what moves when filling

[old sparky]

When topping off a PCP I hear a snap or pop then air starts to flow. What do I hear does something move?

thanks

[BackStop]

When topping off a PCP I hear a snap or pop then air starts to flow. What do I hear does something move?

thanks

Sounds like maybe the check valve in the pump or maybe the AG?

[USAFANG6799]

That's what I hear on my PCP's but it's more of a clicking noise. I'm sure the environment its in, be it open air, basement or a room, you hear the valve has an effect as to how it sounds to most.

[Gertrude]

check valve opening in the fill fitting on the guns air reservoir.
 It closes when you open the bleeder valve on your fill rig.

[KnifeMaker]

Yep! Exactly. ;<)
Knife

[be4meliz]

When topping off a PCP I hear a snap or pop then air starts to flow. What do I hear does something move?

thanks

If gun is empty, most likely the poppit slamming shut on valve- why some people with handpumps have a hard time filling  from empty- I have several that make a click when filling from empty.