Two options to mimic cask ale and avoid spoilage with your setup:
1. Set regulator VERY low, appx. 3-5 psi to maintain serving pressure and freshness. At cellar temp, the beer will only carb to very low volumes. You can also use shorter beverage line.
2. Work out a gravity feed system by tilting your corny on its side angled toward the lid, modifying the diptubes, and feeding very low CO2 to maintain freshness. There's a great thread with photos on the site somewhere.
Not according to CAMRA standards, but a very close approximation.
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