Okay a couple of ideas. One, was the pvc glue and stuff you used potable? meaning it was drinking water safe? This is important as some might be toxic. The glue can will say that it is drinking water or potable safe......Two, the bubbles sometimes indicate an air leak somewhere in your system. Check and double check your connections if any air is getting sucked in you will have air bubbles. Also, a few bubbles will not hurt anything, most people don't like the bubbles as they can cause an undue amount of saltcreep. If anyone wonders if microbubbles are dangerous they need to read some of Eric Boremans or Robert Fenner's books on diving on open reefs where the waves crash constantly over the reef creating all kinds of air bubbles in the water........so....