My Sprinkler System Rocks the House!

The banging noise you hear, known as water hammer, is a serious problem and will cause sprinkler components, particularly the solenoid valves to wear out prematurely or crack. Water hammer is caused by high water pressure which causes the water to flow at a much higher velocity then the equipment was designed to operate. When water flowing at a high velocity flows into a closed or closing solenoid valve the water has no place to go and will exert its energy on the walls of the pipe and fittings. Water cannot be compressed and it cannot flow backwards. If there is a check valve in the water supply, e.g. double check valve, then it will contain its force, its energy, to that segment of the pipe. The banging noise you hear is the result of the shockwave created on other components. The copper metal pipe distributing water throughout the house helps resonate that sound.

I usually see problems associated with water hammer when the static water pressure measures 70 psi and above. Surge pressures can exceed 10 times that amount eventually causing part failure and resulting in a flood. On sprinkler systems it is usually the solenoid valve(s) and I have seen them split, crack, and explode. Other valves in the home can be damaged by water hammer such as the solenoid valve in the dishwasher and washing machine. Fast closing toilet bowl valves can also cause shock waves in the system. Close any valve in your home manually to quickly and you can create water hammer.

Water pressure supplied by a municipality or water company can sometimes fluctuate. It's not always a constant supply. Water pressure can change due to demand by the public, service on the pump stations and wells, times of day; typically, water pressure is much greater in the early morning then during the day due to higher demand. Weekends in the spring and summer are much higher than during the week.

When a customer calls me with a water hammer problem I recommend one of the following:

1. Install a pressure reducing valve. This will allow me to set the maximum pressure that I require. Usually, for most homes and properties, I want 60- 65 psi.
2. Install a Water Hammer Arrester. This is a shock suppressor. It is a device with an air chamber inside and pressurized. When water hammer occurs and sends out its shock wave the shock suppressor absorbs the energy.
3. I design using smaller zones that use fewer gallons per minute. Less water flowing mitigates the shock waves.
4. Install smaller nozzles in the sprinkler heads. Less water flowing mitigates the shock waves.
5. Have your system operate later in the morning after you are up and about. There is more demand on the water supply from the public so there is probably less pressure available.

Preventing water hammer is important to preserving your sprinkler equipment, reducing maintenance costs, and preventing floods. The solutions listed above are simple, effective, and low cost.