Home and Garden | Installing Shock Arrestors - Plumbing

A loud noise heard after a faucet is shut or the washing machine or dishwasher turns off is most likely caused by water hammer. If the problem isn't due to waterlogged air chambers or loose pipes, then shock arresters (also known as water hammer arresters) will probably have to be installed into the system. These are mechanical devices that work by means of pistons or bellows. Shock arresters are available at plumbing-supply stores.

Each hot- and cold-water pipe going to faucets and appliances should be equipped with a shock arrester. The task will not be too difficult if pipes are exposed. However, concealed pipes will require the removal of walls.

Installing shock arresters
Below are guidelines on how to install a shock arrester to a pipe that is easily accessible.

PROJECT BASICS

Project: Moderately difficult
Estimated Project Time: 1-1/2 hours per arrester
Start Tips: Check if the water hammer noise is caused by a loose pipe or waterlogged air chamber before attempting to install a shock arrester.
Safety Tips: If soldering copper pipe in tight areas, put a protective metal sheet behind the pipe to protect the surrounding area from the propane torch flame.
Recommendation: Do-it-Yourself

TOOLS & MATERIALS

Tubing cutter or hacksaw	Solvent cement
Piping to match your system	NIOSH-approved respirator, as needed
Tee, nipple, reducing female adapter fittings
Mechanical shock arrester	For connecting copper pipe:
2 pipe wrenches	Reaming tools or round metal file
Safety goggles	Solder
Work gloves	Emery cloth
Clean cloths	Flux brush
	Flux
For connecting plastic pipe:	Propane torch
Utility knife	Spark lighter
Felt pen (for marking)	Clamps, as needed
Pipe cleaner, as needed	Protective sheet metal backing, as needed

Fig. 1

2) Cut and prepare the pipe
Use a tubing cutter or hacksaw to cut the copper or CPVC pipe (whichever your system uses) to accept a tee as close to the faucet or water-intake valve as possible (Fig. 1).

For plastic pipe, smooth the cut edges using a utility knife. Temporarily join the pipe and fitting together. With a felt pen, mark where the two pieces join - across the pipe and fitting, and then along the edge of the joint, overlapping the original mark. This cross will help you assemble the piece properly and quickly after you've applied the cement. Apply pipe cleaner and primer as needed, according to the manufacturer's instructions and local codes. Work in a well-ventilated area, and wear gloves and safety goggles; use a NIOSH-approved respirator if recommended by the manufacturer.

Copper pipe must be completely dry before applying flux. Remove residual water near the opening by placing sections of white bread in the pipe. The bread will soak up the water, and eventually disintegrate and flush through the system. Then smooth the cut edges, using a reamer, emery cloth and wire brush. Apply flux to the joining surfaces.

Fig. 2

3) Connect the tee
Wear gloves and safety goggles. Use a tee of the same material as your water pipes.

For plastic pipe, work in a well-ventilated area, and wear a NIOSH-approved respirator if recommended by the manufacturer. Solvent-weld the tee to the cut pipe. Apply the solvent cement to the joining surfaces, put the pipe and fitting together and slightly twist the pieces to distribute the cement and to align the marks you made previously. Hold the pieces in place for a few moments while the cement sets.

For copper pipe, assemble the connection so that the pipe ends fit firmly into the fitting. Solder the tee to the cut pipe (Fig. 2). Heat the pipe evenly first, using a propane torch, then apply solder in a continuous bead. In tight spaces, place a metal sheet in back of the pipe to protect nearby materials from the torch flame