I have an old Hotpoint DF51. I've had the problem of it not filling with water twice now. I tried tipping it backwards etc, but the problem persisted. I finally fixed it by removing the filters etc from the drainage hole inside the unit. Then shoved a garden hose pipe a few inches down the waste pipe and blasted it for a couple of seconds. Hey presto. The blockage was cleared and everything worked fine. You'll need to turn the dishwasher on to drain the water of course