Westfalia lpg camping gas tank leaking

[Auto]

Hi folks yes my lpg tank is leaking from the on off valve were the threads screw in to the tank,
when I resored the tank I removed everything from it to paint the tank but when I came to re fit that tapered on off valve it turned beyond were it needed to be to mate up with the regulator and I didn't want to risk another rotation with the spanner incase I broke something so I had to turn it back a quarter of a turn to meet the regulator this left it slightly  lose and as I continued to connect the regulator and gas pipes it kept moving and as a result it leaked when I filled the tank only a little though.
I have now used the gas and have taken it back out to have another go at it but it was also leaking from that left hand thread gland nut on the regulator and today as I have taken it apart have noticed their isn't a sealing washer inside that nut at the bottom my question is should their be one I can't see how it could seal with out one as it would be just brass on brass ? 
I hope that makes sence please see the pictures below 
I'm sure I'm asking another question that now one can remember if their was one in theirs but I sent gunz a message and they can't help either as they don't have any in stock apparently 
so if any one can help it would be much appreciated 
cheers phil 

[Auto]

Right this is what I've done, I smothered it in that blue thread lock sealer, tried to get another full turn of the on off tap but try as I might couldn't get it to do another full turn so I took it back out again smothered it back up again and just tightened it until it faced the regulator, 
I then smothered the blue gunk inside of that big nut and the opposite piece on the on and off tap and tightend it until I couldnd get it any tighter, the on and off tap still moved a little as I connected the cover and things back on but hopefully that blue gunk will harden to seal and keep everything in place it does say on the tube the cure time is up to 24 hours so we will see next time I fill back up again,
if that doesn't work i will have to use PTFE tape may be I should have tried that instead I don't know
but still any ideas welcome if you care to chime in
cheers Phil  

[Mocki]

There is a rubber washer in the regulator to the tap on mine , not sure if its original , but there is .

[Auto]

Hi thanks Mocki so it sounds like mine is missing then I don't suppose you have a picture so I can find something similar  ?
or a description of were it sits to seal the big nut ?
I suppose it sits on the bottom flat part of that nut round the inner regulator pipe
cheers phil

[Auto]

Hi Mocki does this look the same as yours spotted them on Ebay so I think I'm going to get one only 99p
cheers phil 

[Mocki]

Yes thats about it , without taking mine to bits i would say thats the one

[Auto]

Hi Mocki thanks that's great I splashed out and bought 2 ha ha  !! 
I think I'm going to take it all to bits again and use PTFE tape next time it might fill the gap up better between the tank and the tap threads
giving a tight fit when the alignment for the regulator lines up, I will see and decide tomorrow if that blue gunk has cured or not
but I can foresee it getting loosened trying to get that regulator not lose
any way thanks again 
cheers phil  
 

[Mocki]

Can you not start the thread at a different angle ? I seem to remember that when i fitted (REfitted) my tap it ended up “out of line” and i toook it off and started it 45° Different , I’m sure I’m not mis remembering this ????

[Auto]

Hi Mocki yes your right the thread will start and end at the same point, but in this case this thread is also tapering 
I don't know for sure and this is only my thoughts,  if by wrapping that taper with PTFE tape it increases it's size slightly it may tighten 
at slightly less resolutions than mine currently does insted of being sloppy with the liquid sealer which I noticed all squeezed out when I tried to go another full revolution but only managing half a turn,  then when I took it out absolutely nothing was left on the threads they were totally clean again so all it would need is half a turn earlier which would be perfect in my case 
it's all just trial and error and may be I've expanded the hole by over tightening I don't know I'm not exactly the hulk but I did get angry
but not that much I don't think, nothing broke and no shredded clothes so far , I will try again later ha ha !!!
cheers phil