Problem in getting the lid off of the fosse septique!

[nectarine]

We've had our house for two years and don't know when the fosse was emptied, but know where it is ... a concrete square that has four bolts on each corner. SAUR came to inspect the fosse, said it's fine but couldn't get the lid off to look inside, but he said it should be emptied every 5 years or so ... so I guess it is due as the previous owners told us they'd never emptied it.

Problem is ... the bolts are solid! We've tried oil, WD40, everything, torque wrenches and various tools that Mr. Nectarine hoards in his workshop ... nothing. Various strong-armed male relatives have come and had a go ... nothing.

I;m guessing the fosse is several years old ... 20 years or more?

Speaking to the fosse-emptying company, they said they would not lift the lid, it had to be ready open for them (guess in case they break something).

But my question is ... if we drilled or broke open the lid, how easy would it be to get another lid from a fosse company that would match the hole and existing fittings? You wouldn't want it open for long without a lid!

Or any advice on how to get it open.

We're stumped for an answer!

Many thanks

[Pierre ZFP]

Have you tried applying heat?  A good long blast with a blowtorch might do the trick

[pachapapa]

Try Mr nectarine's impact wrench.

[La Guerriere]

If the bolt heads stick up you might be able to get 'em off with an angle grinder.

[Théière]

Or excavate round the lid and use a nut splitter if they are not encapsulated. Not much point in applying heat to the head of a bolt but to the nut would be good.

Make sure you replace them with stainless steel and a bit of grease.