Recently I had occasion, courtesy of my spouse, to change out the trim on the shower valve in our kids' bathroom. The project went very smoothly until I pulled the trim plate from around the single handle valve control. For some reason it had been caulked into place. Usually the trim plate is help in place by screws that attach to the valve body. I removed the old plate, old caulking, and re-installed the new plate. After finishing the whole assembly I discovered the reason for all the caulking on the old one.
Apparently the one-armed, special-ed, blind contractor (no offense) who had originally installed the valve assembly did not secure the pipes to a stud as required. Whenever I pulled on the handle to open the flow of water, the whole valve body (trim plate included) would pull out and create a gap between the plate and the shower wall. AAAUUUGGHHH!!!! Why do plumbing projects always turn into these kinds of nightmares? Is it just me?
So now I was faced with either using 18 gallons of caulk to hold the plate in place, or cut a huge hole in the wall to be able to reach and secure the pipes to a stud mechanically, or figuring out a different way to secure the pipes.
Using enormous quantities of caulk to hold it in place was out because I am not going to bet a happy marriage on it holding out until we move. Also I was philosophically opposed to jury-rigging it anyway.
Cutting a hole was out because this is a fiberglass unit, and the wall on the other side of the unit is the separator wall between my town home and the next unit. I didn't think I could ask our Korean speaking neighbors to let me whack a huge hole in their home to fix mine.
As I pondered my dilemma I was struck by an incident that had happened at my work. A forklift had hit a can of expanding foam that was on the ground. The resulting pop was funny until we had to get the dried, expanded foam off of everything. The stuff had amazing adhesive properties and blew up to about 3x its original size. I rushed out to my local home center and purchased a can. I inserted the dispensing straw into the hole that was cut for the valve body, and proceeded to let loose a fair amount of foam between the loose pipes and the fiberglass wall. I then re installed the new trim plate, leaving a little slack between the trim plate and the wall of the shower. I waited overnight, and then checked back. The foam had worked like a charm! The expanding foam had glued itself to the wall of the shower and the offending pipes. It had also expanded enough to pull the trim plate tight to the shower wall as well. I checked the operation of the valve, and it worked smoothly without the prim plate pulling away from the wall. I repeated the trick with the loose shower head arm in the same shower with equally good results.
If you are facing a similar difficulty I would recommend thinking about using expansion foam to get the job done. It is fast, easy, and very economical. Just be careful where you use it. If you put it somewhere it does not belong CLEAN IT UP IMMEDIATELY!! If you wait, you will have a nightmare job of scraping it off when dry. Also think about how much expansion you want. There is standard expansion, and a 3x expansion formula out there. There is also a soft expansion formula, but for securing pipes, the flexibility it retains after curing would be more of a liability than a plus. The other formulas dry to a hard, smooth foam that will tolerate pushing and pulling with out moving if you use it right. To my knowledge the only other drawback to using the foam is that it generally comes in a BIG can, and for a small job that means a lot of waste as once you start using it you cannot store it. Hilti has addressed this issue by using a fold back straw that allow you to use a portion of a can, and then store the rest for later use. A simple solution that allows those of us with only occasional use for expansion foam to not waste product or money.