My problem was a bit different from yours.

Last time, my reservoir tank got leak, causing the water to FOREVER enter the tank and for 3 months, my water bill skyrocketed like crazy. Actually a very tiny crack at the bottom near the edge. Solution: put the silicon sealant (water proof) at it and problem solved.

But then again, it happened again. This time i suspected my water pump which i put near the main had caused the water pressure to hammer the tank and perhaps the check valve couldn't stand it. Some more, my water pump was faulty and in the end, i removed the water pump permanently.

Problem solved till today.

So yeah, i guess the water pressure being too strong is highly likely the main cuplrit.

You can go and saman SYABAS nao.