Water hammer, a vibrating or banging noise inside of water lines, is a common issue in both residential and commercial buildings. Most of the time, water hammer is only fixed due to the annoyance of the noise it creates, but it can also cause a lot of damage to water lines, plumbing fittings, and surrounding building elements because of the movement it creates in the lines.
There are 3 main causes of water hammer: hydraulic shock, thermal shock, and differential shock.
Causes of Hydraulic Shock
Hydraulic shock is caused by the sudden stoppage of water flow. This is the most common type of water hammer, because it occurs in water lines servicing household and commercial sinks. Depending on the water pressure of the line, suddenly closing the valve will create the same amount of pressure in the opposite direction, which causes the noise and vibration.
How to Fix Hydraulic Shock
There are two common fixes for water hammer caused by hydraulic shock:
- Installation of a silent check valve
- Check Valves are installed on a water line to eliminate backflow. Depending on the length of a standard swing check valve, the time it takes to close the valve can cause water hammer, but a silent check valve closes when there is a loss of pressure, eliminating any hydraulic shock.
- Installation of a water hammer arrestor.
- A water hammer arrestor
- It is very important that the water hammer arrestor is adequately sized and installed in the correct location.
- A water hammer arrestor
Causes of Thermal Shock
Thermal shock is caused by a sudden change in temperature, which accelerates water flow inside a line. This situation occurs when steam mixes with water inside a line, which causes the steam to collapse and the water is accelerated. This commonly occurs in the condensate lines for steam systems.
How to Fix Thermal Shock
There are several known fixes for water hammer caused by thermal shock:
- Installation of an adapter that allows the drip trap to discharge in the direction of the condensate flow.
- This reduces the concentration of steam bubbles in the condensate line and minimizes water hammer
- Installation of a constant purge device in place of a steam drain
- These maintain a positive differential pressure across the coil, which prevents the entrapment of steam.
- Fix faulty steam trap
- Faulty steam traps dump steam directly into condensate line.
Causes of Differential Shock
Differential shock is caused by a low pressure liquid and high pressure gas existing inside the same line, such in high pressure condensate return lines.
How to fix Differential Shock
Generally, the way to minimize this type of shock is to decrease the pressure of the gas inside the water lines.
- Insulate the piping
- This is especially important on exterior systems. High heat causes water to evaporate, causing higher pressure.
- Make sure lines are sized correctly
- Lines sized too small will increase the pressure inside the line
- Install a drip leg in front of pressure control valves
- When valve is closed, high pressure gas pushes to the front of the line and when the valve is open the gas forces its way through, causing water hammer. Installing a drip leg allows the gas to have a path to escape
To learn more and view some very helpful visual aids, watch the video below by Armstrong International: