On the grey water front

Drains may be out of sight and out of mind, but ig­nore them at your peril! Ian Mor­ris pro­vides a be­gin­ner’s guide to French drainage sys­tems

French Property News - - Contents -

We go down the drains to in­ves­ti­gate the murky world of waste water dis­posal

Most peo­ple seem to think that if you can flush the WC and not be trou­bled by what hap­pens next, the drains must be okay. But this ar­ti­cle could be use­ful if you’re about to buy a house in France – par­tic­u­larly an old prop­erty – or if you are trou­bled by drainage prob­lems in the fu­ture.

The ba­sic de­sign of a drain is a se­ries of pipes, prop­erly con­nected so as to be wa­ter­tight, laid in a straight line and at a uni­form gra­di­ent. The gra­di­ent is im­por­tant other­wise noth­ing goes any­where. And, de­pend­ing on lo­ca­tion, it might be im­por­tant to make sure the drain is pro­tected from be­ing crushed – by the weight of ve­hi­cles, for ex­am­ple, if it runs un­der a road.

It would be nor­mal prac­tice, at least in the UK, for in­spec­tion cham­bers to be pro­vided at in­ter­vals along a long run of drain, and par­tic­u­larly at those points where the drain changes di­rec­tion. The in­spec­tion cham­bers, or man­holes if you like, are to pro­vide ac­cess for drain clean­ing rods to be in­serted to clear any block­ages that might un­for­tu­nately oc­cur. This could prove to be im­por­tant where the drains serve a gîte, or rented prop­erty, where guests or ten­ants don’t think twice about putting dis­pos­able nap­pies and other po­ten­tially dis­as­trous items down the drains, ir­re­spec­tive of what you might tell them.

Pipe dreams Sadly, in France, drains rarely live up to the stan­dard de­scribed above. Lengths of drain are fre­quently not straight, and are laid at ir­reg­u­lar gra­di­ents, en­cour­ag­ing block­ages to oc­cur. In­di­vid­ual lengths of drain are of­ten so long be­tween ac­cess points that it would not be pos­si­ble to clear block­ages be­cause drainage rods long enough sim­ply don’t ex­ist. And, worst of all, ac­cess points or in­spec­tion cham­bers are rarely pro­vided at changes of di­rec­tion, or at all.

I would es­ti­mate that in well over 75% of the prop­er­ties I have sur­veyed in France, the drains do not have any in­spec­tion points or in­spec­tion cham­bers at all. At best, there is usu­ally an in­spec­tion point where the drain from a prop­erty runs out across the bound­ary to join a pub­lic sewer. In­spec­tion points in in­stances such as this in­vari­ably con­sist of a 300mm di­am­e­ter plas­tic tube, some­times ex­tend­ing down more than two me­tres, such that you can see the drain but can­not phys­i­cally get to it. All in all, if the stone from your di­a­mond ring is ac­ci­den­tally dropped down the waste pipe while you’re wash­ing your hands, you can pretty much safely say you will never see it again.

In­spec­tion cham­bers – where they ex­ist – are of­ten poorly made, with no ‘in­vert’ (the chan­nel pipe that you would ex­pect to run across the bot­tom of the in­spec­tion cham­ber). The in­te­rior of the cham­ber is of­ten of very rough con­crete that you could be ex­cused for think­ing had been de­signed to en­cour­age block­ages. Some­times the in­spec­tion cham­ber is in the form of what I would de­scribe as a ‘catch­pit’ where the bot­tom of the cham­ber is lower than the in­let and out­let pipes such that it is al­ways full of sewage.

In re­cent years, drainage in­spec­tion cham­bers (where they ex­ist) have tended to take the form of pre­fab­ri­cated plas­tic units which at least al­low a free flow of waste water. It is rare for any of the fea­tures I have iden­ti­fied above to be men­tioned in any of the statu­tory re­ports that have to be pro­vided by a ven­dor prior to the sale of a prop­erty in France.

Why all the fosse? In my ex­pe­ri­ence the ma­jor­ity of English-speak­ing buy­ers are at­tracted to ru­ral prop­er­ties, most of which, by virtue of their lo­ca­tion, are not con­nected, and are un­likely ever to be con­nected, to a pub­lic sewer. Prop­er­ties of this kind have to be pro­vided with their own, or per­haps a shared, drainage dis­posal in­stal­la­tion. And here the term that springs to mind is a fosse sep­tique (sep­tic tank).

It might at this point be worth men­tion­ing the dif­fer­ence be­tween a sep­tic tank and a cesspit. A sep­tic tank is a se­ries of two, or three, in­ter­con­nected cham­bers with an in­let at one end and an out­let (at a slightly lower level) at the other end. Bac­te­ria live in the cham­bers and break down the sewage that passes through; each cham­ber is in the form of a weir and, thanks to the bac­te­ria, solid mat­ter even­tu­ally falls to the bot­tom in the form of sludge and the liq­uid el­e­ment runs out over the top of the weirs and even­tu­ally out of the sep­tic tank.

It is vi­tal for the bac­te­ria to be al­lowed to do their job and for this rea­son you should never put bleach or other chem­i­cals that could kill the bac­te­ria into drains that con­nect to a sep­tic tank. Sep­tic tanks do not nor­mally need to be emp­tied but the sludge that grad­u­ally ac­cu­mu­lates at the bot­tom should be pumped out

A sep­tic tank will prob­a­bly need to con­nect into an ar­range­ment of per­fo­rated pipe drains like this, known as ‘épandage’

Sadly, drainage in­spec­tion cham­bers around older houses in France, where they ex­ist, of­ten look like this

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