How to Install an Air Chamber to Prevent Water Hammer

First, identify the source of the water hammer. The banging sound is caused by a shockwave when a valve closes quickly. Operate one fast-acting valve at a time, such as a washing machine, dishwasher, or a single-lever faucet, to pinpoint which line is causing the noise. The air chamber should be installed on the problematic supply line (hot or cold), as close as possible to the shutoff valve for that fixture.

Turn off the main water supply valve for the entire house. This is typically located in a basement, crawlspace, or utility closet near where the water service enters the home. After shutting it off, open the lowest faucet in the house (like a basement sink) and the faucet closest to your work area. This will relieve the pressure and drain most of the water from the system. Place a bucket and have some towels ready directly under the section of pipe you will be cutting.

Using a tape measure, measure the central body of the 1/2-inch copper T-fitting (from the inside shoulder of one opening to the other). Mark this length on the copper pipe where you intend to install the air chamber. Attach the tubing cutter to the pipe, aligning it with your first mark. Rotate the cutter around the pipe, tightening the knob slightly with each rotation until the pipe is cleanly cut. Repeat for the second mark. Use the deburring tool, often attached to the cutter, to smooth the inside and outside edges of both cuts.

Thoroughly clean the outside of the two cut pipe ends and the inside of all three openings of the copper T-fitting using emery cloth. The copper should be shiny. Also, clean one end of your 12-inch pipe section and the inside of the copper cap. Once clean, use a flux brush to apply a thin, even layer of soldering flux to all cleaned surfaces. Assemble the pieces for a 'dry fit': slide the T-fitting onto the pipe ends and insert the 12-inch air chamber pipe into the top of the 'T'. Place the cap on the air chamber pipe. Ensure everything fits snugly and is aligned correctly.

Place the fire-resistant cloth behind the work area to shield walls and other materials from the flame. Put on your safety glasses and gloves. Light the propane torch and begin heating one of the T-fitting joints. Heat the fitting, not the pipe itself, moving the flame constantly to distribute heat evenly. When the flux begins to bubble and smoke, touch the tip of the lead-free solder to the joint seam, opposite the flame. The hot fitting will melt the solder and capillary action will draw it into the joint, creating a complete, silver ring. Remove the solder and then the flame. Let the joint cool without disturbing it. Repeat this process for all three joints on the T-fitting and the cap on the air chamber.

Once all solder joints are completely cool to the touch, close the faucets you opened earlier to drain the system. Go back to the main water shutoff valve and turn it on very slowly. This allows the pipes to fill with water gradually, which prevents another shock to the system and makes it easier to spot small leaks. Return to your work area and carefully inspect all the new solder joints for any signs of water beading or dripping. Use a dry towel to wipe the joints, which can help reveal very slow leaks.