"Sacha" wrote in message
"Charlie Pridham" wrote:

Most people I know with modern ones have a yearly contract.

I think there might be quite a lot in that last sentence, Charlie. I'm a
bit concerned that the OP is hearing about people who haven't touched a
tank
in 15 years if his house's previous owners are on a yearly contract! I
wonder if a specialist surveyor exists for such things?

But many of the posters have made the distinction that it depends on the
type of tank he has.

I know that here in Australia, if you have one of the modern ones which will
pump out onto the garden, the contract is for attention every 3 months. Not
for pumping out but for checks on the water quality.