I have had an autopot system utilizing the twin pot tray system of which I have 3 [6 pots] for many years . For some reason i cannot get the water to flow to the tray furthest away from the tank. the tank is about a foot higher than the trays. It is flowing to the first two trays OK but not the third. I have changed the filter in the tank although the water does not appear to be flowing fast through the pipes, it is just dripping out where the pipes connect to the T shaped connectors. Any idea on how I can sort please.