Keeping water from leaking inside the wall
I like checking myself and this is a common question asked by clients. A small hole is the drywall is an easy repair and the piece of mind it offers many is priceless. Plumbers are tougher and trust their skills. We do not have their years of cofiendence to draw on so an inspection is not over the top.
With a large diamond coring drill bit you can pre drill a scrap of tile or plastic. Then place this around the small hole. Use the pre0-dilled piece to hold the drill bit in location and drill a larger hole. You can then give yourself a little room to look. Make sure the trim of the shower arm covers the hole.
These drill bits are a good $40-$60.00. Using a larger hole when cutting the tile in the first place can avoid this tough check. We have been waterproofing these shower arm wing backs to leak outside the shower tile's assembly. Pretty slick what you can do with off cuts of membrane and some random PVC fittings.
How to fix a leaking shower arm inside a wall.
My buddy renovated his home and last year he called me over this very same concern. Turns out the plumber (apprentice) installed the shower arm with only 1 full turn. The very first shower flooded out the laundry room and damaged the ceiling of his new place. I went down and used my inspection camera which I snuck up inside the wall via the cover plate on the control valves.
I think enough people have heard this horror story once before to understand that checking is not such a bad thing.
Preventing leaks inside shower walls
It is science. Plumbers go to school for this and then study in the field logging hours and hours of time on the tools.
Originally Posted by Hardt
There is too much to learn and so much can not be learned online or by books.
Careful you don't tighten up a plastic shower arm to much - they can split or crack so easy.
In Canada you are required to pressure test these bathroom set ups before the walls get covered with board and tile. Leaks show themselves quickly under 200 pounds of pressure. I would never skip this step and require any plumber to do this test - required by local code or not. I understand parts of the US follow this same procedure.
A plumber might comeback and fix a leaking fitting but if you have a leak and the leak is the result of a failed connection or fitting. Who pays for all the damage? The plumber? The wholesaler who sold the part? The manufacturer of the part? Who....
Why go there. Crank up the pressure and isolate the new work. I see all to often plumbers changing out shut offs and redoing connections because the work crapped out under a 200psi pressure test. Happens all the time - it's why these tests are required in Canada and parts of the US. JW