No permission to use shared septic tank -WWYD?

[Heje]

We're buying a property and nearing exchange. The sellers are putting a lot of pressure on us to exchange ASAP due to their onwards purchase.

The property shares a septic tank with its neighbour. It was part of a larger plot including a barn but about 20 years ago the barn was sold separately. Both properties use a septic tank in the garden of the barn conversion.

Conveyancing has revealed that at the time the properties were legally divided they forgot to grant rights for use of the septic tank to the property we're looking to purchase. It's been used by both properties without issue with shared cost all this time.

I know it's not likely but it seems legally possible that whoever the neighbours are could prevent us using the septic tank.

Ideally we'd want the sellers to agree to arrange for the neighbours to explicitly grant the right, but I think they won't want to delay. My solicitor mentioned an indemnity but even if it was watertight it wouldn't prevent a whole load of potential hassle.

Has anyone come across this before? WWYD if the seller refuses to try and legalise the permission?

That’s good news OP.

Once the Deed is created and agreed, the Land Registry Will apparently expedite matters where a sale is involved.

The Deed shouldn’t need to take long?

It's probably gained rights by prescription that they can register at land registry but yes make them sort it via their solicitor before completion it could be a real headache and you risk septic tank owner holding you over a barrel for £££