A damp spot -- or worse, a continuous drip from the ceiling overhead -- signals trouble. If you have a second-story bathroom, the problem could be in a water supply line or in one of the fixture drains. Fixing the leak could be as simple as replacing an under-sink trap or as complicated as cutting out a portion of the ceiling to replace drainpipe fittings. Finding the leak can be the toughest part of the task.
Types of Plumbing Leaks
If the leak appears as a damp spot that alternately dries and reoccurs on the ceiling above, it's most likely in a drain line. If the ceiling has a constant wet spot, or if it drips regularly, the problem is most likely in a pressurized water supply line.
Narrow It Down
Check the easiest-to-access spots first. This includes the water supply lines to the sink and to the commode, the sink trap and the wax ring beneath the commode. In the vast majority of cases, the leak will be at a plumbing connection where the water supply lines attach or at connector joints in the drainpipes. For water supply leaks, run your fingers over the lines to find out which one is damp. For trap leaks, turn on the water in the sink while checking the drain trap beneath for drips. Evidence of a leaking wax toilet ring might not show up on the bathroom floor, but this is a cheap fix, and if you can’t easily find the leak elsewhere, pull the commode and replace the ring. Once you remove the commode, you’ll see evidence of dampness around the toilet flange if the wax ring was leaking.
A shower should have a removable access panel, sometimes located in the room behind the shower wall, but tub drains, shower drains and the main drainpipe to which all fixture drains attach are often accessible only from beneath. If you’ve eliminated all other causes of leaks, the next step is to cut out a small access hole in the ceiling below. Cut out the section of ceiling drywall where you see the evidence of the leak. If a drainpipe connection is directly above, you’re in luck. Unfortunately, water can travel down a sloping drainpipe and then drip at a low point. If the leak is not right above the wet spot, you might have to cut out more of the ceiling drywall, following the drainpipe upward, until you find the leaking connection.
Fixing Water Supply Leaks
In some cases, the fitting between the water supply line and the fixture is loose and you can try tightening it. Sometimes, a washer in the fitting is worn out and you can remove the old washer and put a new one in to stop the leak. But, if that doesn’t fix the problem, the next step is to replace the entire fitting. Turn off the water at the main shutoff, remove the fitting and take it to the hardware store to find a matching replacement. Different types of lines require different methods of installation, so make sure you have the appropriate supplies before installing the new fitting.
Fixing Drainpipe Leaks
Most of today’s drainpipes are white PVC (polyvinyl chloride) or black ABS (acrylonitrile butadiene styrene). Some sink traps are chrome or brass, however, and it’s important to purchase replacement parts of the same type, the same configuration and dimension. Remove the old fittings and take them to the hardware store for comparison. Removing and replacing the fittings depends on the type of pipes. PVC and ABS joints require special glue and primer to attach the new fittings. Other types of pipes might need washers or require plumbing tape on the threads to hold them securely. The customer service rep at the store can assist you in buying the right supplies.
Sometimes the leak isn’t coming from the upstairs bathroom. Before cutting out ceiling drywall, check the rubber boot that seals the vent stack where it exits the roof. If the dampness appears only after a rain, it’s probably leaking around the rubber boot and traveling down the vent pipe. Alternately, an upstairs window could be leaking and the water traveling along interior framing until it reaches the spot on the ceiling.
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