Desperately need help with my pool!

[Lady Neysa]

Please help!  My pool is driving me crazy!  Its an above ground pool with sand filter. The sand was replaced this year.  When I try to vacuum it blows the dirt right back into the pool.  We had this same problem last year and as a result barely got to use our pool.We were told to check the "spoke tube" things, or whatever theyre called at the bottom of the filter, to check for cracks or  breaks.  We did that when we put in the new sand and as far as we can tell everything is ok. 

The only other thing we can think of is that the top valve where you switch from filter to backwash, rinse, etc. is bad.  It works fine on normal filter mode.  Any other trouble shooting suggestions?  If you need a model #  etc..  I'll get it for you.