2001/2002 Hot tub filter housing broken

[Shawnharned2]

Hi guys, been a long time pool school member here. And have learned a lot.
I recently bought a used hot tub from a client because he upgraded his due to the old one having a cracked water filter base/housing.
My problem is I’ve had one spa repair guy come and and couldn’t do anything because they didn’t sell this type of filter base anymore because it has three outlets...Unlike how the new ones have two.
my question is why can’t I just cut this old one out and install a new filter housing that has similar dimensions at the top that is roughly 6inches and plumb two of the outlets into one? I’ve done sprinkler & pool plumbing but not hot tub before. The hot tub is a Renew Image 631 Blue Acrylic - IMSB63100.

if anyone has any comments or questions please reach out. I will attach pictures etc, If I’m in the wrong thread just transfer it over.

 

[ajw22]

Let’s see what @RDspaguy says.

 

[RDspaguy]

If I am seeing this correctly,, the filter canister is a suction side filter with a line to the skimmer and another to a main drain in the footwell, then on to the pump with the third. I assume it had some cap or lid on the top of the filter can?
There will be a spring check valve inside to force skimmer action but allow flow from the main drain as the skimmer fills and clogs. I would plumb a spring valve to the main drain pipe, then tee that into the new can along with the skimmer pipe. Pay attention to flow direction of the can, and spring valve for that matter, if you plumb it backwards it will not work.