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Thread: Black Spots in Bathtub.

  1. #31

    Default Black Spots in Bathtub

    Please allow this newby a contribution to the mystery spots thread. My tub is also a sufferer of the dreaded black spot disease. When I found this forum and realized the extent of the problem, I set out to find the best method of getting rid of these spots (Always have loved a challenge).

    I have no solution to the origin of the spots, however, I have discovered an easy method for getting rid of them, once they occur. Get yourself a Mr. Clean Magic Eraser! Get the kind with the blue scrubber side and the Febreeze air freshener. This product took care of the spots easily. No additional cleaners needed. Find them in the laundry/cleaning aisle at the grocery store. You'll love these little sponges so much you won't be able to stop at the bathroom.
    Happy erasing!

  2. #32
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    I have seen this exact problem , related to deterioration of the inner lining of a black nylon braided supply line.

    Try this. Do not run any hot water for several hours. Then put a bucket in the tub and run hot full blast. See if you get any blackish stuff in the water.

  3. #33
    Master Plumber Redwood's Avatar
    Join Date
    Dec 2007


    I have also seen this problem cured by HJ's suggestion of replacing the magnesium anode rod with an alumininum one...

  4. #34

    Question I have the black stuff too, but...

    Our tub has had this problem for over a year now. It only comes out of the hot water tap and once out of the shower head. The only thing different is that we don't have a regular water heater, we have a tankless heater, or an "on-demand" system. I don't know if that makes a difference in what is possibly causing the problem.

    Also, and I don't know if this is related but our hot water tap for that tub has always had poor water pressure. The cold is fine and all of the other faucets and the other shower has great pressure but the tub has slow pressure only on the hot water.


  5. #35

    Default Black Spots in Bathtub - Possible solutions

    Same problem here. I have a 2 year old home with a water softener and hot water heater expansion tank. I would like to know if everyone involved have either of these additional items.

    I contacted my builder's plumbing company and they told me that the black particles are dead bacteria in the hot water heater. The cause is due to the hot water heater being set to high (would like to know for those affected if their setting is above the med temp (B) or not. Solution was to drain/flush the tank for 10 mins and set the temp gauge between (A) and (B). (I did but still see particles sometime - not sure if I flushed the tank well enough).

    My gut is telling me that it has to something to do with the expansion tank. For awhile, my water softener was set at a higher than normal setting and I believe that this may have damaged the expansion tank. I will do the tap test (as someone suggested) this evening and see if it sounds like the tank is full of water (if so, the tank is bad) and I will replace.

    Lastly, the best solution to remove the black marks from you tubs is from the automotive section at your Wal-Mart or car parts store. Look for Bug and Tar removal/cleaner. It comes in aerosol and spray. It really cleans up the mess and doesn't appear to harm the fiberglass finish.

    I hope this help and if anyone resolves the problem, pls let us all know.


  6. #36

    Default Plumber says black spots are broken up washer

    he asked me to run the water from the tap for 10 minutes and see. it workd so far only 1 black spot instead of hundreds. i dont want to have to do this every time, however. the faucet is a big one and runs a lot of water. and this seems to happen if you dont use the tub for about 2 weeks. i travel, so when i am out of town it doesnt get used.

  7. #37
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    Quote Originally Posted by ladysawfan View Post
    and this seems to happen if you dont use the tub for about 2 weeks. .

    Seems to be much agreement that it is rubber deterioration. Classic symptom is that if the faucet is used freqently, the disintegration is gradual and not noticed, but when undisturbed for hours or days, then the tap turned on...a great deal of the material breaks loose.

    The places you would find a rubber lined hose are the water heater flex connector, and if this is a roman tub...there might be such a hose under. Have you checked either of these?

    Certainly a rubber washer like in a tub valve could also be the problem. Is it a single handle tub/shower valve? Likely not rubber. But if it is a 2 or 3 handle, take out the hot stem and inspect for a rubber washer.

