When you find reduced water pressure in one or more of your lawn sprinkler system heads, or when you find soggy areas of your lawn that don't seem to dry out, these can be signs of a leak in your sprinkler system. You will need to locate the pipe or sprinkler head that is leaking and repair it.
Step 1 - Determine if a Leak Exists
Chances are good that if you have a small leak, the only way you'll know it exists is when you find a reduction in pressure at sprinkler system heads when the system is turned on, or you'll find excess water somewhere in your system. If, for example, your system pipes are running close to the foundation of your home, and if you were to see underground water leaking through your home's foundation, this could be evidence that a sprinkler system pipe is broken. You may also see evidence of leaks in pooled water or soggy patches of lawn in places where such water should not exist.
Step 2 - Find the Leak
Once you've determined there is a leak in your sprinkler system, the next step is to locate the leak. If it is below ground, locating it will typically be a challenge, because you're not likely to see the actual leak. With your sprinkler system turned on, begin at your first sprinkler head and follow the heads through which water is flowing at its usual rate. When you reach the first sprinkler head with reduced pressure, this will tell you the leak is between this head and the previous one. Look for an area between these two sprinkler heads where water is bubbling up through the lawn, where the lawn is soggy, or where water is pooled.
Step 3 - Cap Sprinkler Heads
If you find equal water pressure at all system heads, chances are good that the leak in your system is too small to create reduced pressure in any of the heads. At this point, you'll need to increase the water pressure. To do that, turn your sprinklers off, replace all sprinkler heads using heads with caps screwed onto sprinkler risers. Turn your water on, and check to determine if there is reduced water pressure at any of the sprinkler heads.
Step 4 - Repair The Leak
Having identified where your leak is located, dig carefully until you've uncovered the sprinkler pipe or fitting from where the water is leaking. If the leak is coming from a bad pipe joint seal, tighten the seal clamps or replace the seal. If it is coming from a broken pipe or riser, replace the pipe where the break is located. When finished, turn on the sprinkler system, and check to be sure your repair has fixed the leak. Then replace the soil and lawn.