We have at our house and aerobic septic system. This means that the water gets separated and processed and purified and pumped out through sprinklers in the back yard, while the yucky stuff stays behind in the tank. It's an efficient system, and works pretty well.
Except when it doesn't.
We've noticed that while one of the sprinklers has been spraying correctly, the other one has been sporadic, and recently stopped working all together. This triggered an alarm condition on the system, and we called the maintenance guy to come take a look.
He fixed a problem with the pump, and then went to look at the second sprinkler. Nothing was coming out, even though the pump was working and the first sprinkler was going great guns.
So he took the sprinkler head off. Nothing.
Assuming this must mean a rock or something was plugging the connection, he dug up the end of the pipe and cut it off.
Since this fix-it guy charges big money per hour, and the problem was obviously in a piece of PVC pipe between two known points, I decided to tackle the rest of the job myself.
Armed with rubber gloves, several shovels and a pipe cutter, I found that the check valve - a little one-way flow regulator that keeps the water from running backwards - had turned into a no-way flow preventer.
So after a trip to Home Depot and $15 worth of bits, both sprinklers are as good as new.
Now if only the same could be said about my bending over and digging muscles. Oooh - ouch!