Different types of beer posts?

[Jimrtl81]

I recently picked up an 11 litre Pepsi keg.
In the past I've only used commercial fittings and kegs so this little ******* is new to me.

I can't get the QD to seal on the beer post, it is definitely the beer post( no groove on the nut) and I'm using a new black QD.
Have replaced the post oring twice, but the QD is still a little loose and leaks.

I assumed it was a faulty QD but then I tried it on a different keg and it fit much more snugly and didn't leak.

Are there different types of beer posts or am I just an idiot?

Cheers

 

[MastersBrewery]

you may need to replace the popet valve, I'll assume you have lubed the oring when you replaced it. The other thing is if your using cheap QD's they can leak.