How to glue in 12" of pipe and fittings into 9"

Can someone point me to a tutorial on how to glue in a, well in this case a Jandy energy filter, into the middle of piping. Between the filter/fitting/pipe I have 12" of stuff that needs to fit in 9" of space. Obviously 1 1/2" of pipe fits into each end.
How is this done?
Unfortunately I'm a handyman by necessity and I dont have much experience at this. The system I'm working with is like 20 years old so its quite brittle. Kinda scared to just manhandle it and end up cracking the pipe. The whole system is encased in concrete at the base so cracking anything would be a nightmare.

Ive looked and looked on Youtube but havent really found a video for this trick of the trade.