Help with Pentair 320 plumbing

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I have a Pentair 320 with an inlet and external outflow pipes currently im using 2 1/4 plumbing however the pentair uses 2 3/4 inflow and exflow so I have to convert the pipes. Now I believe Pentair had a kit model number 271096 and 170036 to convert everthing. Problem is my installer used rotten flex tubing to connect the pump to the filter so its leaking and of course he used glue so I have to cut it out and replace it to stop the leaks. If you want to see the plumbing see the link below.

http://www.saradec.com/part/data/79part.htm

Item number 16 and 17 are the operative plumbing. They are salty about $50 for the 16 and $100 for the 17 does anyone know of a generic supplier? I mean common its plastic pipes yeah sure its using a quick disconnect but so what shouldnt cost more than a couple of bucks. Both the inlet and export use 2 3/4 screw in male fittings I have to convert it to 2 1/4 for my hayward pump output and the return for my pool uses 2 1/4. Any ideas anyone know of a place selling generic pipe parts that will do the job?