How To Test For Mold In Water + Water Mold Facts

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Can mold grow in water? Interesting question. We all know that mold needs water or another moisture source to grow but can it actually grow in water itself?

A lot of people would assume that yes it can. Why? Because if you have ever owned a reusable water bottle, you likely have had to clean mold in the water bottle. But was it the water itself that grew mold or something else?

What about white water mold? Swimming pool mold? Mold in water pipes? Is that actually mold growing in water?

Today I am going to tackle the subject of water mold as well as how to test for mold in water. Let’s get started shall we?

A petri dish with a dropper pipette dropping a drop of water into the test. Testing for water mold.

Can Water Grow Mold?

Mold can grow in water if the water is rich in nutrients. The mold will form a mat on the surface of the water and produce spores. If the water contains little or no nutrients, then the initial growth would die for lack of nutrients.

Water can only grow mold when it is at rest. Moving water can carry spores but it cannot “grow” mold while in motion. A pond with little movement is more likely to grow water than a river which is constantly in motion. Water in a well or at a water treatment plant is more likely to grow mold since it can remain stagnant for a while.

How Does Mold Get Into My Water Supply?

  • If your water source comes from a well, then you might be at risk for mold in your water if your well cap is damaged or is not adequately sealed.
  • If your system has high levels of oxygen and an organic food source (this could be something as simple as a paper filter cartridge), mold has the ability to survive in your water.
  • You may have mold growth in your water softener, water purifier, or water storage tank.
  • Your faucet aerator (the screen assembly) might have mold growth.

How Does Mold Grow In Water Pipes?

It is rather difficult for mold to grow in water pipes. Water pipes don’t have adequate oxygen or food for mold to grow significantly, but they do have a moist, dark environment that allows mold to form under the right circumstances.

Mineral build up in your pipes would provide a food source. A tree root that infiltrates your pipes can provide food for mold. If you have tiny holes in your pipes (copper pipes are especially prone to developing microscopic holes) then dirt and other particles can get inside your water pipes allowing mold to grow.   

Signs You Have Mold In Water Pipes

  • If you inspect inside an accessible water pipe and see mold, then your entire water line might have a mold problem. Don’t confuse calcium build up with mold. Calcium build up is hard and doesn’t easily come off if you rub it with your finger. Mold will rub right onto your finger.
  • You smell a moldy or musty smell when you run your water.
  • You notice a gritty, dirt like substance at the bottom and sides of your toilet.
  • You see an abnormal amount of mold in your shower, bathtub or toilet AND it grows back very quickly after removal.
  • Mold is growing in other locations around your home.

How To Remove Mold In Water Pipes

This is a bit tricky and in my personal experience there is no hard and firm, 100% guaranteed way to accomplish this short of replacing your entire plumbing system. Unlike wastewater pipes which can be cleaned, water pipes are much more difficult to flush.

You basically need to tackle any mold in your water pipes by pouring a cleaning solution into your main water supply line and then flushing your cold water lines. I would just use vinegar myself but there are some commercial products available. They are all a little too chemical based for my personal comfort.  

How to flush the cold water lines

  1. Turn the cold water faucet for your kitchen sink on all the way and let the water run for one to two minutes to flush cold water through the pipes.
  2. Test the water to be sure it is very cold. This is one way to know the water you are now getting through the faucet has not been sitting in your home’s pipes.
  3. Turn on the other cold water faucets one by one, each for one to two minutes, to flush cold water through the remaining pipes. Make sure to flush the outside spigot, refrigerator (if yours is connected to water), and washing machine.
  4. You can now use your water as you normally would.

Don’t Forget About Your Water Heater!

If you have mold in your water or water pipes then you need to get it out of your water heater. Again, there isn’t some simple and full proof way of doing this. However, there are two options.

The first is to basically drain all the water out of your water heater. You do this by turning on every HOT WATER faucet in your home. Run the water for 15 minutes for a 40-gallon tank or 30 minutes for an 80-gallon tank. Your water heater tank should be completely empty. Allow it to refill. This may or may not solve the problem and is best used for a very minor water mold issue.

For a more serious water mold issue, I would follow the instructions on how to clean your hot water tank with vinegar here.

Speaking Of Wastewater Pipes

It is actually a VERY good idea to clean these once a month. Wastewater lines are VERY likely to develop a mold problem seeing that things like food, hair, soap, scum, and other debris regularly make their way down there.

You need to do this in every sink, shower, and bathtub simultaneously. If it has a drain, do it.

