I am new to pool ownership. My 18x36 vinyl liner pool was built in 1987. 3ft shallow and 8ft deep end (25-000 -26,730 gallons?). I just opened the pool back up from a 2 year break. I remember having a hard time balancing chemicals last time it was open, and I noticed vacuuming through the skimmer took forever and suction was not great, so I started questioning the pump size and filter size. Currently I have a Hayward SP2605X7 with a 3/4hp motor, and a hayward c751 cartridge filter which I think is undersized based on online research. All the plumbing is 1.5" pipe. It does not have a main drain, so only one drain line from the skimmer which is about 125ft from the pump with approximately 4-90 degree elbows and 1-45. There are 4 return lines. One jet/return about 2' deep in the deep end, one jet in the shallow end opposite side of the pool from the one on the deep end, and 2 jets in the steps. I saw from research that a 1.5 hp pump and and a 300-400sqft filter was recommended. The only problem is that I have only one intake line, not 2. With only having one intake, what would you suggest? If it is the 1 or 1.5hp system, can I just change the motor on my system? Thanks in advance for your advice and help. Mike Jones