I posted this morning but it seems to have been lost in the ether!
We did a birth pool trial run about two weeks before the EDD. It took 15 mins to fill - we were living at the bottom of a hill from the water supply, so had great pressure. We also turned up the temp on the water heater after having turned it down for years for kid safety, so that we would definitely have hot water quick. The real thing also took 15 mins from start to finish - no way I would have been comfortable with an hour fill time!