Hopefully this explains it...downpipe is about 10m to the right and feeds the 90mm pipe coming up from the ground in the bottom centre of the picture. This vertical…

Thank you very much, was wondering if that was my next option. I'd have attached a photo but it doesn't appear this forum supports it. Appreciate your advice…

Hi. Okay, downpipe is at the corner of the house. Travels underground (no visible wet areas) and surfaces 10m beside the tank rising to above the tank level.…

Hi, Not sure what you mean in the first question. If you mean literally overing it I think dirt then pebbles.
Only one downpipe services it.

Hi...chasing some advice 'cause I've run out of ideas. We have a charged water system and in the recent heaving Brisbane rains our water tank volume did not change at…