help with pump does anyone have a bailey olympus

Hi there, were just back from our first night in the van! all went well but we couldent get the water pump to stop leaking, which ment we could'nt really use the taps. After checking the manual it said when leaking at the y connector it ment there was too much pressure in the system but didnt give any indication on how to put it right. When we bought the van 3 wks ago on demonstration the pump worked fine so I'm guessing it's something were forgetting. we checked the water barrel cover had a gap for air and left tap open while filling like the manual suggested. Is there anything else we should have done? any info would be great thanks!