water pump

Depends what system you have.

If it is a pressurized system then it should be left on when vehicle attended. If it's an older van then it might not be ok to leave on and you only turn it on when needed.

its a 92 knauss traveller Ally. Im only turning it on as required.

We had an 07 knaus and it had a submersible pump. I would imagine that a 92 would have the same as most manufacturers started using external pumps around 2000.

If it is a submersible it might need primed. A lot of pumps are not self priming.
Check under the bench seats and find your fresh water tank, unscrew the cap on top. You will be able to get your hand onto the pump and hose under the water. Keeping it underwater and having the pump switched on and a tap open try jerking it vertically up and down until it runs more smoothly.

This should get rid of air in the system which can happen if the tank is run very low.

I have a mild tale of woe about water pumps. Mine is pressurised system with the separate pump. I normally will leave it on during the day as its a pain when you are getting off the toilet only to realise that the pump is not turned on for flushing and washing hands. I would normally turn it off at night.
When I had the van for a short while Eirebus noticed that the pump would click in every 20 minutes for a few seconds. He said that this was likely a small leak and the pump was restarting to compensate for a drop in pressure. As the van has a double floor I eventually checked underneath the top floor and discovered a very small leak which solved the problem.
Two weekends ago I was at Ballyboley on the Friday night and Drum Manor on the Saturday night. I woke from my drunken coma of a sleep on the Sunday morning and was still lying in the bed watching the TV when the pump came on full tilt. I turned it off checked the taps and sink etc and when turned on again it was running full tilt, I lifted the inspection traps to look in the basement but no signs of water. I went outside to look at the dump valves with nothing to see, but as I walked around the back to get into the van I could see water pouring onto the ground from both rear corners of the garage. I opened the garage door and discovered that the additional garage shower hose had become disconnected from the mixer tap and the water was gushing from it. I had packed the van back up again at Ballyboley on Saturday morning and hurriedly forced all that was under the awning (seats tables etc.) roughly back into the garage as the wind had got up and it was raining, and so may have unsettled the hose.
The water tank is very big, lasts 4 weekends and holds around 50 gallons, so had it happened a few hours earlier I would not have wakened from my coma and everything in the garage and in the underfloor compartments would have been soaked. Fortunately I hadn't bothered with the levelling ramps as it was only slightly low at the back and as the van floor is wood free no long lasting damage has been done.
Typing this has reminded me that 2 weeks later I still haven't put a jubille clip on the hose, but I have remembered to turn the water off at night and when I'm leaving the vehicle.