Stopping water hammer in your irrigation system often comes down to managing water flow and pressure, especially at the point where the problem originates.
The most direct solution, particularly when the issue stems from a single irrigation valve, is to manage the flow rate for that specific zone.
Addressing Water Hammer from a Single Valve
Water hammer occurs when flowing water is abruptly stopped or forced to change direction, creating a shockwave back through the pipe. If you notice this knocking or banging sound only when a particular zone or valve turns off, the problem is likely isolated to that part of your system.
Based on the reference provided, if only one of the irrigation valves is causing a water hammer, the easiest solution is to reduce the amount of water that the valve is using.
That will reduce the velocity and the water hammer should stop.
How to Reduce Water Usage for a Valve
To effectively reduce the amount of water a single valve is using, you need to lessen the demand placed upon it. The reference specifically advises: You then need to reduce the number of sprinkler heads the valve operates.
Here's how this practical step helps and how to implement it:
- Why it Works: Each sprinkler head requires a certain flow rate (gallons per minute or GPM) to operate correctly. When a valve controls multiple heads, the total flow through that zone's pipe is the sum of the flow for all active heads. By reducing the number of heads on that valve, you decrease the total GPM demanded by the zone. A lower flow rate means lower water velocity in the pipe. When the valve closes, this reduced velocity results in a less intense pressure surge, mitigating or eliminating the water hammer.
- Implementation Steps:
- Identify the Problem Zone: Determine exactly which irrigation zone and valve trigger the water hammer when they shut off.
- Count the Heads: Note the number and type of sprinkler heads connected to this specific valve.
- Assess Total Flow: Calculate the approximate total GPM required by all heads on the zone (check sprinkler head specifications if possible).
- Reduce the Load: The goal is to lower the total flow. This might involve:
- Redesigning the zone to remove several heads and potentially adding them to a different, less-loaded zone.
- Splitting the existing zone into two smaller zones, each controlled by a new valve, thereby distributing the load.
- In some cases, adjusting specific heads might slightly reduce flow, but removing entire heads is more effective for significant reductions.
- Test the Zone: After reducing the number of heads, run the zone again to see if the water hammer has stopped.
Reducing the number of heads directly lowers the water velocity in the pipe for that zone, addressing the root cause of the hammer specific to that valve.
Summary Table
| Problem Area | Recommended Solution (Based on Reference) | Mechanism |
|---|---|---|
| Water hammer from one valve | Reduce the water usage of that valve | Lowers water velocity |
| How to achieve this | Reduce the number of sprinkler heads | Decreases total flow requirement |
Focusing on reducing the load on the specific valve causing the noise is the most direct and easiest method when the problem is localized.