  • Pour ½ cup of properly diluted EC3 Mold Solution OR Citrisafe Remedy down each drain. Allow it to sit for one hour.
  • Boil two cups of water and pour down the drain, then run the hot water from the tap for several minutes.
  • Pour a quarter-cup of baking soda into the drain.
  • Pour one cup of vinegar into the drain and allow it to sit for 30 minutes. This will fizz up which helps to loosen any mold growth inside the pipes.
  • Boil two more cups of water and pour into the drain, then run the hot water for several minutes.
  • Repeat monthly

Important to note! NEVER pour bleach into your plumbing system. It is very abrasive to all pipes.

Can Mold In Water Make You Sick?

Yes it can. Drinking mold or bathing in mold is not doing anyone any favors. Everyone will react differently but there is a 99% change that the mold in your water is causing some sort of health related issue be is mild or more severe.

How Can You Prevent Mold In Your Water?

The number one way to prevent mold in your water is to install a top of the line whole house water purification system that has a demonstrated track record of removing fungal contaminates.

I have tried quite a few systems which failed at this. However, after years of hunting, I finally found a whole house water purifier that will keep unwanted mold spores (along with everything else) out of your water supply. It doesn’t use salt, chlorine, or any other chemical. It truly is the best whole house water purification system on the market. Head over to Pure Effect Advanced Filtration and check out the Ultra Whole House water purifier. Customer service is awesome and will answer all your question. You can then contact your trusted plumber to install this system for you.

If you don’t have the finances or the option to install a whole house water purifier never fear! Pure Effect also offers other various options including drinking water filtration and shower filtration.

The Pure Effect Whole House water purifier

Other ways to prevent mold in your water include:

  • Clean the faucet aerators weekly and replace yearly.
  • Practice good overall mold prevention around the house as well as outdoors. The 27 tips to prevent mold are a great place to start.
  • If you suspect mold in your home, test for it to see exactly what you might be dealing with.

What Is White Water Mold?

White water mold is a mucous-like substance that looks like shredded tissue paper when floating in the water. The color may range from white to shades of pink, violet, yellow or gray tones. It is not the same thing as algae although it is an organic substance.

White water mold forms a heavy, protective coating, providing the organism with an uncommonly high level of protection that is very resilient against both halogen-based (chlorine, bromine) and non-halogen sanitizers and germicides. This means that even if you destroy the white water mold, it can come back rather quickly since it is so resilient.

White water mold can be found on pool ladders, toys, floats, steps, automatic pool cleaner parts, fountains, directional fittings, skimmer baskets, weirs, and garden hoses, etc. Even tiny quantities of it can cause the problem to reoccur. It is usually caused by improper water and pool maintenance, environment and poor circulation. Basically, it is an overgrowth of naturally occurring Biofilms lying on pool surfaces and hiding in spots that are less accessible.

How you remove white water mold depends on your pool or hot tub. Speak with your local pool professional to determine your best course of action.

The best way to avoid white water mold is through good pool maintenance. Don’t slack in this department.

What About Water Bottle Mold?

Water bottle mold is a huge issue. 90% of the time it occurs because of improper water bottle hygiene. AKA – you didn’t thoroughly wash your reusable water bottle at the end of the day. You absolutely have to wash every square inch of it, especially if it has a flip top to drink from. (The other 10% of the time it is because you have mold in your water supply).

Biofilms and other materials from our mouths cling to our reusable water bottle like a dung beetle clings to, well dung. You have a nice wet, dark environment with food for mold to flourish in.

Jason Tetro, microbiologist and author of The Germ Files shares some great information about water bottle mold.

It takes a few days, most likely—unless it’s sugar water, at which point it’ll grow within 48 hours. Usually it’s over the course of five days, which is usually how often people wash their water bottles. At that point there’s as very good likelihood you’ll have some kind of growth.  One method of growth is on surfaces. The inner surface of a water bottle can essentially harbor biofilms, and these will allow numerous different species—including bacteria and fungi—to grow, and they’ll be able to stick there because biofilms are very sticky. So even rinsing and shaking your water bottle may not be enough.”

Then Tetro mentions “floaties,” a term he coined for the mold that floats on the top of the water’s surface.

These are the bacteria and fungi in the water itself. This is more rare, because you need to have a high level of food in there.”

Tetro also shares the best way to prevent mold growth in your water bottle.

