Pressure going from 15 psi to 25 after vacuming for 5 min. ??

If you have dirty water returning from your returns then more then likely you have a cracked filter manifold or a tear in the filters also how much dirty are you vacuuming each time sounds like you may need to replace your filter elements
 
My experience, with both Pentair and Hayward sand filters, is that vacuuming an extremely dirty pool can result in dirt bypassing the sand. Very frequent backwashing may be required.
 
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