French farmhouse renovation - May 2019

Nick Inman charts the ups and downs of doing it himself in our regular column... here, he talks candidly about sanitary issues and the dirty secret of a septic tank owner

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When we were considering buying this old French farm, the last thing I thought to ask about was what happens when I flush the toilet.

In rural France, when you become a property-owner you often also become the manager of a private sewage treatment plant, normally called a septic tank (fosse septique).

This is hidden underground and inconspicuous. You are not supposed to notice it and until you take a look you don’t realise what a low-tech marvel you have.

If you are about to renovate a house that does not already have a drainage system, you will have to devote a fair bit of time and money to the task.

Before you get the contractors in, you will need a geologist’s survey to determine the best location for the tank and the pipes, according to the soil type and the level of the water table.

Then you are required to apply for permission from the official organisation that makes sure no one’s septic arrangements become a public health hazard – the delightfully dominatrix-sounding Spanc.

One expert told me that even if a septic system is a big outlay, the investment is earned back in six or seven years compared with the higher water bills that come with the luxury of mains sewerage.

Not that you have a choice.

There are various forms of financial aid available for installing or improving a private septic tank, including grants and interest-free loans.

All of them come with qualifying conditions. To find out what help you are eligible for, ask at your town hall or see the website of the Agence National pour l”Amélioration de l’Habitat, at

Like many house-buyers, we inherited our septic system without much thought to its efficiency – but we had to have Spanc approval to continue to use it. In any case, it is worth knowing how things work before a blockage causes a back up that requires the expensive intervention of a plumber.

It took some time to figure out the components but there are diagrams online, with all necessary French vocabulary.

Whatever the configuration on a property, the basic concept is always the same: a septic tank breaks down as much waste matter as possible and produces cleanish water that flows through a filter and drains into the soil via a network of parallel pierced pipes.

The only thing you have to do is get a specialist to pump out the solid stuff once every few years and take it away.

I have learned from experience to treat my septic tank with the care and respect it deserves. It contains a living eco-system of excrement-eating bacteria and – if I keep an eye on it – will function for years without problems, free of smells and overflows.

Owning a septic tank makes you circumspect about what you flush away: anything that doesn’t readily decompose and any chemical that kills bacteria are definite no-nos.

Sewage processing may not be something we want to talk about but it is a serious environmental issue. A lot of drin­kable water runs into septic tanks and municipal sewage systems – a sign of how wasteful and spoiled we have become.

In an ideal eco-world we wouldn’t have sewage works or septic tanks: we would use composting toilets and straw bale urinals to process waste naturally. Our “grey” water would be purified in reed beds before being used to water the garden.

For now, all I can do is learn to love my septic tank and be in awe of its silent operation.