What does a bleeder valve do?

Sorry for the noob confusion. I searched around the forum and I'm still confused as to why I would need this. It's for checking the pressure in a keg...doesn't the regulator do that when it's hooked to the keg?
I bought a bunch of kegging stuff from a guy that was getting out of the hobby. It's more than I need so I'm going to sell off what I don't need so I can buy some kegs.
I saw one on Northern Brewer for 25$ without the quick connect so this should get me close to 1 keg but I don't want to let it go if i would need it.
Also it looks like the gauge is reading about 5 lbs right now. Is it ok that its at 5 lbs even though it's not on a keg or is there something wrong with it?
Thanks in advance for any help.

most people use it for fermenting in kegs. With the bleeder valve you can set a co2 pressure in the keg and use to carb late in fermentation. Saves you from having to use co2 tank to force carb.

So, I can hit it with high psi, wait for it to absorb, and then use it to check the psi? Am I understanding that correctly?

jts15 said:

So, I can hit it with high psi, wait for it to absorb, and then use it to check the psi? Am I understanding that correctly?

Click to expand...

If you use it late in late in fermentation then the co2 created by the fermentation will carb your beer. wortmonger has a great thread about doing this type of thing although he uses sankeys not cornies.

Oh, cool, thank you for the info. I'll have to find that thread.

A secondary use of this would be to put a certain pressure on your corny, then pop the valve on to check for leaks. If the pressure holds over time, there are no leaks.

I bought/built a couple spunding valves (IIRC, that's the proper term) like this, but I have adjustable pressure relief valves for them. I have yet to use them for their intended purpose due to a bunch of other more important things going on in my life.

A few clarifications.

I think some are mistaking a purge valve with a spunding valve. The device in the picture is for measuring pressure and/or manually releasing the pressure down to a certain level. If you've had a keg sitting a while, already carbed via force or priming, you can tell the level carbonation or "volumes" by measuring the pressure and temp. If the beer hasn't had time to fully equalize its carbonation to the head pressure, you'll simply be measuring the head pressure with no real indication of what the actually carbonation is.

A spunding valve is a valve that will vent once it exceeds a set pressure. It's usually adjustable. So... you could seal the primary vessel (if it's a pressure rated vessel) towards the end of fermentation and set the desired pressure on the valve so that it will carb.

I have something similar without the gauge and simply use it as an airlock when I ferment in a keg.