Hymer fresh water drain valve

[tonybvi]

Although I always drain down my Hymer Mli fresh water after every trip I realised today that I don’t really know what I am doing with the drain valve or how it works!!
It is one of those fancy valves with a triangular wheel on top of the tank which allows you to drain down to 25% by giving it a bit of a turn and to drain it completely by turning about 2 whole revolutions. It worries me that as I keep turning the valve it seems to give a bit of a jump and if I keep turning it simply keeps jumping. Although everything drains ok I wonder if this “jumping” is normal? Also when refilling I find that if I tighten the valve right down the fresh water drips slightly from the drain vent - easily cured by backing off the valve a bit.
Can anybody explain to me in very simple terms please how this type of valve works and what happens when it “jumps”?
Thanks
Tony

 

[The laird]

Although I always drain down my Hymer Mli fresh water after every trip I realised today that I don’t really know what I am doing with the drain valve or how it works!!
It is one of those fancy valves with a triangular wheel on top of the tank which allows you to drain down to 25% by giving it a bit of a turn and to drain it completely by turning about 2 whole revolutions. It worries me that as I keep turning the valve it seems to give a bit of a jump and if I keep turning it simply keeps jumping. Although everything drains ok I wonder if this “jumping” is normal? Also when refilling I find that if I tighten the valve right down the fresh water drips slightly from the drain vent - easily cured by backing off the valve a bit.
Can anybody explain to me in very simple terms please how this type of valve works and what happens when it “jumps”?
Thanks
Tony

Tony give phil a shout I’m Sure that’s the same system as his and he may b able to assist

 

[tonybvi]

Tony give phil a shout I’m Sure that’s the same system as his and he may b able to assist

Thanks. It’s not really assistance I need as I regularly empty and fill without problem. I just want to understand in simple terms how this type of valve works and what is happening when it clunks or jumps. On my van you have to be a real contortionist to even peer inside the tank, let alone study the workings of the valve. I have seen on another forum that this clunking/jumping is normal, in fact for a full drain down you are meant to open the valve until this happens - I would just like to know why!
Phil - any clues?
Thanks again
Tony