Hi all, just bought 3 year old motorhome. First time we've taken it out I put about 25 litres of water in fresh water tank. On site, when I turn on any tap, the water pump pumps a little water through the tap or shower or flushes toilet but also pumps water out of a blue hose underneath the van (not grey water tank which is closed) ) Is this something simple that I'm missing or a more technical problem?