Have a 2 yr old salt pool - jandy equipment. White chalky substance was settling in bottom of pool by every return port. Thought it was sand returning to pool so replaced the cartridge filters (only 2 yrs old) but that did not solve the problem. Finally called a pool tech - he came out and said it was due to having calcium buildup in the saltcell. He cleaned the cell with muratic acid/water solution and then realized that the sensor was bad. Replaced the salt sensor in late June of 2010. All was great for about 1 month, then white chalky substance was back again. I took cell out and soaked in muratic acid solution until clean, but this did not fix the problem- still have all that stuff in the pool - it isn't sand because it feels like a powder and cartridges are new. And now I can no longer get a reading on my handheld PDA of the salt concentration in my pool (which is also what happened last time when we discovered the sensor was bad). Any suggestions? I am out of ideas. Thanks