I just had to do the same thing on wed. I wasnt expecting needing one on this batch so the problem I had was all I had for a blowoff was my racking cane. That is about 1/4'' ID. It actually worked for a blowoff tube, but afterward i had a lot of crap in it. I kept running hot water through it and wasnt getting anywhere. Well I had to clean one of my kegs last night too so after I put hot water and TSP in the keg and pressurized it i ran it through my picnic tap which a also put my racking cane into. The hot water, pressure, and tsp cleaned it all right out.