Water system problem.

Hello all, I am having problems with my water system on my 08 Nuevo EK. Had the van 5 years and never had the problem before. I am getting a build up of air in the system to a point where no water runs from taps. Hot seems to be worst affected. Have checked everywhere for leaks and found none, also checked under van and water tank. Have drained down three times and refilled, all seems to be fine for a day then, air starts to build up again especially after hot water has been on. Any ideas ?

I too, like rogerblack had a hairline crack in the pump inlet, if it IS your problem, a simple fix.

I assume you have a diaphragm pump with a water strainer on its inlet.  I experienced a problem when I didn't refit the stainer bowel properly and the O ring wasn't seated properly.  The water didn't flow properly and the system made a knocking noise because the pump was sucking both air and water.  Once I reseated the O ring all was well.