Old, unused septic tank

[Hoolahoophop]

We have recently bought a house. It is on mains sewerage, this was an issue that came up in the searches and was confirmed. Since moving in we were curious about a random concrete slab in the lawn. Looking under it we found a hole, constructed of bricks which we assume is an old, now unused septic tank. No smells from it. Is this something we need to get rid of? Or can we leave it with the slab on top and forget about it.

Any ideas how much it would cost to remove if we need to remove it?

Thanks

You don't have to do anything with it as it's now not in use. You can just leave it.
It could be utilised for rainwater storage though if you've the money to get it installed.

We are installing a water treatment plant (new type of septic tank) and the old septic tank is some distance away. The builder has used it for disposing of rubble so it's saved the cost of a few skips!

Thanks for your replies. That is a relief, I googled it and lots of tank removal companies said it must be taken away at a cost of several thousand pounds as it will be a health hazard!

We shall ignore for now and only think about it if we want to do anything with that part of the garden.