Underground Water Storage Tank Leaking - Advice Needed

[scz4]

It would seem since moving into our new house 6 months ago I post more in this section than the car sections

So.... I've got a water well which supplies a tank submerged under the ground. I started to notice some water sitting on the grass last week and tonight I dug down a little to see what was going on.

Now I've no experience of this type of setup after a series of new builds. As you can see, quite a lot of water sitting, but it's most definitely not coming from the lid. In fact, the water level inside the tank is a good 1ft+ lower than outside.

I went another 3 or 4 metres away from the tank and dug down, no evidence of water at the same water level.

I tested the buoyancy thingy and it's working just fine, it's not overfilling the tank.

Anyone know what's going on? What level are the in and out's generally on these types of tanks? I can only assume that's where it's leaking....

Edited by scz4 on Thursday 2nd July 22:14

Edited by scz4 on Thursday 2nd July 22:38

[tokyo_mb]

Inlet should be at the top, somewhere near the height of the ball valve you have in the picture.
Outlet likely to be at the bottom, unless there's a submersible pump that is pumping the water out, in which case it could also be at the top.

(Not a plumber, just based on the way my spring-fed, tank stored, pumped water supply works.)