How to prevent and eliminate water hammer in home water heating systems? What causes the problem, what are the symptoms and how to fix it. What is the water hammer arrestor, how does it work and how to install one?
It is not uncommon for water heating and plumbing system to generate loud noise such as banging and thumping, especially when water stops or changes directions suddenly. This problem is known as water hammer, a phenomenon related to the hydraulic shock waves, which can cause vibration of plumbing pipes when they strike against each other or wooden beams.
The problem can be found in both new and old houses and no matter of the type of the plumbing; copper, CPVC or steel. Depending on the pipe type, the noise level varies.
Valves. What can cause water hammer to take place are a single lever faucet and a faucet with the solenoid valve, also washing machines and dishwashers, because they are equipped with the automatic valves that close fast.
Pressure. The problem can also occur when the water pressure from the main supply pipe is too high. Normal pressure is from 30 to 60 PSI and to avoid damages on the heater’s elements due to extreme pressure; it is recommended to install a pressure reducing valve.
There are several approaches on how to prevent or eliminate water hammer.
A water hammer arrestor, also known as an air cushion or air chamber, is a simple device where inside of its cylindrical body is pre-charged and sealed air chamber. The chamber is divided by the sliding piston. A side which connects to the plumbing is filled with water, while on the other side of the piston is air. Since the chamber is sealed, there will be no air or water leak. While the sudden water pressure increases, the sliding piston moves toward the air chamber compressing the air, so the vibrations will dissipate into this cushion of air, protecting the system from high-pressure shocks.
The water comes from the side which is connected to the plumbing.
The arrestor can also fail. The air chamber can become filled with water reducing its performance. Also, it can get clogged with the accumulated mineral deposits and debris, requiring proper cleaning.
Note: The air is factory charged. Some models are rechargeable, and some are not.
An arrestor for home use is easy to install. The arrestor should be installed near the water heater, as close as possible to quick-closing valves, and on the same pipe where the hydraulic disturbance appears. The arrestors are available for standard pipe sizes of ½” and ¾” or larger diameter. Due to the smaller size of the device, it can be easily installed inside a wall.
Arrestors can be installed in new and existing homes and plumbing systems, positioned horizontally, vertically or at any angle. Some models are designed for threaded applications, compression installation, with quick T-connect, brass adapter, for PEX and copper installation and other.
Follow the installation tips below:
Water hammer does not occur only in water heating systems. It can happen when running a washing machine, dishwasher or when flushing a toilet. The arrestors are the most common way of the water hammer repair and should be installed on the pipe where it occurs.