How to operate and maintain a septic tank
You have important responsibilities to operate and maintain a septic tank correctly. Some of these are required by law.
If you install a new septic tank, it must meet the requirements for building a new house.
Summary of the rules for septic tanks
What can and cannot go into your septic tank
How often to empty (de-sludge) your septic tank
Who can empty (de-sludge) your septic tank
Summary of the rules for septic tanks
Your septic tank (or any other domestic waste water treatment system) must:
- Be registered with Protect Our Water
- Be correctly maintained
- Be emptied periodically
- Not be a risk to people's health or the environment
- Not release waste water other than as designed or intended
- Not allow roof water or surface water from a yard to go into the tank
You must follow these rules. They are required by law. If you do not follow these rules, you could be fined or face another penalty.
The laws and regulations for septic tanks and domestic waste water treatment are listed below.
If you have a major problem with your septic tank, do not try to fix it yourself. Hire a qualified professional.
How a septic tank works
Learn how a septic tank works in this video.
What can and cannot go into your septic tank
These must go in your septic tank
Toilet water (3Ps: Pee, Poo and Paper)
Only pee, poo and paper should go in the toilet. Do not put cotton buds, wipes, etc. in the toilet as they can block the system.
Grey water
"Grey water" is water from your bath, shower, kitchen sink, washing machine and dishwasher. These often contain chemicals, oil and other pollutants. These must go into the septic tank. They should not go into ordinary water drains.
These must not go in your septic tank
Roof and yard water
Do not send roof or yard water into your septic tank system. They could overload it. This water should be collected separately and sent to its own soakaway.
Old or unused medicine
Do not flush old medicines down the toilet or sink. If you do, the medicines can end up the water supply. People and animals can then drink that water. This can cause us to become resistant to those drugs. This is already a serious problem and is increasing.
Visit MyWaste.ie for advice on how to get rid of old medicines.
For these things, it depends
Food waste, fats, oils and greases
Excessive amounts of food waste, fats, oils and greases can cause blockages, smells and affect your treatment system. Visit MyWaste.ie for advice on how to dispose of these items.
Bleach or disinfectants
Normal amounts of household bleach, disinfectants and detergents will not harm a septic tank system. Excessive amounts may temporarily reduce the treatment capacity. This is because microorganisms needed to treat the biological waste will be killed off.
However, the system should return to full performance capacity within a short period of time.
How often to empty (de-sludge) your septic tank
You need to empty your septic tank either every year or every few years. The rules below tell you how often to do it.
Emptying your tank is sometimes called 'de-sludging'. This is because it takes away sludge from the system.
Emptying a tank is an important responsibility. The law means that you must do it. If you do not, you could be fined or face another penalty.
Emptying your tank also helps to keep it working properly. If too much sludge builds up, it can affect how the tank works. It can also block the system. You might then need to repair it or replace it, which can be expensive.
The table below tells you how often you need to empty your septic tank.
The period of time depends on:
- The size of your tank. Tanks are measured in metres-cubed (m3). 1 metre-cubed (m3) = 1000 litres.
- The number of people in your home.
For example, you must empty your tank every 4 years if:
- Your tank is 3.5m3 in size, and
- 3 people live in your home
If you do not know how big your tank is, assume it is 2.5m3.
The law says that every time you empty your tank, you must keep proof that it happened. You must then keep this proof for the next 5 years. You can use the receipt from the company that emptied your tank as proof.
If you have a mechanical system, contact the manufacturer to find out how often you need to empty it.
How often to empty your septic tank
| Septic tank size | Number of people in your home | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Metres cubed (m3) | 2 people | 3 people | 4 people | 5 people | 6 people | 7 people | 8 people | ||
| 2.5m3 | 5 years | 3 years | 2 years | Each year | Each year | Each year | Each year | ||
| 3.0m3 | 5 years | 3 years | 2 years | 2 years | Each year | Each year | Each year | ||
| 3.5m3 | 5 years | 4 years | 3 years | 2 years | 2 years | Each year | Each year | ||
| 4.0m3 | 5 years | 5 years | 3 years | 3 years | 2 years | 2 years | Each year | ||
| 4.5m3 | 5 years | 5 years | 4 years | 3 years | 2 years | 2 years | 2 years | ||
| 5.0m3 | 5 years | 5 years | 5 years | 3 years | 3 years | 2 years | 2 years | ||
| 5.5m3 | 5 years | 5 years | 5 years | 4 years | 3 years | 2 years | 2 years | ||
| 6.0m3 | 5 years | 5 years | 5 years | 5 years | 3 years | 3 years | 2 years | ||
Who can empty (de-sludge) your septic tank
You must use an authorised collector to empty (de-sludge) your septic tank.
To find an authorised collector visit the NWCPO website (National Waste Collection Permit Office) www.nwcpo.ie.
Follow these steps:
- Click 'Quick Search'
- Then click the 'Select waste type' drop-down list and click ‘Septic Tank de-sludging'
- Select your county
- Click 'Search'
Farmers - emptying and using sludge from your septic tank
If you are a farmer, you can empty your own septic tank. However, you cannot empty a septic tank for anyone else.
In some circumstances you can spread the sludge from your own septic tank on to your land. Find out how to safely spread sludge from your septic tank.
To empty a septic tank and use the sludge on your land, you meet all legal rules and directions listed below.
Law and regulations for septic tanks
General law and regulations
Water Services (Amendment) Act 2007
Domestic Waste Water Treatment Systems Regulations 2012
Regulations for farmers emptying and using sludge from a septic tank
Waste Management (Use of Sewage Sludge in Agriculture) Regulations 1998
Waste Management (Use of Sewage Sludge in Agriculture) (Amendment) Regulations 2001
European Communities (Good Agricultural Practice for Protection of Waters) Regulations 2010