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How to Finish a Plumbing Job

Learn how to spot tiny leaks and flush debris out of pipes after finishing up a plumbing job with this expert advice from the job site.

Check for leaksFamily Handyman

Check for leaks

When the job is done and you’re ready to pack up your tools, take the time to do a final check for tiny leaks and sediment lingering in the lines. There’s no 100 percent prevention for either problem, but if you take a few precautions, you can reach 99 percent certainty. And that’s about as good as life gets.

Don't get fooled by condensationFamily Handyman

Don't get fooled by condensation

In high humidity, a cold water line will sweat, making it almost impossible to detect tiny leaks. Here’s how to work around that: Run the water just enough to fill the line. Then take a coffee break while the water in the pipe warms to room temperature. When it’s warm enough, wipe the pipe dry and look for leaks. Condensation may also be caused by cold water in drain lines.

Stress-test drain linesFamily Handyman

Stress-test drain lines

To test drain lines under a sink, don’t just turn on the faucet. Instead, completely fill the sink. (Fill both bowls on a double sink.) Then open the drain to release a gush of water. In humid conditions, fill the sink with lukewarm water. Cold water will cause condensation on the lines and prevent you from finding leaks.

Flush before you caulkFamily Handyman

Flush before you caulk

A small leak at the toilet flange leads to a puddle. But if that puddle is dammed up by caulk around the toilet base, it may not show up for months. So before you caulk, flush a couple times and probe for leaks with a strip of paper.

Detect drips with paperFamily Handyman

Detect drips with paper

Paper towels or newspaper are great leak locators. You’ll immediately see—or even hear—leaks as soon as a drip hits the paper.

Locate leaks with tissueFamily Handyman

Locate leaks with tissue

A wet spot on a tissue is a lot easier to see than a small droplet on a pipe. So wipe with a tissue and look at it after each swipe.

Check sink rimsFamily Handyman

Check sink rims

Dribble water around a sink rim to check the seal. Rim leaks rarely show up right away, so wait a few minutes before inspecting from below.

Flush out the sedimentFamily Handyman

Flush out the sediment

Water supply pipes contain sediment: corrosion, mineral deposits, pipe dope or solder. Plumbing work shakes that stuff loose. Water flow will carry that loose grit to fixtures—and possibly plug them. To prevent that, run water through the lines to flush out the sediment. Sediment trapped in a fill valve can make a toilet fill slowly or run constantly. To flush out this sediment, run water into a bucket before you connect the supply line.

What to do depends on the pipesFamily Handyman

What to do depends on the pipes

There’s no need to take every flushing step on every job. It depends on the age and type of plumbing. In a newer home with PEX plumbing, for example, you might only have to remove the aerators before flushing. Old galvanized steel pipes, on the other hand, usually contain a lot of debris and call for every trick in the book.

Start at a high-volume, low-risk valveFamily Handyman

Start at a high-volume, low-risk valve

To flush out debris, you need a high-volume flow of water. That makes outdoor hose bibs and washing machine supply lines great for this purpose. These faucets have another advantage too: Unlike kitchen or bath fixtures, they have big, simple ports that are less likely to get plugged or damaged by sediment. Just keep in mind that any faucet you choose for flushing should be downstream from the work area. Watch out! Washing machine hoses often have screens that can become plugged. Luckily, they’re easy to remove and clean. When flushing lines, you’ll be tempted to shut off the water after 10 seconds. That’s not long enough. One minute is the minimum. In a large house with long runs of supply pipe, let it flow for several minutes. Better to waste some water than to repair plugged faucets.

Protect the showerheadFamily Handyman

Protect the showerhead

Low-flow showerheads have tiny openings that can be plugged by a single particle. So run the tub faucet before the shower. In a dedicated shower (no tub spout), remove the showerhead and flush the line. Then, flush hot and cold separately. To get maximum flow through a single-handle kitchen or bath faucet, swing the handle to one side and run the water full blast. Then switch to the other side and do the same.

Remove aeratorsFamily Handyman

Remove aerators

Small particles that flow through a faucet often get caught in the aerator. So always unscrew the aerator and run the water after a plumbing job. Want more? Check out these top 10 plumbing fixes.