The pool pump is a motor that provides constant pressure by providing suction power through the skimmer, where the water is filtered and then released through the pool's return jet. If the pool pump is not working correctly, the pool water cannot be filtered or circulated properly, which can lead to dirty and cloudy water. Fortunately there are several warning signs prior to the motor burning out that can help you determine if something is wrong with the pump. Most of the time, you can still use the other filter components by connecting a new motor.
Monitor the filter pressure. There is a gauge located on the side of the filter that measures the pool's water pressure. This number should be consistently between 12 and 17 pounds of pressure per square inch, or psi. When the pressure falls below 12 psi, it doesn't necessarily mean the pump is bad.
Back-wash the filter to clean it of excess dirt and debris that could be lowering the filter pressure in the pool. By back-washing the pool, you can eliminate the filter as a cause of concern for the lower-than-normal pressure. Low pressure is usually the first sign of a bad filter pump. Turn the filter off to back-wash, and turn the release valve at the bottom of the filter. Drain the water from the release valve until it turns clear, then shut it off. Pump the handle three times on the filter, and restart. Do not add any earth to the filter. Normally you'd add new earth, but for the purpose of monitoring the pressure do not add any earth.
Turn the filter off again, and clean the skimmer basket, both that of the pool and that of the small canister-type part of the pump that is connected by a hose to the pool skimmer. Turn the canister-looking pump open. Water will rush out from the pump, but this is normal. Just empty the basket quickly and replace the top. This basket can sometimes get clogged from vacuuming the pool.
Monitor the pressure again after back-washing, pumping the filter and cleaning the skimmer baskets. If the pressure continues to fall in less than a few hours, it's likely the pump is not functioning properly. It could be that you need to clean or lubricate the motor. Take it to a pool professional to evaluate the motor if the pressure continues to decrease. Pool pressure is supposed to hold steady until the earth in the filter get dirty by collecting an excessive amount of dirt and debris, which usually takes about a week. That's why back-washing is pivotal to pool maintenance because it restores filter pressure. However if the pressure is dropping as soon as it's back-washed, there is a problem with the motor.