my berkey lower chamber is getting a pink or slimy film on the inside walls, what is this and how do i clean and prevent it?

Diagnosis

The pink or slimy film appearing on the interior walls of your Berkey Royal lower chamber is almost certainly a colony of Serratia marcescens. This is a common airborne bacterium that produces a reddish-pink pigment. Contrary to popular belief, this is not a failure of the Black Redox filters; the filters remove contaminants from the water passing through them, but they cannot prevent bacteria from landing on the stainless steel surfaces of the lower chamber from the air every time you open the lid. This growth thrives in the high-moisture, low-oxygen environment of the lower chamber, particularly along the "water line" where the surface of the water meets the steel. If the film feels slippery or slimy, it has developed into a biofilm, which is a protective layer the bacteria create to shield themselves. You can confirm this by noticing the film is most prevalent near the top rim of the lower chamber or around the spigot assembly, where water may linger or splash during refills.

How to Fix It

To completely eradicate the biofilm and sterilize the Royal system, follow these precise steps:

1. Drain the lower chamber completely by opening the spigot. Remove the upper chamber and lift out the Black Redox filters. Set the filters aside in a clean bowl of filtered water; do not let them dry out or touch the bleach solution.
2. Prepare a sanitizing solution using 1 tablespoon of unscented, liquid household bleach (5.25%–8.25% sodium hypochlorite) per one gallon of warm water. Do not use scented or "color-safe" bleaches.
3. Fill the lower chamber with the bleach solution. Use a soft nylon scrub brush or a clean microfiber cloth to vigorously scrub the interior walls, focusing on the waterline and the interior corners.
4. Remove the spigot by unscrewing the plastic nut from the underside of the chamber. Scrub the interior of the spigot hole and the spigot itself using the bleach solution.
5. Soak the upper chamber and the lid in the bleach solution for 10 minutes. Scrub the interior walls of the upper chamber, specifically the area where the filters sit, as biofilm can migrate upward.
6. Rinse all stainless steel components thoroughly with hot, filtered water until there is no remaining scent of chlorine.
7. Reassemble the system: Reinstall the spigot, place the filters back into the upper chamber, and refill with fresh water.

If That Didn't Work

• Vinegar and Baking Soda Paste: If the pink stain persists after bleaching, it may be a mineral deposit that has trapped the bacteria. Create a thick paste of baking soda and white distilled vinegar. Apply it to the stained areas, let it sit for 15 minutes, and scrub with a non-abrasive scouring pad.
• Hydrogen Peroxide Treatment: For stubborn biofilms, use 3% hydrogen peroxide. Pour it directly onto the affected areas of the dry lower chamber, let it bubble for 5 minutes, and scrub. This is often more effective at penetrating the biofilm layer than bleach.
• Spigot Replacement: If the slime is originating from inside the spigot and cannot be scrubbed away, replace the spigot entirely. Over time, the plastic seals can harbor bacteria that are unreachable by brushes.
• Deep Sterilization Cycle: Fill the lower chamber with a mixture of 1 part white vinegar to 4 parts water and let it sit for two hours before the final rinse. This alters the pH of the surface, making it less hospitable for Serratia marcescens to return.

Heads Up

• Filter Protection: Never allow bleach or cleaning chemicals to touch the Black Redox filter elements. This will chemically strip the filtration medium and render the filter useless.
• Avoid Abrasives: Never use steel wool or harsh scouring powders on the 304-grade stainless steel. This creates microscopic scratches that provide "homes" for bacteria to hide and grow, making future outbreaks more frequent.
• Airflow Management: Keep the lid closed at all times. The pink film is airborne; minimizing the time the chamber is open reduces the number of bacteria entering the system.
• Rotation Schedule: Implement a "deep clean" every 30 to 60 days, even if no visible film is present, to prevent the biofilm from establishing a permanent foothold.