Do I need to remove a disused septic tank in France after connecting to the mains?
Safety is the number one priority, says Sarah Bright-Thomas of Bright Avocats
A mains connection means septic tanks are no longer needed
Gozzoli / Shutterstock
Reader question: Do we have to decommission our old septic tank when we connect to the mains? Will the Spanc actually check this?
For your own safety, if for no other reason, you do have to do some work on your old septic tank after your house is connected to the mains.
Having mains sewerage arrive in a village is a big thing, so I am sure you will get lots of advice on how and when to do the connection and what happens afterwards.
It is not clear if the Spanc (Service public d'assainissement non collectif) will actually come and check – officially their role stops when your system becomes collectif.
Read more: What is the ‘soil survey’ required before fitting a septic tank in France?
Is leaving an old septic tank in place dangerous?
Leaving your old tank in place is risky.
The liquid inside is a biohazard, and over time the covers to the tank will crack or warp and there is a risk someone might fall in.
Children, in particular, can take great delight in jumping up and down on covers or tanks – there are occasional reports in local papers of them dropping in, sometimes with fatal results.
The basic decommissioning process is to arrange for the tank to be emptied, and then for you, or a specialist, to spray the inside with industrial disinfectant to kill the bacteria.
Then fill the tank with sand or soil so that if anyone does jump on a lid they will not fall far.
Infilling also means that the tank will not suddenly implode, either because the walls, designed to be pushed against the side of a hole by the weight of the liquid, collapse, or because you forget where it is and someone drives a tractor, lawnmower or other vehicle over it.
Alternatively you can arrange for the tank to be taken out. The tank is emptied, inlet and exit pipes are cut, and a digger or tractor with hydraulic front forks will lift it out using the built-in handles or chains passed through the hatches.
I have heard of people repurposing old septic tanks for rainwater by cementing closed pipe holes. However, it is probably better all round to buy a purpose-built rainwater tank.
