I have been hearing a clearly audible chattering in my hydronic heating system since a new boiler was professionally installed two years ago. The circulators, tubing and all valves associated with the boiler were installed at that time. The noise now seems to be louder - anyway, it is getting on my nerves. The noise sounds like it is coming from a Taco 241 Swet-Chek valve. The system has three zones (two house and one indirect hot water). Only one of the check valves is making noise. The one that makes noise is on a 1" house zone line that comes off the main line through a T but almost immediately takes a 90 degree turn through an elbow just before (3") the check valve. The other two zones are 3/4" lines, don't have any elbow before their check valves and don't make noise. While the tube size difference might suggest the cause of the noise is constriction or insufficient flow in the 1" line, I doubt it because I quickly get lots of heat in that zone. I think that the problem is turbulence from that 1" elbow causing the check valve to flutter violently. If so, the answer would likely be to move the check valve a couple of feet beyond any elbows. Any other thoughts about more likely causes and solutions? Thanks!