You’re going to have to clean it manually. Use a brush, some soap, and hot water. If water is over about 160 degrees Fahrenheit, the bacteria and fungi won’t grow—they die. So the best thing for you to do is boil water and put it directly into your water bottle and fill it straight up to the top. Add a little vinegar if you want because as an acid it helps to break up some of the stuff. Then let it sit for about three minutes. That’ll pretty much kill everything. And if you’ve gotten rid of the biofilms with a brush and on the lip with a towel, you’re pretty much going to have a clean water bottle.”

If you have a bottle with a very small mouth opening, he advises to use your fingers to get underneath the lip.

How To Test For Mold In Water

There are a few options when it comes to how to test for mold in water. Testing for mold in water is actually pretty easy. If you have children, you can turn this into a science experience. Let’s look at the first method.

How To Test For Mold In Water With Petri Dishes

  1. Purchase these petri dish style plates. Do not substitute with another type of test plate.
  2. Open the test plate.
  3. Use a clean eye dropper or pipette like this to transfer about 10 drops of water (taken directly from a running stream of water from your faucet) onto the surface.
  4. Replace the lid, tape it shut and wrap it in foil.
  5. Place the test plate in a location that stays room temperature. Do not move the sample for 5 days.
  6. After 5 days gently lift the foil and check the plate for growth. If there is none leave it an additional 2 days for a total of 7 days.
  7. If after 7 days there is no growth then there is no mold in your water. If there is growth, repeat the test with a new test plate to either confirm the original results or rebuke them.

There are some HUGE limitations to this water mold testing method. First, cross contamination is a big risk. Second, you might get mold growth but you won’t know what types of mold are in your water. This could make a difference in how you go about dealing with the situation. Third, there are a lot of false positives. It is a great way to rule water mold IN but not the ideal way to rule water mold OUT.

My Preferred Way To Test For Mold In Water

If it were me, I would use the Tap Score Mold and Fungus Water Test.

It is very affordable and very accurate. Tap Score’s Total Mold Test will analyze your water quality for mold and fungal contamination. This popular water quality mold test includes species like black mold, (Asp. spp.) and other Aspergillus formations with full speciation of the Penicillium & Cladosporium genus. Results will be reported as a quantitative fungal analysis, measuring your detected species in units of colony forming units per mL (CFU / mL).

Tap Score also has all kinds of other great water tests. You can test for Glyphosate, Radon, Plastics and Microplastics, and so much more! You can even test your favorite bottled water! Check out all their tests here.

Glass bottle with water droplettes falling into them. Looking at mold in your drinking water.

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23 Comments

  1. I need help ASAP. I ha e 2 daughters and can’t seem to get to the bottom of the problem.
    I can send all reports to you and although it has remediated, I still feel like I have it and surface mold is showing up everywhere.
    My father in law owns the home. He won’t entertain any more testing and I’m about to go crazy. My husband thinks I’m paranoid but there are clear signs it’s still here. Can you please direct me to someone who can help? I swear, I take a loan to fly you out here!! I’m desperate and hopeless.

    1. Hi Brandy! I am sending you an email. Let me know if you don’t get it please.

  2. Jerome Dsouza says:

    Very well written. Very informative and helpful.

  3. Rebecca Gardner says:

    It was interesting when you explained that mold will only grow in water if it’s at rest. My husband and I want to hire a cleaning service to save us time and effort when we move to our new home with a large backyard pool next month. Asking about how mold growth is prevented should help us choose a knowledgeable pool service, so thanks for teaching me how to evaluate their answers!

  4. I have mold in all my water lines due to an old filtration system that was attached to the main line coming in to the house. It developed mold and transferred, so we seem to have it coming in everywhere. I have read of shock chlorination treatment. Short of replacing all my lines and my water heater, what can I do?

    1. Hi Dawn! What a mess. I am sorry you are having to deal with this. Did you read the option of the article where I discuss how to clean your water heater? Definitely do that! In your case I think you are going to need to do a shock chlorination treatment and then follow my instructions in the article on how to flush your cold water lines. I would absolutely test your water after doing all this!

      1. I am trying to read the article on how to test for mold in your water, but I can’t get the article to pull up. Please help. Thank you!

        1. Oh my gosh! Thank you for telling me! I have no idea what happened but I restored the article.

      2. Hi, Jennifer. Thank you for replying. I read the water heater article and the instructions for flushing water lines, but I don’t understand how/where to access the cold water line to flush it. I am on municipal water. How would I force/flush my lines??

  5. Esther Jo says:

    There are a couple of faucets in the house-one in the basement that we rarely we turn on. If we don’t use that faucet, will that pipe harbor mold because water is just sitting there? If that pipe harbors mold, then can that pipe affect all the water going through other pipes into the house? Would to email you other concerns.

