I cleaned mine outside.
Get yourself a bowl or somthing, and somthing to scoop the sand with.
And a garden hose with sprayer attacment.
Fill the bowl about halfway full of sand, and use the sprayer to mix the sand up.
I stuck the sprayer partially down in the sand and moved it around in circles.
Dump of excess water...Repeat untill the water on top of the sand is clear within a couple of seconds.
Its really time consuming. I cleaned 150 lbs in about 4 hours.
However when I dumped the sand in my tank it cleared fast.
Hope I've helped.
-ttldnial