Posted by Harold Kestenholz - Hydronic Network on March 04, 2001 at 09:05:16:
In Reply to: loud knocking posted by Domenic on March 03, 2001 at 21:28:32:
The knocking may be from the zone valves. Try moving one zone valve lever to the open position for a day, then the other for another day. See if the noise stops on one day. Banging zone valves can sometimes be stopped by removing one of the springs inside the head cover of the Honeywell zone valve.