Here is what is happening. Whenever we vacuum the pool the return line (the one going back to the pool) almost stops flowing after about 3 minutes of vacuuming. We then backwash and rinse and the flow returns to normal.

We have had the pool for about 5-7 yrs. Do we need to change the sand? If so, can I take off the valve assembly while the hoses are still attached and water in the pool?

Please help!

THANKS!
Lloyd