Free gas. 18 litre corny fill instead of 19?

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I would like to run corny's without bottled gas.

Does an 18l fill allow more gas space and over priming allow this?

I have an accurate reg on at the moment and after drawing a pint the pressure drops. Only to recover later.

Presumably the vessel is out of balance (after dispense) and the beer id giving up some dissolved gas to equalise?
 
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I suppose it's the same principle as a standard pressure barrel. You'll get the amount of c02 from whatever amount priming sugar you use. If it's still using up the sugar it'll keep priming,eventually it'll stop dispensing without glugging...letting air in...which you don't want. So you'll have to prime it again. If the keg gets really cold the c02 will absorb into the beer moreso making it seem it's gone flat again. But then you probably know all this!
 
I am sure there is a science answer but my gut feeling is that leaving more headroom would make no difference to how effective it is at dispensing under its own pressure..
 
I think this has legs. A pressurised water fire extinguisher is 100psi in the probably the top 15% of the vessel. It will empty and then hiss (positive pressure).

I know the pressure is higher, but I can't help but think for beer the concept holds together without repriming, but the ratio of beer to gas (space) will be different?

Even if it drops to a 12l fill, its worth doing.
 
If you don’t mind that the start of the keg is very carbonated and the end of the keg is barely carbonated then I guess it works up to a point depending exactly where those numbers end up. The no co2 solution I know of requires an air bag inside the keg that you can manually pump up to get positive pressure inside.
 
I recall a forum member (@terrym), while not being a fan of pressure barrels, advocated the addition of sugar as the barrel emptied and lost pressure. So if you could devise a gadget using a small bore syringe at one end and a gas quick connect at the other you could inject sugar solution into your keg through the gas post and create some gas for dispensing after a couple of days. Not free as you have to buy the sugar.
 
Not absolutely free I agree, but do think no cylinder/faff/rental/refill has its merits.

I do like the sugar injection idea. Gas post fitting, short gas pipe and a push fit valve. Easy to use just fill, close the valve and then push on.
 
If you don’t mind that the start of the keg is very carbonated and the end of the keg is barely carbonated then I guess it works up to a point depending exactly where those numbers end up. The no co2 solution I know of requires an air bag inside the keg that you can manually pump up to get positive pressure inside.

I do think that's a real risk but prolly only a pint at each end maybe? Dunno.
 
The whole keg setup is normally based on a steady carbonation and top pressure though eg the line restriction to tap. I suppose the worry is that you have several pints of just foam at the start. Still you haven’t spent more having a go than you would getting a cylinder anyway.
 
steady carbonation and top pressure
I think this is one of the main differences between cornys (with their gas cylinders and regulators) and pressure barrels (with their rubber band pressure relief valves and gas bulbs), while corny kegs have a “constant” pressure that can be monitored on a pressure gauge on the regulator, pressure barrels have a cyclic pressure profile, high immediately after gas charge and low after a few pints have been pulled. The sugar addition approach is likely to mimic the cyclic pressure profile. This could be reduced if a spundy valve (with integral pressure gauge) is fitted to the sugar primed keg. That way more sugar could be added as the pressure drops :confused.:
 
Not absolutely free I agree, but do think no cylinder/faff/rental/refill has its merits.

I do like the sugar injection idea. Gas post fitting, short gas pipe and a push fit valve. Easy to use just fill, close the valve and then push on.
Collect the CO2 whilst fermenting in a corny in a second corny, then use that collected CO2 to dispense the finished beer? Effectively you’d be making your own CO2 cylinder.
 
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