I'm considering doing at least a partial drain. The water company I use charges for a minimum delivery of 5k gallons (so I assume I pay for that whether I wind up using it all or not). He can bring 6k to 6500 gallons per tanker. I don't want to wind up having to put in a few hundred gallons (or more) from my well if I'd drain out more than he has with him. So how does one begin to figure out the gallonage pumped out? I can rent a trash pump locally, but - short of eyeballing the level as it goes down - I imagine the pump doesn't have any sort of feature whereby it calculates the rate / gallons pumped out? If so, that'd make things easy. My pool walls taper in all the way around (compared to a square or rectangular shape where the walls are straight all the way down). So that makes it a bit harder to 'guesstimate' the amount pumped out. There must be, proportionately, more water at the top 2-3 feet (where the walls are still basically straight) compared to when everything tapers in (significantly) leading to the drain. Before I'd do this, I need to have a handle on how much to pump out given the 5k minimum delivery and the total 6k to 6500 load. 6 years ago things were easy cause I had the entire pool drained prior to renovation. I really didn't want to drain all of it this time nor have them bring two tankers though I guess that's a possibility. Any advice?