Clean your filter with Muriatic acid. You have been cleaning your hot tub filter regularly with hose and water, but it is still not coming clean. Well, you can use muriatic acid to clean your filter, but please remember that muriatic acid is very corrosive and needs to be handled with care.
Spray carefully with a high pressure hose nozzle to remove debris from each pleat. Soak the cartridge for 8 hours in TSP solution (1 cup TSP per 5 gallons hot water). Rinse clean. Soak the cartridge 1 hour in an acid solution (1 cup acid per 1 gallon cool water).
Spa manufacturers recommend cleaning the filter regularly — as often as every two. spa. Always wear gloves and eye protection when handling muriatic acid.
For spa owners with hard water, calcium deposits may restrict filter cartridge flow. After cleaning the filters, remove calcium scale by soaking in a 20 parts water, 1 part Acid Magic solution just until bubbling stops. Acid Magic is safer than muriatic acid, but just as effective.
filled it with water (and the cleaner) and let them soak overnight.. same kind of cartridge filter that I could use muriatic acid to clean the filters by. What I DO know from living with cartridge filters in a pool, portable hot tub, and .