This product is a marvel. We switched from Aquafinesse, which was an impressive improvement from bromine. To find a product we like much more than that one is amazing. We left our hot tub for 4 weeks with Spa Marvel in it that had been added 2 months before we left. We turned the temp down a bit and added 2 extra chlorine pucks. On our return home the hot tub was the same as we left it. We turned it up, added a chlorine puck and were in it the next day. Thank you for this incredible product.