Hello everyone- Here is a stumper for you....(I previously posted this in the homeowner section but never got a response; please forgive my posting here).... We recently moved to a new house and I finally had a chance to bring the irrigation system on line. It went fairly smoothly; one broken head and one that refuses to go down; and aside from replacing the damaged heads there is a bigger concern. When the system activates any of the zones, our upstairs toilet begins making the most horrendous pulsating noise and the filler tube begins pulsing water into the tank. The first time it happened I was outside and did not notice until an extra three inches of water was in the tank. It stops when you flush the toilet or depress the float enough to start some flow. I tested it with my wife and every time I activated a zone, it happened again. I can't imagine the previous homeowner experienced this as the neighbors say he used the system routinely. I am completely puzzled by this and have no idea what to do. The only other piece of information that could be important is that the water line feeding the irrigation system has an expansion tank on it. The valve to it was closed when I started up the system so I opened it after pressurizing the feed to the system but before pressurizing the zones. Any thoughts?