Home > How To Stop Water Hammer

Bang, bang, bang.  No, your pipes aren’t possessed – you’ve got a water hammer or maybe air in your pipes, which isn’t technically a water hammer. So, how do you fix it? I’m glad you asked. Adrian Sanchez here, for Sprinkler Warehouse. Let’s get started.

What Does A Water Hammer Do?

First, let’s discuss what a water hammer is. Water is very heavy. When water is cruising through pipes at a high rate of speed and is suddenly stopped by a valve closing, all that mass slams against the valve.  That’s a water hammer.

Signs of a water hammer:

  • The noise occurs when a valve closes
  • Noise when the pump starts
  • Quick repeated bumps or a loud thump followed by silence

Signs of air in your pipes:

  • Noise unrelated to a valve opening or closing
  • Noise when a pump starts
  • Vibrating or prolonged noises

Yes, “Noise when a pump starts” made both lists. 

How To Repair A Water Hammer

So, how do I fix a water hammer? The easiest way is to lower the water pressure for your entire irrigation system. It probably won’t get rid of all of the water hammers, but it may reduce it to a level you can live with. One way to do that would be to install a ball valve before the backflow device and partially close it to reduce the amount of water entering your irrigation system. Of course, don’t reduce it so much that your rotors don’t operate properly.

If you have an automatic system, you may be able to stop the water hammer by changing the order in which your valves operate. Figure out which valve uses the least water; probably the one with the least amount of sprinklers. Then rewire the controller so that the valve that uses the least water is the last valve to run. You can also try installing a water hammer arrestor. These are installed upstream of zone control valves or a manifold. 

How To Repair A Water Hammer When The Valve Is Smaller Than The Pipe

If a valve is a smaller size than the pipe, there is a chance that the valve is the problem.  You should replace the valve with one that is the same size as your pipe. Additionally, cheaper valves often snap closed faster than more costly ones. It may be a good idea to replace the valve with a better quality one. Splitting valve zones is another good way to get rid of a water hammer. If only one of your zones is experiencing a water hammer, you can install a second valve and connect half the sprinklers to it. That will reduce the velocity and the water hammer should stop. Also, check for a “bottleneck” in your system. If there is a section of pipe that is a smaller diameter than the rest, it should be replaced with a diameter that matches the rest of the system.

How To Repair A Water Hammer When There’s Air In The Pipes

So, what about air in the pipes? One way to remove air would be to increase the water velocity to the point that it pushes the trapped air out of the pipe. To increase the water velocity in a mainline you need to manually open two or more of the circuit valves at once. You will need to let the water run for a while to get all of the air out. Be sure to close the valves one at a time. A pressure surge can occur if you close them at the same time and the surge could damage your irrigation system.

If there is trapped air in one of your zones, remove the three sprinkler heads that are the furthest from the circuit valve. Once you have removed them, open the valve and flush out the air. If that does not remove the trapped air, then try removing more sprinkler heads. Once the air is flushed out, put the sprinkler heads back on. If your problem persists after the next cycle your sprinkler heads could be at different heights causing the water to drain out of the pipes through the sprinkler heads.

If the water is draining through your sprinkler heads, it allows air into the pipes. If this becomes a problem you could install check valves at the inlets of your sprinklers.  But an even easier solution is to install a sprinkler head with a built-in check valve.

Remember, Sprinkler Warehouse has everything for your irrigation needs so your trees, lawn, flower beds, and gardens are lush and beautiful. Questions?   Chat with one of our superb customer service agents on They really know their stuff and they’ll get you squared away. Subscribe to our YouTube channel for helpful tips, tutorials, and general sprinkler instruction. For Sprinkler Warehouse, I’m Adrian Sanchez, the Sprinkler Warehouse Pro. Later irri-gators.