How to fix leaks when valves are off

When water flows onto your sidewalk or curb after you turn your irrigation system off, but then stops after a few minutes, is called Low Head Drainage. Usually this issue occurs when the irrigation system has been installed on a slope. A change of elevation of less than a foot will often create Low Head Drainage. Once the sprinklers are turned off, the water in the pipes drains out via the lowest elevated sprinkler head and then is replaced with air.

Is it a leaking valve or Low Head Drainage?

If the system is off and water is continuously flowing from the sprinkler head, then you have a leaking control valve. The main difference between Low Head Drainage and a leaking valve is that Low Head Drainage results in water leaking from the lowest elevated sprinklers for a while after they run, but then the leakage stops after the pipes are fully drained, which may take several hours. If a valve is leaking, then the leakage will continue to flow all the time without stopping. Look for moss or algae growing on the walkway or the curb. This is a common sign that your control valve is leaking.

How to fix a leaking valve:

Disassemble the valve
Clean it
Replace any bad parts
Reassemble the valve
If you determine that the valve needs to be replaced, click here to read how you can do it yourself.

How to stop Low Head Drainage:

To stop Low Head Drainage, you need to have special anti-drain valves installed at the sprinkler heads. Now in some cases valves are built into the sprinkler head. It is an optional feature when you purchase the sprinkler and is available on most major brands of sprinklers. Most people just simply purchase a new sprinkler head with the check valve feature and replace the old with the new.

As another option, you can buy separate check valves and install them on the pipe under the existing sprinklers. Although much harder to install, it will accomplish the same effect. You will need to dig up the sprinkler head, remove it, install the new check valve on the riser and then screw the old sprinkler back into the new check valve. You will then need to lower the sprinkler head to the appropriate level since the check valve will raise the sprinkler about 3 inches. Also, the pressure typically drops about 2-5 psi in this instance.