Whale pump pulsing

It is to reduce the chance of  air locks in the system.  Pulsing would indicate that air is in the hot system.  Check the security of the jubilee clips on the hot system or you may to to adjust the pressure valve, instructions should be in your handbook.  Or the '0' rings need to be replaced.

I've ordered new O rings. I don't understand why removal of the inlet socket will reduce the risk of air lock. 

I agree. The submersible pumps (both Whale & Truma) even have a stowage point while you take the aquaroll to fill it.

I did say 'reduce' not remove the risk of an airlock as by putting pump into water before connecting to caravan should allow water to enter pump and part of pipe.  But I am not an hydraulics engineer! My experience has been that if the water system is empty, after filling the Aquaroll and connecting the pump when I turn the pump on if it just runs without pulling water I disconnect from caravan and jiggle pump in water it always solves the problem.  Rarely happens when just refilling Aquaroll.  Hope the O rings solve the problem, I always carry a spare set.

Thats why I don't get the MUST be removed instruction, I've rung Whale but no response yet..

I’ve enquired and researched lots of issues surrounding caravaning over the years, reaching the conclusion that much of the expert advice comes from people who don’t know. That’s in part because they aren’t actually caravaners.

Unplugging the hose from your van before dropping the pump into your refilled barrel is a good example. Another gem is that Alko Trailers can’t explain how to avoid the road chafing their standard length breakaway cable when you’ve attached it to a fixed point on a tow bar where that fixing is close to the ball hitch. Fascinating too is their advice not to lower one corner steady at a time - synchronised winding with your spouse on the opposite side is obviously required. I love too, the way that an awning which costs hundreds of pounds is supplied with pegs too flimsy for a child’s garden tent.

I’d stick to your own common sense if I were you.

Mine is the opposite problem - pulses on cold, smooth flow on hot. Had our new-to-us 2015 Bailey Pegasus delivered to us on Friday, so still finding out where everything is (and where everything will stow away - very different from our previous van :) ). I'll check O-rings, and see how we go. Our old Carver system didn't suffer from that, and would always self-prime even from an empty system over the winter. Whale one seems less efficient, after a brief try-out. Not checked yet whether it is the Premium or High-Flow pump.

Hi have you calibrated the pump doing that seems to solve a lot of running issues!