Leaks at your pool pump are a pesky problem. You have to constantly add water to offset the leak, which can become costly, and throw off the pool's pH balance ... causing you to add more and more chemicals to maintain the pool.
The most common cause of leaks at the pump are from threaded fittings. Over time schedule 40 pvc will shrink, letting water escape and start a drip. A leaky pump can destroy your motor & cause your pump to lose prime and overheat.
While there is no definite way to prevent this from happening, there are some precautions you can take upon installation. One way is to use a CPVC schedule 80 nipple on both the suction and discharge of the pump. If you get one of the 12" double-sided nipples then one is all you will need.
First you will want to wrap both threaded ends of your nipple with teflon tape or liquid teflon known as "pipe dope."
Next, thread one end into the suction part of your pump. Line the pump up to where you will connect it to the suction header, take your measurement, and saw off the remainder of the nipple being sure to leave enough for your discharge side. Then thread the remaining piece into the discharge of the pump. (If your plumbing is 1 1/2" and your pump threading is 2' you will have to use a reducer bushing in order to plumb up.)
Another step you can take to insure future repairs can be made easier, is to connect up to your suction header and filter intake with a union. This will allow you to easily disconnect the pump at anytime, and keep you from running out of pipe to coupling onto if you have to make multiple repairs over time. While this is only one way to remedy the leak problem, I have found it thru experience to be the best option yet for prevention.
Always read your owners manual and take precautions for safety. Also be sure to shut the breaker off to your pump before attempting any repairs.