Drop-in tablets sit in your tank bleaching everything around them and never touch the actual problem. The brown ring and the white scale collar at the waterline are mineral deposits — calcium carbonate and iron — and bleach does not dissolve minerals. Acid does.

This is a 35% citric acid concentrate you pour in, let dwell for 30 minutes, and flush. No chlorine, no blue dye, no fumes when you lift the lid, and nothing sitting against your flapper and seals around the clock. One 16 fl oz bottle holds 8 full-tank doses.

Features:

• 8 uses per bottle – One 16 fl oz bottle delivers 8 full-tank cleaning doses at the standard 2 fl oz dose — a two-year supply at quarterly use.
• Removes what bleach cannot – 35% citric acid dissolves calcium carbonate and chelates iron deposits, lifting the brown ring and white scale collar at the waterline.
• Bleach-free, no blue dye, no fumes – Zero chlorine and zero colorants. Nothing stains grout, and there is no chemical smell when you open the lid.
• Safe for rubber components – A 30-minute contact time followed by a full flush, instead of the continuous chemical exposure a drop-in tablet creates.
• Septic safe and biodegradable – No hydrochloric acid and no harsh oxidizers. Every ingredient is biodegradable and safe for standard septic systems. Packaged in the USA.

How to use:

1. Shut the tank supply valve.
2. Pour in 2 fl oz of concentrate.
3. Let it dwell for 30 minutes.
4. Reopen the valve and flush three times.

Why Think Crucial:

• US-based, family-owned brand serving over 1,000,000 households since 2007
• Replacement parts, filters and cleaning solutions for commonly used appliances
• Customer support available if a product does not perform as described