    1. Hi Esther! A pipe won’t grow mold simply from not being used. However, if moisture is constantly inside that pipe because it didn’t drain out, then yes, it can grow mold if spores are present. As for pipes with mold impacting your entire plumbing system… it all depends on how your pipes connect. If water has to travel through the impacted pipe to reach other area of your home, then yes, it will effect all the pipes.

  6. We have city water and live in the suburbs of a large city. Our home is 20 years old.
    I have always tasted the bleach/chlorine of our city water but last fall, I started tasting mold in the no-filter ice maker cubes. I turned it off and started using a manual fill tray. In doing so, I switched to my RO water and it all tastes fine. But recently, my daughter used the tap water to fill it and yuck!! Mold taste again.
    My water heater is original to the house. I smell it now in the hot shower too. But it definitely comes out of the cold tasting like mold. Where should I start looking for the source of the problem? We have three bathrooms and kitchen but 6 people so none of our faucets ever sit idle long. I don’t want to just slap a carbon filter on it for taste and still have the problem.

    1. Do you know what your main water line is made out of? Copper, pex, etc…?

  7. I had our home tested for mold and 2.4 million mold spores were found with 8 different molds all producing mycotoxins and one was actively reproducing. My eldest daughter as well as my 2 other children were heavily exposed, but my eldest daughter has been diagnosed with autism since she was 4 and is 15 now and after this exposure has developed seizures that only started since I uncovered the mold August 2021. My first born and only son shows signs of Alzheimer’s and he is only 18. I cant get any help from anywhere, I couldn’t afford the testing and we were homeless from August until November and now we are in another home full of mold. The ambulance has been to get my daughter almost a dozen times since we moved in. I just need help getting my kids tested and treated as well as in a mold free environment. If you have any suggestion please let me know!

    1. Holy wow! That is an absolutely insane amount of spores. My word! You absolutely need to work with the right practitioner on this. I highly recommend Elizabeth. She is hands down amazing and does offer complimentary consultation to see if she is a good fit for you and your family. I have worked remotely with her for years. http://wellnessimages.com/functional-health-consultation/ She is conservative in her approach and won’t break the bank. 😉

  8. Hi Jennifer. I’m hoping you’ll see this (and respond). First, thanks for all of the helpful tips. In this article you you say to pour a cleaning solution – I plan on using white vinegar – into the main water supply and then describe how to flush out the system. 2 questions:
    1) How do you add the cleaning solution into the main water supply? My mold source is the water softener salt tank. I will be replacing the tank and will then need to purge the water supply and will also remove and purify the shower head and faucet screens with white vinegar. Basically, the water line goes from my well to the pressure tank and then heads to the water treatment/filtration and then to the rest of the home – I’m not sure how to pour vinegar into the main line. Currently I have bypassed the treatment/filtration system because of the mold in the water softener tank.
    2) How much cleaning solution? Are we talking one teaspoon of vinegar? 10 gallons? A pneumatic trailer of vinegar carried in by an 18 wheeler? I hope you’re smiling at the exaggerated examples! I just want to do this once and do it right – hence the questions. Thanks in advance for any insight you can give me.

    1. HAHAHAHAHA! Yes let’s go with the pneumatic trailer option. 😉 Can you email photos of your setup please? jennifer @ moldhelpforyou.com Also please tell me how many square feet your home is and I can roughly guess what your needs are for vinegar. Thank you!

  9. Hi Jennifer – found your website & info informative, thank you! Hoping also for your opinion.

    I have spurts of black water that comes out bathtub faucet at any given time, no pattern i can identify, happening start/stop cycle over last several yrs. Sometimes a substantial amount, other times no spurts but you see black floating little specks in bath tub water. Dont see from other bathroom or house faucets, unless we’re unable to detect it. spurting doesn’t seem to happen out of shower head but again, little specks may not be detected.

    Had plumber here 1x a few years back, hot water heater was flushed. Seemed to stop for awhile but now back again. Water heater 8 yrs old, installed in 2014.

    Does this sound like a water heater problem or possibly mold in pipes or faucet(s)?

    1. Hi Liz! What kind of pipe do you have coming into the water heater? This is likely either an issue with that specific pipe or the water heater itself. In theory your water heater is still “young” but honestly, I am seeing water heaters start to fail sooner and sooner these days. Usually the black specs indicate corrosion from a pipe that feeds the water supply. Do specks ever come out with cold water or just hot?

