Had one at the last rented place. We became suspiciopus there was a leak after the meter when we had astronomical bills (several hundred quid a quarter), and then proved it by turning everything off and could see the meter still whirring around.
Took it up with water co; not interested and told that it was our problem. Took it up with landlord (as there was no leak in the flat it was clearly under the heavily-used drive between meter at boundary and flat). He was sympathetic but not looking to do anything (he was a builder) as it wasn’t costing him anything – told us it was our problem. After the next huge bill, I researched harder and found that water cos do have to eventually consider a partial refund if you have reported it. So to cut a long story slightly shorter I made a complete pain of myself to the water co whilst telling landlord I would dig up drive but as I didn’t know what I was doing it might be some time before it was finished…..! That had the desired result and he fixed it the same week (it was a massive leak) and water co eventually gave us a decent refund.
From the above, I personally wish I didn’t have to have one of the blasted things as I was considerably out of pocket for a long time (over a thousand quid) but from a wider perspective I suppose it was good as it eventually found the leak and saved valuable resources. The moral of the story is if you are renting you are always caught in a netherworld between landlord and suppliers. We had a similar problem at that flat with the gas meter which was reading cubic feet but the gas supplier thought it was cubic metres, but that’s another story.