Toilet bowl cleaner tablets that sit in the bottom of the tank have two advantages over the older type that hang of the side of the bowl: they are easy to install without having to touch the toilet bowl and not visible when in place. But, because they dispense a disinfectant chemical into the tank instead of the bowl, the flush mechanism is exposed to the chemicals, which often includes chlorine bleach.

    Toilet manufacturers noticed an immediate surge in leakage complaints for their products after the drop-in tablets were introduced in the early  1990s. One of the problems the manufacturers discovered with the new product was that if a homeowner left on vacation or, even worse, installed the tablets in a seasonal home, the concentration of the chemicals would intensify in the tank to corrosive levels as the tablet slowly dissolved without any toilet flushes to dilute it.

    The Clorox Company responded to a class action suit claiming damage to toilet mechanisms, even though the manufacturer claimed that their Clorox Automatic Toilet Bowl Cleaner “does not damage toilets,” with an $8-million settlement. Clorox denied any wrongdoing, but has since added the statement “tablets should be used in toilets that are flushed daily” to the product packaging. Unfortunately, it is not practical for a consumer to fish the tablet out of the bottom of the tank before leaving home for an extended period.

    When a cleaning tablet is left to dissolve completely without any flushes, the water in the tank becomes intensely blue and chlorinated. Here’s an example we saw recently in a house that had been for sale and empty for several months.

    Toilet manufacturers responded to the problem by adding stickers to the inside of their toilet tanks, like the one shown below by Kohler, as a consumer warning that “use of in-tank cleaning products voids warranty, as they can destroy parts and cause water leaks that may lead to property damage.”

    Plumbers also recommend not using the tablets based on their experience replacing deteriorated plastic, metal and rubber flush mechanism parts—especially the flapper. 

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Here’s links to a collection of our other blog posts about “TOILETS”: 

• Why is there sand in the bottom of my toilet tank?  

• Why is there mold inside my toilet tank?    

• What are the pros and cons of a wall-mounted toilet?

• What are the minimum clearances around a toilet? 

• What is the little tank on top of the water heater for? 

• What is that big thing in the toilet tank? 

• What is the white plastic tank inside my toilet tank?

• Can I install a commercial (wall-mounted flushometer) toilet in my home? 

• Does a home inspector check toilets?

• What is the code required minimum height above a toilet? 

    Visit our PLUMBING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.