Take it off the rifle (can either remove the barrel and unscrew it, or remove the gas block and then unscrew the tank).
two set screws around the regulator body need to be backed out.
Unscrew the regulator.
The pin of the pin valve is a brass part (and a spring) that sits on top of the brass piston inside the regulator...be careful it doesn't fall out and get lost.
Brass piston is surrounded by a bunch of cone washers (that supply tension). Can lift it out as a unit (with the cone washers captured on the brass piston).
Check the little end of the brass piston...has a tiny little delrin seal on it which fits on a raised "tittie" at the bottom of the regulator..this is what seals the tank.
Remove the brass piston and cone washers (will come out as a unit) and clean the inside of the regulator with a Q-tip. Can clean the bras piston as well if it looks "funky"
If that delrin seal on the small end of the brass piston is cut, abraded, or just clogged with crap, it won't seal and the air will leak slowly (causing that "creep"). best choice is a replacement (JDS sells them). It;s such a tiny delrin seal, and kind of roll crimped into place, that replacing it is not really a great option....can be done, but the failure rate for the attempt is pretty damned high.
The piston also has two o-rings (one at the small end and one at the big end). Clean them and lube them LIGHTLY with Silicon grease (and check that they aren't abraded or otherwise screwed up).
Now if you want to spend the extra $, look at paintball supply for a Bob Long filtered fill nipple to replace the one on the HPA tank. Something like $22-$25, but that includes a screw on metal nipple cover. That nipple has a built in filter (think it's a 5 micron filter) which can block most of the grit/funk from getting into the tank (and into the regulator) when filled.
Have to mention: Have been running 5 HPA tanks for about 2 years, and i shoot the hell out of these guns. Only one tank has given me any trouble. From my fiew point, the 2 year problem rate is about 20%.
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