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Q: No matter what I do, my plumbing connection leaks water.

When doing an installation or making plumbing repairs it can be supremely frustrating when a plumbing connection leaks. You get everything put together, you turn on the water and you find a leak. You go back, retighten the fitting or even redo the connection and it still leaks. What are you doing wrong you ask?

You might not be doing anything wrong, sometimes fittings are just low quality or defective and there is nothing to do but throw away the fitting and use another. If the fittings are fine, then make sure you are taking all the appropriate steps to get a water tight connection.

Threaded fittings, whether metal or plastic, can leak if the threads are damaged by misthreading it on to its mate fitting. Once some force has been applied to tighten a fitting that has been misthreaded, the male or the female piece may be damaged beyond use. Carefully thread fittings and both inspect visually and use a sensitive touch to ensure the piece is threading properly before use any force to tighten the fitting.

Even when threaded fittings are joined properly, the space between the threads is wide enough to allow water to flow. Either pipe compound (aka pipe dope) or PTFE tape must be used used on the threads to create a watertight seal. See our articles on how to use PTFE tape or pipe dope.

If the fitting uses an integral part or washer, make certain both that the part is undamaged and properly inserted and seated in place. A fitting with a washer that is not properly seated may feel properly tight but the washer will allow water around it and cause the joint to leak.

Soldered copper joints can leak for a variety of reasons. First, the pipe and fitting must be thoroughly clean. A dirty surface will interfere with the flow of the solder and prevent a proper seal from being made. People often ignore the need for applying flux to the pipe and fitting. The acid flux prepares the surface and creates the best conditions for solder to flow into the joint.

Another common cause of leaking sweated solder joints in the mistaken belief that the solder is melted onto the fitting. When in fact the heated joint melts the solder and capillary action then draws the solder up into the joint. Read about how to solder copper pipe fittings.

When soldering a copper fitting, make certain to heat the pipe evenly, all the way around before applying any solder. The solder must flow in all at once, all the way around or the solder may leave gaps that allow water to leak through.

Finally, overheating a soldered joint can cause the pipe and fittings to distort or deform, in which case a tight fitting joint is impossible. If a joint is overheated, the fitting should be thrown away and the segment of pipe cut back a few inches before making a fresh attempt. Heat the joint so that the pipe becomes a bright copper but not changing color, nor black and sooty, and ease off as the flame passing pipe starts to turn blue-green.

Plastic pipes with slip-fittings use solvents to soften the plastic of the two pieces and then fuse together. Leaks from these joints can be the result of a crack in the fitting, improper preparation, wrong type of glue or just not enough glue.

Plastic pipe should be cut with square ends, all burrs should be removed, and the pipe should be cleaned with an appropriate solvent for the type of type you are working with. After the parts have been cleaned with a solvent, the glue should be applied. Use the included applicator to swirl around the pipe two or three times and covering the entire stub that will go into the fitting. Quickly insert the pipe into the pipe into the fitting while giving a quarter to half turn. This should yield a sturdy, watertight joint.

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