N/A PCP air pressure retention?

expected Indefinitely......
Reality several years......
if it goes low in several months, there is a tiny leak, may not be an issue for most people.
if it goes low in several days, there is a small leak, to most it is an issue and needs to be addressed.
if it goes low over night, there is a big leak. find and fix leak.
if it goes low in several hours, there is a very big leak, find and fix leak.
if you can hear the leak, it is a huge leak, find and fix leak.

in most cases it is usually a bad O-ring that needs to be replaced, if leaking out the barrel it is possibly a Bad Poppet valve depending on the Brand and Model, some times a few drops of Silicone Oil in the filler hose or probe will blow lubricant into the pressurized section of the gun and lube the O-rings and sealing the leak if O-rings are Dried out
but in most cases, a replacement of O-rings will be Needed, when replacing O-rings, use Silicone grease or Silicone oil on the O-rings to keep them from drying out.
If you have a suspected leak, just say so on this Forum, give a good description of what is happening and the make and model of the gun is very helpful, also the type of fill port on the gun would help too.
 
expected Indefinitely......
Reality several years......
if it goes low in several months, there is a tiny leak, may not be an issue for most people.
if it goes low in several days, there is a small leak, to most it is an issue and needs to be addressed.
if it goes low over night, there is a big leak. find and fix leak.
if it goes low in several hours, there is a very big leak, find and fix leak.
if you can hear the leak, it is a huge leak, find and fix leak.

in most cases it is usually a bad O-ring that needs to be replaced, if leaking out the barrel it is possibly a Bad Poppet valve depending on the Brand and Model, some times a few drops of Silicone Oil in the filler hose or probe will blow lubricant into the pressurized section of the gun and lube the O-rings and sealing the leak if O-rings are Dried out
but in most cases, a replacement of O-rings will be Needed, when replacing O-rings, use Silicone grease or Silicone oil on the O-rings to keep them from drying out.
If you have a suspected leak, just say so on this Forum, give a good description of what is happening and the make and model of the gun is very helpful, also the type of fill port on the gun would help too.
Well done!
Mods need to make this a sticky thread. If it fluctuates in pressure any more than thermal expansion allowance, it goes in your "issue to most" resolution category.
 
That is what I intuitively thought. I traded PCPs with a fella and I got the leaker. Now I have to get my divining rod and find the leak or just tear the whole thing down. Slower leak, holds enough air for a couple or days but ever so slowly loses all its pressure. Kuzey K600 .177.
there is only so many places an air gun can leak, get some leak detector and you shouldn't have too much trouble finding the source of the leak.
 
Years. Until something fails. If you're loosing air, you have a slow leak. Usually caused by a bad o ring or bad fill valve.
Funny that you bring up fill valve as a potential place to leak. I was going to do some shooting a few days ago, so I topped off my RTI. When I opened the bleed valve on the compressor, instead of the usual psst. I got a constant leak. Disconnected the fill line and the foster fitting on the gun just leaked the gun dry.
Set the RTI aside to deal with later and grabbed my TalonP. Topped it off, opened the bleed and same as the RTI. Two Foster fittings in a row. Go figure.

Both fixed now and all is well in my world.

As for slow and hard to find leaks, both of my guns are pretty simple, and I keep a couple complete sets of o rings on hand, so rather than chase a leak, I think I would just do a complete reseal.
 
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