If an earthquake or an errant shovel bursts your irrigation pipes, you know it instantly. But smaller leaks can go undetected for months-- until you realize that your water bill has skyrocketed, or you've got a patch of soggy ground that won't dry out.
Bear in mind that aboveground leaks are likely only in drip, or micro-irrigation, systems.
Remove any mulch or ground cover that covers the supply pipe.
Turn on the water and check for spraying or bubbling.
Remember that an underground leak can occur with either a micro-irrigation system or a high-pressure sprinkler system.
Cap all the spray heads in the system.
Turn on the water and wait for puddles to appear on the surface of the soil.
Avoid digging in search of the leak--at best, you could unearth much of the system and have to spend time reburying the pipes; at worst, you could cut into a pipe and cause extensive damage. Instead, call in a professional who can use special equipment to trace the leak.
When you've located the source of the leak, dig a trench that's deep enough and wide enough so that you can work with the pipes easily.
Note the site of the leak. If the problem is a faulty seal in the pipe joints, simply tighten the clamps where the seepage is occurring. If the leak is in the pipe itself, proceed with the following steps.
Mend a leak in the pipe with a repair coupling (also called a dresser coupling). It consists of a coupling body, two rubber gaskets and two coupling nuts.
Turn off the water and cut through the pipe at the leak, using a hacksaw or plastic-pipe cutters (see A).
Separate the cut ends far enough that you can slip the coupling components onto the pipe ends. Slide a coupling nut onto each piece of pipe, then follow with a gasket. Slip the coupling body over one cut end, then insert the other end into the body. Slide a coupling nut and gasket onto each end of the body, and tighten the nuts (see B).
Flush the system thoroughly and check for any sign of seeping before reburying the pipe.
In the case of a major leak, or when connections have been pulled apart by earth tremors or frost heaving, you need to insert an additional length of pipe. First, turn off the water.
Cut out the damaged section of pipe, using a hacksaw or plastic-pipe cutters.
To mend PVC pipe, first clean the area to be cemented and dry it thoroughly. Then apply PVC primer and solvent cement according to the directions on the cement can (see C).
Slide a replacement fitting onto each end of the replacement pipe. Then insert it between the two cut ends, slipping an end into each replacement fitting (see D). Let the bond set for the length of time recommended on the can (usually 12 to 24 hours).
To mend a polyethylene (aka poly) pipe, slip a stainless-steel hose clamp over the pipe and insert the fitting. If the fitting won't slide in easily, soak the end of the pipe in warm water. Move the clamp into place over the ridged section of the fitting, then tighten it with a screwdriver.