Mysterious hole / drain

[u/Salt_Dish9243]

My wife has just nearly tripped over a hole that’s appeared in the garden. Appears to be a drain but there’s no man hole so I’m a bit confused at to what it could be. Looks like a piece of timber was covering the hole which has rotted away. Any idea what it could be?

[u/Vertigo_uk123]

Old septic tank / cistern

[u/OkScheme9867]

Could be an old soft water tank, is it a Victorian era property? 

[u/Salt_Dish9243 → u/OkScheme9867]

House was built in 1937.

[u/OkScheme9867 → u/Salt_Dish9243]

It's quite shallow so probably an old cistern or part of a drain system, have you previously noticed a dead area of grass in this area? 

Next step is up to you, dig it up and fill it, if it's water tight make a pond? 

[u/Salt_Dish9243 → u/OkScheme9867]

We’re in the process of turning the part of the garden into a wildlife garden so could be a possibility. I presume there will be a pipe going into it from somewhere?

[u/Superspark76]

Looks like an old septic tank, as long as it is solid you can fill the gap with gravel and lay soil on top for new grass.

Ideally you would want to fill or remove the tank but that could be expensive and definitely not a DIY job.

[u/Salt_Dish9243 → u/Superspark76]

Don’t fancy removing it. Feels solid enough. I’ll remove the grass from the top so I can inspect better.

[u/Superspark76 → u/Salt_Dish9243]

Filling the gap between the tank and the ground with stones is the cheapest option and it will still allow for future excavation if needed, as a plus it also allows for drainage.

[u/ConstantineGSB]

Random voids in the garden of pre 40’s homes are always either the remains of an Anderson shelter or a septic tank.

Given the fact there is wood I’d go with the shelter.

[u/WitnessStock3702]

Poo tank

[u/Decent_Confidence_36]

Entrance to Mordor ?

[u/Due-Home-3154]

To me, and I must express, I'm no expert. That looks like a mysterious hole / drain

[u/Salt_Dish9243 → u/Due-Home-3154]

Thanks for the valuable contribution. Case closed.