide access points for maintenance and de-sludging, replace soak-pits and pipes to drains (if present) with a properly designed percolation area or other approved polishing system, exclude roof and yard water from the system.

I have noticed ponding in my garden close to my wastewater treatment system, what should I do?

First of all you should arrange to have your system de-sludged. If it is an advanced wastewater treatment system you should contact the supplier/installer of your system and have your system serviced.

Could my wastewater treatment system pollute my well?

Yes it is possible. If you suspect that your wastewater treatment system is affecting your well you should have it checked.  If you are concerned you should contact your local authority’s Environmental Section or local Environmental Health Officer for advice.  If you suspect contamination of your well you need to have a full assessment of your wastewater treatment system carried out by a suitably qualified person.

When buying a house what do I need to do?

Before buying a house you should have the septic tank or wastewater treatment system inspected by a suitability qualified person. You should ask for installation and maintenance records for the system. You should check that the treatment system will adequately serve the anticipated number of occupants of the house.

If the house is served by a DWWTS, the seller of the house should provide you with a copy of the certificate of registration for the domestic waste water treatment system as provided for in Section 70 D of the Water Services (Amendment) Act 2012.

The new homeowner is obliged to inform the local authority of the change of ownership and such that the register can be updated.

I want to extend – can I build over my septic tank system and percolation area?

Under no circumstances should you build over a septic tank or percolation area. Access to the tank is needed for regular maintenance and the percolation area should not be compacted.

Even with a hard standing area located above a percolation area traffic may damage percolation pipes and result in ponding or escape of untreated effluent.

Can I place a car park or driveway over the percolation area or polishing filter?

Roads, driveways or paved areas or any underground services must not be located within the disposal area.  This is due to the need to have easy access to the site for maintenance and also to prevent problems with the system due to the potential for damage to the pipework and compaction of the filter materials.

Are all sites suitable for septic tanks and other individual wastewater treatment systems?

NO– not all sites are suitable. The following are possible reasons for site unsuitability:

  • A high water table.
  • A slow percolation rate of the soil which would result in ponding on the surface because effluent cannot get away
  • A fast percolation rate of the soil, which would result in effluent moving through the soil too quickly without effective treatment.
  • Site restriction issues i.e., not enough space to achieve the minimum separation distances between the treatment system and domestic wells, watercourses, other houses etc.

The site suitability assessment process will determine the suitability of a site but the ultimate decision will rest with the local authority or planning authority.

Why do I need to de-sludge my domestic wastewater treatment system?

If the level of sludge builds up in the tank it may make its way out of the tank and block the distribution box and the percolation area or polishing filter. And if the percolation area or polishing filter becomes blocked it is very difficult to clean and may require replacement – an expensive option!

The minister has published new regulations governing the operation and maintenance for domestic wastewater treatment systems (DWWTSs).  These require owners of DWWTS to operate and maintain their systems and this includes de-sludging.

How do I care for my domestic wastewater treatment system?

You should visually check your system at least every six months and note any ponding of effluent, bad smells or discoloration of nearby drains. If you have an advanced treatment system check the electrical components (pump, blower etc) are operational.

Don’t be tempted to turn off the power to save electricity – If there is no air going to the system it becomes an undersized septic tank and treatment is ineffective. You should also check the distribution box i.e. the manhole between the wastewater treatment system and the percolation area to ensure even distribution of effluent and ensure there are no blockages.

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