I have a macerator which does a toilet, sink and shower in our basement, it has worked fine for 2 years then water started backing up into shower tray so I took the macerator out (3 hr job due to location) and the non-return valve had come a bit loose. Repaired that, gave it a good clean out and put it all back. Since then the toilet flushes fine but the sink and shower take, literally, an hour to drain. When they have water in air gurgles back up when I flush the toilet, before I strip it all out again, is there anything else it could that doesn't involve taking it out again (please, please please let it be so!!!)?