Nrvs And Flat Beer Questions.

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Hi folks.

Got back from hol's on Sunday morn and found my CO2 bottle empty. :(
Should have it back, full, tomorrow.

Couple of questions:

Re. NRVs - I take it they only prevent fluid (beer) from flowing back through the gas lines and not gas? Is this correct?

Secondly, when I left I had 2 partly empty cornies and one full one in keezer. The 2 part full ones were fully carbed up. The full one was supposed to carb up while I was away. The freezer holding them would have kept the beer @ about 4c. Will the beers be completly flat, as fizzy as they were before I went away, or somewhere in between? None of the kegs have any pressure left in them, but I'm hoping because they have been kept cool that a fair bit of CO2 will have remained in solution.
Non-return valves are basically one-way valves. If installed correctly, they will allow gas to flow from the bottle, but not let gas or beer from the keg flow back though the regulator.

The beers that were kegged should have the same carbonation before, unless there is a leak somewhere on the keg side (ie: kegs, keg seals, disconnects, or gas line on the key side of the nrv.)

If you have a leak here, you may find your kegs flat. Best way to find out is do some 'quality control' or 'tasting' of said kegs.

To find a leak, fill a spray bottle with a mildly soapy solution, and spray anywhere on and around the kegs and lines after the nrv

unless u have a leak in ur system somewhere, I would of thought it would equalise out at around the same pressure the reg is set at in ur CO2 bottle and ur kegs.

I would guess ur systems has a leak sumwhere seeing as though ur CO2 bottle is empty and ur kegs have no pressure. therefore it is likely that ur beer could be likely carbed from what hasnt escaped the beer, if not flat.
NRV should prevent both gas and fluid flowing back to the reg.

The amount of carbonation depends on how long the gas has been off and the size of the leak (which it sounds you have). Even though it's kept cold, CO2 doesn't want to be in solution, it only stays in there (and gets absorbed) due to the head pressure provided by the gas bottle.

When you get the bottle back, spend some time checking for leaks - I had a leak on a barb due to a tight bend radius on the beer line near a fitting. When the line was straight and not applying pressure on the barb there was no leak, but as soon as I applied a bending pressure some gas escaped.
Thanks guys.
I definatly have a leak somewhere, I suspect my manifold / one of the joiners attaching it, as I only recently fitted that and had no problems beforehand.
I replaced all the seals in my kegs when I got them, late October. I then pressurised them, and they all kept pressure for some weeks, until I released it to fill them.
Think I might ditch the manifold and go back to basic line splitter, Tee's and one JG NRV. Was nice being able to force carb a keg and just shut the gas off to the others until they needed a bit more for serving though.