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Toilet tank mildew problem
Hi all:

I am trying to find a solution for a mildew problem. Over half of 350 or so toilet tanks in a multi-family development I inspected have mildew growing in the tanks (tested and confirmed by an environmental company).

Does anyone have any ideas on what could be causing this? You pull up the lid and the entire inside is covered in black you can't even see the parts. I believe that Clorox tabs may be one solution but since I've never seen this before and this property is in a state where there is very little humidity, I am looking for some feedback. Thanks!
Posts: 1 | Registered: 31 October 2006Reply With QuoteReport This Post
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I recently experienced the same problem in one of my bathrooms because now it is just my wife and I and this upstairs bathroom does not get used often. I do live in a high humidity area, Texas Gulf coast, but I poured a cup of bleach in the tank and it appears to have solve the problem. I will be using the bleach tablets that you drop in the tank to eliminate future mold build up.
Posts: 1 | Location: Houston, Texas | Registered: 06 November 2006Reply With QuoteReport This Post
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I live in Phoenix, Arizona and even with hardly any humidity, that is still a constant problem for us. We've tried clorox and other tabs. Doesn't seem to eliminate the problem.
Posts: 1 | Location: Phoenix, AZ | Registered: 06 November 2006Reply With QuoteReport This Post
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I live in Arizona and don't really have a mildew problem but I do know that putting chlorine in the tank will destroy the brass tank bolts and eventually cause a flood.
Posts: 1 | Registered: 06 November 2006Reply With QuoteReport This Post
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If you use bleach, do it for a one time use weekly, it also cleans out the little holes under the rim of the commode. If you use the tablets, it will cause all the brass parts to severely corrode and fail.

Posts: 2 | Registered: 28 December 2005Reply With QuoteReport This Post
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I would like to know what causes it. Does the water need to be tested? Could the culprit be bad water? I'd like to know also. I live in high humidity TN. It continues to be a problem here. Getting rid of it isn't the problem to me. What causes it is.
Posts: 4 | Registered: 26 January 2006Reply With QuoteReport This Post
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No Dawn the water does not need to be tested.
To understand why you have mold you need to know how it grows.
1st. you need a food source, oxygen and moisture.
We know the moisture source and oxygen source, both we cannot control in this issue. However the food source can be altered. IN normal mold removal we control the moisture as that is usually the only thing we can alter both in prevention and cleanup. But in this case we need the water to flush the toilet and we have no way to remove the oxygen in the water and air.
The food source is what is allowing the mold or Mildew to develop. Which is the only thing we can alter. To clear this up the inside of each suspect tank would need to be emptied and cleaned very well. Once done the regular use of these toilet tabs will aid in future prevention. An occasional flush will help as well. Standing water will allow for this issue to develop. Think of it like a swimming pool with the filter off for a long period of time. What happens? A green or black film develops on the walls and floor. Simply shocking the pool with chemicals may clean it up but it take a long time. But if we vacuum it or drain the water and clean the liner when we fill it up it does not develop until we forget the chemicals and to turn the filter on. Heat also plays a big factor in development, if the apartments are not cooled and get warm during the summer this increases the development of mildew or mold growth. Hope this clears things up.
Posts: 1933 | Location: New Jersey | Registered: 31 January 2006Reply With QuoteReport This Post
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Because the mildew occurs in the tank and from other responses and bleach seems to only be a temporary solution. My concern is how the mildew is getting in the tank. I would look at your water source (well) or holding tank. (I believe your problem stems from your water source because others are experiencing the same problems.) A possible solution is adding bleach to the water source before going to bed, and allowing the water to run clean in the morning by turning on all your taps until the smell of bleach is gone. Of course, it you are on a multi-system well (which it sounds like you are), you would need to get permission from everyone on the well, and talk to the person in charge of the well maintenance. I would also have your tap/drinking water tested. If the mildew is coming from your water source or holding tank, chances are the mildew is also in your drinking water/taps.
Posts: 1 | Location: Connecticut | Registered: 07 November 2006Reply With QuoteReport This Post
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According to mold remediation experts. Chlorine bleach only masks the mold by bleaching it. It is stillthere because the source is still there. I would contact an expert.
Posts: 1 | Registered: 13 November 2006Reply With QuoteReport This Post
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First, technically, mildew is a misnomer. Mildew is a mold that grows on the surfaces of leaves of living plants. What you have is mold growing inside your toilet. Second, most mold issues are blown out of proportion by our ambitious news media. Mold is one of the oldest forms of life. Mold or mold spores are present everywhere on the face of the earth including Antarctica. Unless you are living in a clean room environment, the last breath you took included more than a few mold spores. Those persons who have serious issues with mold are cancer patients, transplant patients and anyone else with a compromised immune system. Those people are mostly affected by Aspirgillus molds. There are people who are sensitive to allergens associated with the chemicals produced as a result of mold's digestion of food sources, as well as some of the components of mold itself. A ten percent bleach solution will kill mold and mold spores and is the most common method of removing mold in healthcare settings. Be cautious of germicides, pesticides or herbicides as a mold correction. Mold is a fungi, not a bacteria or a virus. Also, while any of the "cides" may kill mold, it is only thorough cleaning which will remove mold spores and help to prevent a re-occurance. Killing mold without a clean up also allows the mold "corpse" to remain which is a suspected allergen to some people. Mold requires moisture, temperature and a food source to survive. What oxygen it needs, it can obtain readily through moisture or that trapped within substrates of material it lives on. Mold will eat organic materials such as wood or paper. It will not eat minerals or metals. It will however, live on the dirt accumulated on those surfaces. Construction dust is a prime food source for mold as it generally includes plenty of organics. If you have thoroughly cleaned your toilet tank and the problem re-occurs, then I would look at having a water sample tested. What you have may not be mold, but a bacteria in the water itself. Certain waterbourne bacterias while they may not be harmful to a normally healthy individual, can produce a black waste residue which imitates mold. Lastly, be very careful before allowing someone who claims to be a mold remediation "expert" apply any kind of "mold killing product" in your home. The cure may be more of a hazard than the disease. I have just finished 2 days at a seminar that included mold remediation in healthcare industries as well as an annual refresher on mold remediation, supervisor level. I can attest that there is a lot of mis-information out there, and a lot of arm chair experts. To date only one state (Texas), has any kind of requirements for mold remediation proffesionals, so "experts" are hard to come by.
Posts: 245 | Location: Annville, PA | Registered: 03 July 2006Reply With QuoteReport This Post
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we here often suffer from algae in our tanks, it comes from cyanobacteria. we use something called chemiclean to get rid of it, or live animals which of course aren't appropriate for a water supply, and some people, if their rock isn't live, use boiling water to scorch the sucker out. we don't have the luxury of using bleach. i did however hear that the white clorox tablets work better than the bluing ones
Posts: 20 | Registered: 16 June 2008Reply With QuoteReport This Post
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This sounds like a humidity problem.... I will look into this...

I have to be honest I never ran into a problem like this. But in most cases your humidity levels are a bit high.

My suggestions, clean up the toilet but measure your humidity to make sure it is normal levels.

Have a mold problem? You do not need certification to get it done yourself, free helpful advice on doing your own mold remediation at
Posts: 6 | Location: Fort Lauderdale, Fl | Registered: 13 November 2008Reply With QuoteReport This Post
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