  10. Jane Nuttall says:

    Hi Jennifer,
    I am hoping you can help me with a stick issue (moldy). I lived in moldy trailers for 30 years. Had chronic health conditions including chronic severe insomnia, nausea, migraines, vertigo and the list goes on. Then 2 1\2 years ago, the mold got so bad the floor tore open in my bathroom. After that, I got deathly ill, almost died and had to move and leave everything behind. I had no insurance, so the financial loss was great. I have been trying to recover from all that, and I moved into a newly constructed studio apartment. Then, about 3 months ago, I started noticing a moldy smell in my shower. I could not see the mold, but I could always smell it, and I couldn’t figure out where it was coming from. Then one day while I was in the shower, I noticed that the water itself stunk. I had also been noticing brown water coming out when I turned the water on. I realized that I had forgot to change my shower filter for a year, and so figured that was the culprit. During this time, I was getting sicker by the day. After changing the filter, the problem did not go away. I finally got someone to cut into the bathroom wall and check the pipe between the shower and the tub faucet. It was full of black mold. I had the pipe replaced, but I’m still worried. What if it spread farther down into the pipes? I have been so deathly sick, I don’t want to take more chances, but I am a widow with little to my name. I have tried to bring it up to the house owner, but they couldn’t smell the mold when I could.
    Since the pipe was removed, and the filter removed again, I can’t smell anything in the shower now, but I want to make sure. I have looked at your website, and I saw the testing that can be done, but again, I cannot afford it
    The pipe that was replaced was plastic, and I had it replaced with copper because I read that mold does not grow as easily on metal, but what else to do?
    I read about testing water on your website, but I cannot afford anything expensive. I am going to have to have my entire house deep cleaned. but I am too ill to do it. Do I need to worry about mold growing in the pipes farther down that are full of water? What to do?
    Thank you

    1. Hi Jane,

      I am so sorry you are dealing with this. If there is an issue inside the main water line it doesn’t sound like the homeowner would replace it. Testing the water is really the only way to know what is going on inside the pipes. I would suggest calling the water testing company and explaining your situation and seeing if they can offer you a discount.

  11. I have mold in my water supply pipe lines to my condo due to an unground tree stump in front of my condo that sits above the municipal water pipe lines that run into my condo building. The pipes go into my condo townhouse first, then branch off to the 3 condos next to mine. The mold levels are highest in my condo. The tree that had been there was neglected and developed a fungus problem. The condo board and property manager had it cut down but didn’t and wouldn’t grind down the tree stump. I discovered we had mold in our water lines after a main line shut-off valve got a pin hole leak and mold grew out and all around the valves.

    Via research I learned that unground tree stumps are a main way that mold gets into water supply pipes. The stump being cut attracts mold and bacteria. The tree roots keep growing, find a crack in the water pipe and grow into it, thus providing a continual supply of mold / fungus and bacteria into the water pipe line. The water doesn’t need to sit stagnant for long – provided it has the tree roots in the pipe to provide the ongoing source of mold spores and bacteria.

    This situation needs to be addressed and discussed more, as it’s rare to find anyone that knows about this. Mold inspectors – plumbers – home inspectors – heck even our municipal water department doesn’t know much about this. My neighbor and I now know why our water has smelled and tasted funky. Despite repeatedly sanitizing my washing machine and dryer the moldy “funk” smell wouldn’t go away. No wonder I’ve been so sick! I was brushing my teeth with moldy water. Showering in it. Cooking with it and drinking it. We have a mold problem in our building, too, due to water intrusion, lack of attic ventilation AND mold in the water. And we have a condo board and property manager who refuse to address it.

    Thank you for your website and information. Thankfully the tide is turning on awareness of mold – mold illness – etc. There are too many mold “inspectors” who don’t really know what they are doing, from my personal experience. There needs to be a national licensing standard IMO and more women working in this field!!

    1. Hi Rita! Thank you for taking the time to leave such a thoughtful comment and to share your experience. I agree that there is a lot of variation in terms of the caliber of mold inspectors out there. While I believe personal experience with a major mold situation is invaluable in the profession, there are ways around that with the proper training and coursework. So many of the “best practices” are antiquated. I also strongly believe that every building is different and you really have to take the time to understand the building. I am always looking at what will work best for a situation versus what the standard practice is. I want to find answers for my clients at the best price point possible and in the least amount of time whenever possible. Taking the time to listen to their history is always important. Most mold inspectors can care less about your story. I care about my clients and I want them to have a safe living space that they are confident about! It is why I choose to get into this field. Plus honestly mold is just fascinating. We are still learning so much about it!