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.

OK, so moving water causes your shower valve to leak. I can't imagine how but apparently it it does. The fault would be in the valve, not the piping. I am assuming by leaking you mean leaking out the shower head. What type of shower valve do you have?

Yes, the leaking is through the shower head. I don't know much about plumbing, what is the shower valve and how do I find it? The shower water control (H/C) is a normal kohler one, but I don't think that is what you are asking.

Thanks!

Yes that's your shower valve, two handle or one?

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.
Sounds like you have a Kohler valve with a faulty pressure balancing unit,(see image). Did you wish to tear into it yourself or are you going to call in outside help? Good luck, Tom

Yes, it is a kohler 1 handle valve. I would like to take care of it myself, but I am much more at home working on cars than plumbing. I am concerned about getting the assembly out of the shower without too much trouble, can I access what I need through the hole the valve handle comes through?

Overall, do you think an amateur with no plumbing experience can take care of it? I hate to pay a bunch of $$ for something I could have done myself.

Again, thanks for the feedback, this has been great.

Before we start to tear into the valve we better find out exactly what you have. Do you have any more information you can give me? Regards, Tom

I have the docs for the sink faucets, but apparently I never got the shower ones. Anyway, the sinks are Kohler Coralais series.

I found the closest ones I could find online that matched the look/style of the shower faucets, in the Coralais series, and got the following. Hopefully it helps.