When I change pump speeds from low to high, dirty water comes out the 2 main return jets for a few seconds. The dirty water is light brown or sandy colored and dissipates quickly. This is after the pump has been running on low speed for a while. I have a newly installed Pentair Superflo 2pseed pump and a Hayward sand filter. The filter sand was replaced last year and has been backwashed within the last week. Any thoughts would be appreciated.