Now that you’re a soldering pro, let’s fix a banging pipe.
That irritating noise when you shut off a tap is often caused by automatic valves — like your dishwasher’s — which shut abruptly. Air chambers, which are capped-off pipes about 12 inches long extending above the supply stub tees of a fixture, trap air to cushion the shock felt by the pipes. Use pipe one size larger than the supply pipe.
Here’s a typical configuration and what you’ll require:
Solder the entire assembly together first, instead of trying to do it in a tight place. Always dry fit all parts to ensure a perfect fit.
Then, shut off the water system, drain it completely with a faucet, and leave a nearby faucet open so steam can escape. Cut the existing pipe, insert the assembly, and solder, being careful to keep the flame away from surrounding wood.
The heat draws any water in the pipe, and if you find the solder won’t take because of steam, try stuffing some white bread down the offending pipe to block it. This will dissolve when you turn on the water. (Make sure you remove mesh aerators in faucets before opening them.)
Note: If you attach new copper pipe to old galvanized steel pipe (called iron pipe for some reason), use a special fitting, such as solid brass, otherwise galvanic action between the metals will corrode the copper.