Shower leaks when sprinklers on or toilet flushed
I have a tract house that is 7 years old. It was built using a product called Aquapex for the water pipes, this is clear plastic tubing that is supposed to be superior to copper.
My main water pipe comes in from the front, goes up the wall to the ceiling through the attic (with branches as necessary). It travels to the back of the house, back down the wall, and then outside to the hose bib/sprinkler valves.
Recently, when the master bathroom toilet (which is at the rear of the house, right before the line goes to the backyard) is flushed the MB shower will leak. It stops after the tank fills. Similarly, when the backyard sprinklers are on, the MB shower leaks, and then stops when they stop.
There is no evidence of water leaks in the attic or anywhere else.
Any advice on the source of this problem would be appreciated.