help me with my build of new tank

[savethereef]

Hey guys as some of you know i am building a new 180. I already got a hole saw today to drill my acrylic sump. But some of the PVC i am doing i need some cement to glue it together. I just came from home depot and they had different weldon PVC cement. i saw the primer which is the purple stuff then i saw the cement but they had different numbers on them which one do i use. And how do i primer everthing 1st with purple one then the cement or no need for the purple one. Please help me. well i am talking off going out hopefully someone can give me a couple answers so when i come back i can buy the correct one. Ill take some pics of my progress also thanks guys