My pool is a 17K gallon AG with vinyl liner. It has a sand filter. I have been maintaining an above ground pool since about 1995. My water is Crystal Clear. I do not use an SWG. Around 3+ years ago, my pool started developing rust-colored deposits on the bottom of the pool. If you run a brush across them, they will dissipate into the water. Some of them are hard to get up and you have to scrub over them with the vacuum and will leave a dark spot where the deposit was. A few spots have started to leave a little of the rust color even after running the vacuum. Over time, the bottom of the pool liner has developed numerous dark spots where these deposits always show up. The area that is most affected is the half of the pool that is closest to the skimmer and return jet. I have always taken water samples to my local pool dealer for analysis. I have changed the sand in the filter each year for the past 2 seasons. This year I replaced the laterals as well. After running the vacuum I always backwash thoroughly before turning the pump on to circulate. If I leave the pump off, the deposits will not start to show up until about 2 to 3 hours later and they are very small in size and number. After turning on the pump, within 15 to 30 minutes, I can see evidence of the deposits reforming again in force. If I vacuum to waste, I get the same result. I have treated for green, mustard, and black algae, multiple times using Banish, Spot Kill, and Yellow Treat. After each treatment, I would never introduce anything back into the pool until I knew if the deposits were coming back or not. They always come back. My local pool dealer finally agreed to send a water sample (both pool and make-up water) to BG for analysis. I was able to capture a good amount of the deposit matter and include it in the pool sample. The analysis report stated that I basically had DIRT and other debris in my pool. The mystery is that no-one can tell me where it's coming from. I am posting Pictures, http://s1214.photobucket.com/albums/cc498/mljpool/and a copy of the analysis report. The most recent analysis I have from my local dealer is as follows:
Please help if you can.