Most users of whole house water filters replace and throw them away every few weeks or months, depending on household water consumption and how rusty and contaminated their incoming water is. While filters aren’t expensive, there’s an effective alternative to tossing them out: cleaning and reusing the cartridges.
Clean Filters With Muriatic Acid
Many municipalities that supply public water clean their large rust and sediment filters with hydrochloric acid (HCl), better known as muriatic acid. It’s difficult and prohibitively expensive for municipal water providers and industrial plants to replace their filter media when they became rust laden—especially in regions with high iron (rust) content where fouling is a persistent problem. Muriatic is a powerful acid that dissolves rust and hard water calcium deposits effectively without harming most cloth and paper filters. Many swimming pool owners are familiar with muriatic, which is used to adjust pool water pH.
Here’s What You’ll Need to Clean Filters:
- Two plastic pails or buckets
- Muriatic acid (a gallon—enough to last an average household a year—costs about $4.00)
- Protective clothing, gloves and eye wear
- Baking soda
Filter Cleaning Procedure
Pour about half a gallon of water into a plastic pail or similar container wide enough to hold the cartridge when laid down horizontally. Obtain muriatic acid from a hardware, home improvement or pool supply store. Add one or two cups (8 – 16 oz.) of acid to the water (never pour water into acid), preferably outside or in a well-ventilated area. Muriatic is hazardous, so take the same precautions as swimming pool owners routinely do: wear eye protection and clothing that covers exposed skin areas, and gauntlet-style acid-resistant gloves. Don’t breathe the vapors.
Remove a dirty filter cartridge from its housing and wash off as much of the rust and debris as possible, preferably with a high-pressure nozzle. Then immerse the cartridge in the bucket of acid and leave it to soak in a safe place, away from children or pets. Within a week or less the acid solution will completely dissolve the rust, and the filter will be as clean as new. Carefully remove the filter from the acid bucket, drain and immerse in clean water in a separate bucket. Do a final rinse in running water. Empty the rinse bucket water into the acid bucket and save it for cleaning future dirty filters.
Neutralizing and Disposing of Spent Muriatic Acid
It’s environmentally irresponsible and probably illegal to dump acid down the drain, into a municipal or septic waste treatment system, or in the trash. The good news is that most of the acidity (and thus effectiveness) of the muriatic cleaning solution will be spent, i.e., neutralized by the chemical reaction of dissolving rust from filter cartridges.
Nevertheless, neutralize the spent muriatic before disposing of it. Mix a cup or so of baking soda with a gallon of water in the spare bucket. Carefully pour in the used muriatic and stir. It’s safe to pour the neutralized liquid (harmless sodium carbonate) down the drain when fizzing ceases. Alternatively, take it to a hazardous waste recycling facility.
Filters cleaned this way should last five to ten years—perhaps longer.