Installing or replacing a septic tank

Note that septic tanks are still available in France, but it is now quite common to use a micro-station - something like a septic tank is still used, but instead of a sand filtration bed, air is pumped through the microstation which causes the contents to be broken down more quickly. Less garden space is needed, there is less possible future trouble because there is no filtration bed to get blocked, but the electric pump operates a lot of the time so has a running cost.

Owners of houses that are not on mains waste disposal can (and should) get advice from the local water authority about which system is suitable for their property, land size and type of terrain. The best answer to the problem is not always the one you think it will be and rules nd regulations change quite frequently, typiclly getting more strict when they change.

As someone who has paid for two at the same property and two others at other properties, I can confirm they are expensive (typically 7 000 - 9 000 euros) and existing systems at a property very often fail to comply with current legislation so I recommend you budget for this in your initial cost calculations, then be pleased if it is unnecessary.

During the last few years the rules about septic tanks in France have been changing alarmingly frequently, and it has been the responsibility of the property owner to ensure compliance. This compliance is to ensure that environmental standards are met.

All very interesting, but what does that mean for you the householder. It means that if you do not have a septic tank system that meets current standards and regulations, and most old properties do not, you will almost certainly need to get one sooner or later. If you don't, when you come to sell the property one of the standard checks will show that there is a problem.

Equally importantly, if you are getting a new septic tank system anyway, you should get one that complies with the regulations.

The first stage will be to get a soil test performed on your property. Your mairie will be able to give you the name of the local agency that performs the tests, and it will cost you a few hundred euros. A septic tank should cannot be installed without this test being carried out first, since the test will enable the authorities to tell you what size and type of system you need in order to comply.

Previously the most common type of septic tank comprised a large tank, buried in the ground, that collected all toilet waste from the property, and then released it through a series of underground pipes into the surrounding area. Typically 20 - 50 metres of buried pipe were installed.

It depends on how absorbent your soil type is, but you should be aware that this is now almost certainly not a compliant system. The most common system now involves a very large hole being dug, perhaps 30 square metres and 1.5 metres deep, lined with heavy duty plastic, then filled with various layers of sand, gravel, and geotextile membranes.


The outflow from the septic tank (which has received ALL waste water from the house, not just toilet waste) then passes into this filtration system, through pipes spread across the top, filters through the sand bed, and is collected by further pipes at the bottom before being released into the environment.

If your property is on very sandy, absorbent soil you might be permitted to have a more simple trench based system; if it is built on rock there are separate specifications again.

Further rules specify, for example, that the filtration bed must be more than 35 metres from a natural water source (spring or well), and that rainwater from nearby roofs etc must not pass into the filtration bed.

This filtration bed costs a lot more than the septic tank itself - 5,000 euros is common for the complete system. Not surprisingly, digging a swimming pool sized hole in your garden involves heavy machinery. This is messy and disruptive, so should usually be planned for as early in the work program as possible.

The last important aspect of the fitting is a ventilation pipe leading out of the septic tank. Usually this will go up the side of the property to roof level, to keep odours away.

Ongoing use of your septic tank

Usually a new septic tank will need no maintenance, although it should be emptied at least every four years.

Care should be taken that bleach based products are not flushed down toilets or sinks. If these are used too enthusiastically the bacteria in the septic tank will be killed and the tank will cease to function.

A product available in supermarkets called eparcyl will 'kick-start' a septic tank. We never need one in our own property, but in a rental property we use it before the season commences (likewise for a holiday house with infrequent use).

We have been told that a dead rabbit thrown in a septic tank will also bring it (the septic tank, not the rabbit) back to life, but I've never tried it!

Other products are available for dealing with temporary odour problems. Ongoing odour problems should not arise with a new correctly fitted system.