Solving Shower Leaks

Our shower upstairs is leaking down the wall to our basement. I've checked everywhere for leaks and it looks like it is in the plumbing somewhere between the shower and kitchen drain. I don't know what to do next except to start tearing the shower out and seeing if I can find the leak. What is your suggestion?
John W., New Hampton, IA

Shower leaks can be tricky to diagnose because there are many places that water can escape.  So, before you grab the wrecking bar, let's be absolutely sure we know where the leak is.

To isolate a shower leak, we need to start at the drain and work up.  Get a garden hose and run it directly into the shower drain.  Be sure to aim the hose so the water goes right into the drain, not across the shower pan and definitely not on any of the shower walls so you can be confident you are testing only the drain pipes by themselves.  Then run the hose and check for leaks.  If you find one, the leak is in the plumbing and you'll need to open the ceiling below to figure out where. 

If the drains pass the hose test, then the next thing to check is the shower pan.  Take a wash cloth and plug the shower drain.  Then fill the shower pan up with as much water as it can hold without overflowing (usually 3-5 inches).  Next, check the area below to see if it leaks.  If it leaks with the pan, but not with the drain, you may need to replace the shower pan, which is a time consuming, messy and costly job.

Now, for some better news.  If you have not been able to recreate the leak with either of the above tests, the leak is most likely due to voids in the grout joints or in the caulk seems which are easy to fix.  Very often, these leaks happen as water splashes off your body when taking a shower.  It takes only the tiniest void for water to work behind the walls and leak down to the space below.  Find that void and you will fix your leak, without the need to do any exploratory wall or ceiling surgery!

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how do you know that the

how do you know that the shower bodd is not leaking?