Help with water tanks

Any info on problems with filling water tanks in my van would be appreciated.

During a recent trip to Echuca The van would not take any water when i tried to fill the tanks. My Van is a Majestic Knight and has Two water tanks. I opened both caps and tried this but the water kept spilling back out. In the end i had to buy a small piece of hose and fill it with a 2 litre jug...not impressed..

Mick Shrapnel, Vic