Update: Although I like the product and the concept behind the product, I cannot recommend that you purchase one of these.
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The CO2 injector attached to the Growler Saver. General operation instructions for preserving full or partially full growlers is to tap the CO2 injector and pull the PRV. This flushes the headspace. Another tap and you’re done. You can also force carbonate with this device. In that scenario you would tap the CO2 injector until the PRV vents. Full instructions will be included with production Growler Saver caps.
A Draft System CO2 adapter is also available. With that you can hook this right up to your kegerator.
To test the Growler Saver, I filled it with 24 ounces of beer. That’s just over 1/3 full. I put on the Growler Saver purged the growler and then gave it another tap for storage. Next I swirled the growler. Normally, CO2 in the beer would come out of solution into the head space until equilibrium is achieved. I let the growler sit, in the refrigerator, overnight.
The beer that is pictured was poured from a growler that was filled to around one third full, was swirled and then sat overnight. This beer was well carbonated in spite of that treatment because of the Growler Saver. I think this is a great product.
- Preserve growlers of beer.
- Force carbonate or re-carbonate beer.
- Save the last bit of a batch that won’t fit into a keg. Put it in a growler and force carbonate with this cap.
You could also make the case that the Growler Saver is a safety device. Get a growler filled with well carbonated beer at a local brew pub and let it warm up a bit. The pressure in this growler rises. At 60 degrees it’s around 25-30 PSI. The Growler Saver vents at below this pressure.