What kind of relief valve?
I did a lager or two in a keg (with a pull ring valve, not a one time valve) and was either fermenting or carbonating and I didn't have a blowoff tube at the time, and instead would pressure check every so often.
One weekend, I would wake up every few hours as I heard it let off gas somewhat explosively loud through the valve, though I didn't know what it was at the time.
It turned out pretty well, and those that tasted it thought it was just a standard lager. It was made with sorghum.
Secondary: GF Czech Lager
Waiting to be kegged, Italian Primitivo
Kegged&Ready: GF Orange&Coriander, GF Honey Lager, GF chocolate ale, GF English ale, Island mist (zinfandel), Island mist (cbry malbec).
Bottled: Infected Mead, Dry Hard ciders, Accidental Sorghumwine, various unnamed.