How to troubleshoot flush valves not closing

Purpose of flush valves

A flush valve helps keep your irrigation system clean by clearing out dirt and debris that can clog the emitters. As the system is pressurizing the valve lets water flush out any buildup, ensuring your plants receive even watering. After the sytem is pressurized, the flush valve can be manually flushed by pushing the nipple back in. 

Drip tape flush valves are generally only used on drip tape that is intended to be used multiple years. For single year use drip tape there are other options such as z-folds and end closures. 

Reasons flush valves do not close properly

Sometimes the flush valve is clogged with some type of debris that made it to the end. This could be a small piece of grass or a tiny pebble. Other times, the issue is that the water supply does not have enough pressure or the flow rate is not high enough to support the system. Below are how you would handle each situation. 

Solutions for flush valves not closing

When the flush valve is clogged, you can manually clear the debris by pressing the nipple on the end back into the housing. If the debris is too large, you may need to remove the flush valve and clear the debris from the back side. 

In the case that your water supply does not have enough pressure or flow rate, the easiest solution is to replace the flush valves with z-folds or end closures. Because drip irrigation generally is a low pressure and low flow requirement system, simply replacing the flush valves fixes the problem. 

If you want to keep the flush valves, a more time consuming solution is to manually turn each drip line valve on one at a time as they pressurize. A similar solution is to create a new zone with a separate header line and timer. This solution would allow you to keep the flush valves if you desire and automate the process. You will find it helpful to know your flow rate if you pursue the most complex and costly solution

You will need two pieces of data. One, you will need to know the flow rate of your water supply. To determine this, time how long it takes to fill a five gallon bucket with water from your water supply in seconds. Then make a copy of this file so you can edit the Google Sheet and input that time in cell A2 of the Flow Rate Calculator tab. 

Next, you will need to know the what your total system requires in terms of flow rate in gallons per minute. On the same Google Sheet, edit the cells outlined in red with the information of your system.

Once you know what your water supply and drip system GPM is, you will need to update do some simple math. For example, if your water supply flows at a rate of 4 gallons per minute, and your drip system requires 7 gallons per minute, you will need two zones. That is because your water supply can only supply half of what the drip system requires. 

Conclusion

Drip tape flush valves are a great product that extends the life of drip tape. When problems are encountered with them not working properly, focusing on the most simple solutions is recommended. Below is a bullet point summary for reference. 

Purpose of flush valves:

• Clears dirt and debris from drip tape, ensuring consistent watering.

• Manually flushed after pressurizing by pushing the nipple back in.

• Typically used for multi-year drip tape systems.

Reasons flush valves don't close:

• Clogs from debris like grass or pebbles.

• Low water pressure or insufficient flow rate.

Solutions:

• For debris: Manually clear by pressing the nipple or removing the valve to clean.

• For low pressure/flow: Replace flush valves with z-folds or end closures.

• More advanced: Manually pressurize drip lines or create separate zones with a header line and timer.

Flow rate tips:

• Measure water supply flow rate using a bucket and calculate drip system requirements.

• Adjust system zones if water supply can't meet system demands.