First off, dont use lube in a piranha, it causes problems like your having. Use ER oil or gold cup oil.
Do everything im going to list.
1. Clean your upper and lower tube with a squeege. When removing your valve, make sure you put in the right way. If its in the wrong way right now it could be the source of your problem.
2.When your hammer is out check the o-ring. If its a loose fit or not the blue o-ring thats your problem.
3. Check your bolt o-rings, once again make sure there not worn and loose.
4. Re-OIL all the o-rings, do NOT use lube.
The guns arent that complicated, that should fix your problem.
Piranha Evo,Ext and Gsx.