1000 litre IBC for under ground heating fuel?

Are you going to bury it, or put it in an underground room?

There's a potential of it collapsing when empty due to the weight of the surrounding ground.

Also I think all fuel tanks must be bunded to meet regulations, but don't quote me on that

I have oil fired heating but i have a double skinned plastic tank above ground

www.oftec.org.uk/consumers/domestic-oil-tanks-and-storage

If it splits, there could be an oil leak of up to 1000ltrs.

This could contaminate tonnes and tonnes of soil. The clean up costs alone would be in the thousands, if not tens of thousands...

Personally I'd go for a bunded tank.

IBCs are actually manufactured for dangerous goods. A lot don’t realise it’s a generic term applied to a wide range of pack types, not just the typical composite metal frame / plastic bund type.

For that IBC type the service life is five years. Commercially available plastic heating oil tanks typically only have a two year guarantee (!).

By virtue of your installation method you would achieve a bund capable of holding more than the IBC’s capacity and it would have the advantage of not being exposed to UV. If you could line the pit with tanking impervious to oil all the better.

It’ll be easy to fill, just need a lift pump.

Suggestion: see if you can find an IBC with a metal bund instead of a plastic one (they do exist)?