Maintaining Your System

Your new waste water treatment system has been an expensive investment, so you want to make sure that it is looked after and lasts as long as possible!

Or maybe you are searching for advice on how to maintain your existing system so that it continues to function efficiently.

There are many systems now available in France, so the Manufacturer’s handbook should be individually referred to for specifics relative to your installation. Your installer will provide this for you, or if you installed the system yourself, then it will be available from the Manufacturer or Supplier directly.

The following are general guidelines appropriate for all systems:

  • Do not use weedkiller near the system – pull up any weeds by hand if necessary.
  • Limit the use of products that will affect the treatment of the waste water. Remember that the process of treating waste water is biological and therefore vulnerable to chemical in-balance.
  • Maintain the system, so that it continues to function well.
  • Waste water and solid waste within the system can contain bacteria and pathogenic viruses. Therefore when maintaining the system: Wear protective gloves and eye protection and wash you hands well afterwards. Alternatively, please do not hesitate to contact a profesional to maintain the system for you.
  • Verify that the lids are well screwed down. They need to remain accessible and free of weeds. Do not drive directly over the lids.


The following products should not be put into any system, whether Traditional Fosse and Filter Bed, Microstation, Compact Filter or Reed Bed – they can affect the biological process necessary to break down the waste in the water and treat it:

  • Paint, varnish and solvents, such as white spirit etc.
  • Petroleum products
  • All toxic products – check the label
  • Anything that does not biodegrade easily, such as cigarette butts, feminine hygiene products, condoms, ash, product wrapping, cleaning wipes etc
  • Water from a swimming pool.

It is advisable to also limit the use of products such as bleach and non-biodegradable cleaning agents. These can temporarily affect the bacteria levels in the system. Instead use cleaning products recommended for ‘Fosse Septiques’ and biodegradable washing powder.

Cooking oil, such as when you empty a chip fryer, should never be put into the system. Your system can cope with a small amount of oil or cooking fat, but try and limit the amount that is washed down the sink.

Fats can congeal in the pipework, so if the system is further than 10m from the kitchen you probably have a grease-trap installed to catch and retain all fats. This will need emptying out periodically, so it is worth checking it every 6 months.

If you do not have a grease trap, then rodding points will enable you to keep the system flowing.


Your system will need periodic checks to make sure it is operating correctly. Some systems require a Service Contract in order to make sure they conform (particularly Microstations). Check with the installer or Manufacturer as to whether you need to have this. Depending on the system installed, then this Service Check will be either every year or every two years.

It is advisable to check the level of solid waste in the system – depending on how many people are using the system, then you can check the level every 6 months to each year for low usuage. Once the solid waste in the system reaches over 50% then you need to contact a registered company called a ‘Vidanger’ to empty the system. Ask for recommendations from neighbours or Pages Jaunes ( is a good place to find local companies and you can then compare prices before choosing your vidanger.

They will need to know:

  • The size of your system either in litres or cubic meters
  • Access to the system, i.e. the distance in linear meters from the system to their nearest access point. They can then provide the correct length of hose for emptying the system.


Unless your system has been installed specifically so that it can be driven over, you need to make sure that no one drives over it! The last thing you want is damage from a vehicle. If the system is near a road, driveway or access point, you might want to consider creating a flower bed around it or fencing it in with a low border.