I'll try to help you out even though this thread does need to be moved...
The piranha is just a spyder clone and depending on where it is leaking from it could be a few different things. Take the frame, reg and volumizer off the gun. Pull the bolt and hammer out too. On the bottom of the body there should be flathead screw or something similar holding in the valve. Unscrew that and pop the valve out. Change the 2 orings on that and re-assemble the gun.
The other place it may be is the reg. Take a spare ASA and remove the macroline fitting and screw a gauge into that hole. Then unscrew the reg from the gun and put the pressure tester on the reg. This will allow you to check the output pressure and make sure the reg isn't leaking.