I have about a 30,000 gallon pool with a Hayward Pump and DE Filter. The pump is 2.5HP and 230 Volts. This is my third year at my new house and this pool and I've noticed that the returns always lose pressure after about 4 hours of runtime. I don't notice any leaks around the pumping station. How do I know when it is time to purchase a pump? Is there anything I can spot check before settling on purchasing a new pump?