These filters are pressurized bombs. They are made out of fiberglass reinforced polypropolene. Trying to make a repair could be very dangerous, and I obviously dont recommend it.
How old is it?
Is it the top or the bottom?
Is it a Clean and Clear, or a CNC plus?
What size is it?
Have you ever replaced the cartridges?

CNC plus , 5 years old, never replaced the cartridges (clean 3 times a year), i think it is the bottom, size=420? Will have to check those last two when i get home.

Yes it is the bottom and it is a 420.

Too bad its the bottom, I had a bottom split a couple of months ago, and would have given you the top.
The part number you need is 178578. Run between $250, and 300.
But since you have never replaced your cartridges you should probably buy a complete new one for around $600.00. This will save you money in the long run.

check the warranty on this, it may be up to 10 years.

I was thinking just that just-a-pb. That if i were to also get new cartridges might as well get a complete new unit.
Racket: I talked to someone last night who also thought it may have a 10 warranty.