Grease can clog any drain line connected to a septic system or city sewer line. Mix the grease with lots of soap and hot water for a minute. This will emulsify the grease and prevent clogs. To prevent other clogs, drain and water lines need periodic maintenance for good drainage.
Water pressure drop is based on what is happening in your home. Two plumbing fixtures can cause reduced water flow. Plumbers can use larger pipe as main feeder pipe.
Copper pipes can corrode due to aggressive water, chemicals and poor workmanship by your plumber. The plumber may leave excess flux on pipes and pipe fittings.
Water pressure causes noise problems. Water hammer is due to water pressure against faucets, valves or sidewalls of pipes. Solve it with larger piping.
Low water pressure problems can be checked easily. Water shut off valves need to be checked indoors and out. Your local water works people can do a bypass check.