poolownerIII

I have a fulflo cartirdge filter and have had to replace the cartidge element twice (so far) because the top portion has collapsed or has broken. The filter is rated for a 1HP pump and I am using a 1 HP pump. Water flow through the system seems fine and the system is running at 7 PSI. I have no idea what is going on and other than the fact that the filter element has broken it cleans the pool nicely. Any thoughts?