My problem was hard white foam which appeared after a heavy rain washed a tremendous amount of debris into my pool from the huge pine tree which towers over it. This followed a long period of bad air caused by firestorms in California last year. I laboriously filtered the water and adjusted all the chemicals, so that the water (which was green immediately after the rain) became perfectly clear and odor-free, but the foam was visible whenever I heated the spa. I would remove it with a net about 1-foot square and pile it next to the spa. I could easily remove 50 square feet (50 netfuls) of this hard white foam each time I used the spa. It would form huge piles on the ground that bounced each time I added another netful of foam, much like pudding. The next day I would see green residue on the ground where the foam had been. I was not worried that the foam could be dangerous to my health, but I didn't like it very much. From what I could determine on the internet, the foam was caused by organic matter that had gotten into the water and was too small to be removed by my cartridge filter. I could have kept removing the foam manually repeatedly, but the volume of water in the spa is very small compared to the volume of the pool, and it would have taken forever to remove all of the foam in this way. I had read that Maintain flocculant should not be used with a cartridge filter, but my cartridges were about 9 months old, and I didn't mind sacrificing them. First I took out the cartridges and washed them. There was a lot of green debris on the ground afterwards but nothing out of the ordinary compared to previous washes of other cartridges. Then I replaced the cartridges and set up the pool vacuum. After getting the air out of the system, I turned off the pump. I made sure that the pH was above 7.8 and added 1/2 bottle of this Maintain flocculant, spreading it over the top of the pool. The next day I noticed that there was a lot of white powder on the bottom of the pool, but the water was still cloudy and there was also a lot of powder adhering to the walls of the pool. So I brushed the walls, which caused a dramatic increase in water cloudiness, and waited another full day before vacuuming. On the second day, the water was clear enough so that I could see the bottom well enough to vacuum and there was relatively little flocculent adhering to the walls. I turned on the pump and quickly removed the cap from the opening at the bottom of the cartridge filter. This of course caused a huge amount of water to spill onto the ground around my pool equipment. Then I rushed over and started vacuuming the pool. When the vacuuming was complete, I quickly turned off the pump and replaced the cap. Then I refilled the pool with tap water. The pH dropped to about 7.4. I filtered the water in the pool to remove the cloudiness. The next time I turned on the spa, the foam problem was greatly reduced but not eliminated. I could still remove about 10 netfuls of foam each time I heated the spa. So I washed the cartridge filters again, but this time they seemed quite clean, and there was very little white material on them, suggesting that they had not been affected by the flocculent which had been able to escape easily through the bottom of the filter. Since I still wasn't satisfied, I added the other half of the bottle of Maintain flocculant and repeated the above procedure. This time, I achieved a further reduction of foam, to about 5 netfuls each time I used the spa, but the difference was not as dramatic as the first time. In retrospect, I should have used the entire the bottle of flocculant the first time. Finally, after filtering the pool thoroughly with the old filter cartridges in place, I replaced them with new ones. In conclusion, I was able to prove that it's OK to use flocculant with a filter cartridge, as long as you're willing to replace your cartridges, and it seems to me that replacing the cartridges might have been unnecessary, since they did not appear to be very much affected when I cleaned them after the floc treatment. I also demonstrated that flocculant can greatly reduce, but not eliminate, the hard foam problem that I've been experiencing.
