warning re.poor water pump performance

From day of sale our submersible   water pump in our Kemerton was hit and miss .Sometimes it would work ok , others led to a frustrating couple of hours trying to get rid of air from system etc . Even spent 5 days on a site using a kettle with all water switched off. A move from one site to another or just using the van off site for transport could lead to the system not working on return to site.. 20 odd years of dropping a Whale pump into a water barrel with caravans without issue  led me to believe that the air lock issue is a red herring and therefore I dropped the water tank and removed the pump. It is at  the bottom of the tank on the end of a semi rigid piece of pipe connected by push connectors so always under water. My issue was the pump impeller is an interference fit on the motor shaft . Sometimes it grips and pumps water at pressure other times pump could run all day and pump nothing as the motor turns but impeller slips on the shaft. 
       I replaced the pump and now everything works 1st time every time . One word of warning though. Autosleeper crudely fit the pressure cut off switch to the floor of the bed box. Unfortunately they fit a 90 degree push fit connector between switch and incoming feed pipe from the underfloor tank. The fitting is so close to the floor that the release ring on the push on fitting is activated and when water at pressure enters it forces the coupling apart so be aware as a flood would occur. Solution was to build the pressure switch up on a small block if wood so the fitting clears the floor. Water system now works as designed . Worth a look if like us you cursed the water system design.....while you are there it is worthfitting a small plastic box such as an ice cream tub over the vulnerable pressure switch as it lies in the firing line exposed to anything stored under the sofa.A cut out in the top of the box allows access to the switch control knob.