  8. #38

    Default Black Specks that wil not go away

    I too have same problem and just ran across this site....I've read all the posts, and still appears that there is not a permanent solution. These little black dots/specks are extremely hard to remove from fiberglass tub & surround. I've used bleach (although hesitant too since have septic system) and other cleaning supplies but still will not remove unless I actually use my fingernail and "pick" / scrub them off.

    These only appear in the bath in the basement. The house is 10 years old and the water heater is only a few years old now. No rubber gaskets anywhere in plumbing that I know of (except for O-ring to seal water filter and that is brand new).

    I certainly think that it is a micro-organism of some sort as others have suggested, but am stymied as to why no cleaning solution, esp. bleach does not even "touch" these things.

    Many of these are on the shelf of the surround where what does not hit so do not think it is coming from water heater or the water itself. Also, the hot water, as well as cold, appears crystal clear in a glass.

    This almost looks like black over-spray from an aerosol paint can, if that helps.

    Thank you for all your help.

  9. #39

    Default Same "greasy" black spots -Gone (maybe for good??)

    After reading these posts & talking to AO Smith water heater support the only
    source of rubber in my copper H20 supply is the plex connectors. AO Smith said the Anode usually causes "smelly" water.

    I replaced the plex connectors with flex copper connectors and no more specks in the hot water to the washer or the bathtub. I will give this at least several weeks before declaring a solution but all is ok after getting rid of the plex which was in sorry shape on the interior.

    The specks,flecks I had were black floating which would smear on the porcelain
    very difficult to cleanup. So far several hot water tests in the bathtub & washer
    with not repeat of the problem.

  10. #40
    DIY Member foxhome01's Avatar
    Join Date
    Aug 2008
    North Carolina


    This has been and on and off issue for us. We first noticed these smear-like specks about a year ago. Replaced expansion tank and anode rod. Came back a few months later and brought along larger specks but these larger one's didn't smear.

    We wound up replacing the PRV on the main line thinking it was the rubber from there (but honestly, it didn't even look that bad) and while we don't have the large specks any longer we still see the smear-like specks in the bath tub and dishwasher.

    I think I will say that it's no where near what it used to be...but it's not resolved. We are starting to see the black specks also on hand rags that we would use in the shower and the tub (it's not mold, which I thought could have been the case...too many rags it's happening too) ODD...very ODD. Especially since we can't really see them until afterwards. We can't see it when we run the tub/shower. It sort of just shows up and is there ready to be smeared.

    I had lowered the water heater some since it's summer time and within a week of doing that we saw an increase in the smear-like specks. Increased the heat and there's a decrease but still exists.

    I'm not sure there's been any resolution for some folks dealing with this.

    As for cleaning the buggers, the only thing I found that works is soft scrub but I have to scrub real hard to get it removed.

  11. #41
    DIY Junior Member
    Join Date
    Sep 2009
    Berkeley, Ca.

    Default What are Plex Connectors?

    My question is in response to the post by "pd". What is a Plex Connector? I've done some searching on google and not coming up with anything. Are you referring to the flexible water supply hose?

    By the way, I am so surprised to hear so many people with new houses complaining of this problem. I have an old Craftsman, 1914, and have been thinking that it is the old pipes. But, over the past five years a number of remodeling projects have happened, except there hasn't been any new plumbing installed, just new fixtures with a little bit of copper piping attached to the old galvanized pipes.

  12. #42
    DIY Junior Member Mouse100's Avatar
    Join Date
    Apr 2010
    Blog Entries


    Quote Originally Posted by BMWGreenRT View Post
    Some background info first.
    I am in a brand new home, my water heater is a Bradford White 50 gallon.
    It has a powervent installed. The 2" into 3" PVC vent pipe goes up about 2 feet and then horizontally for about 15 feet where it vents out of the basement wall.
    I have a 72" by 48" fiberglass tub in white.

    I have the unit set above the normal heat to a hotter setting, but not the highest available.

    We are on City water not a well.

    I have noticed little black specks on the bathtub recently. There is no shower in the tub. They were not there for the first three months of use. When rubbed they spread like ladies mascara would spread. It takes some rubbing and cleaning to get rid of them.
    I thought at first maybe it was some kind of mold, but since it was only inside the tub, I decided to clean it with a 50/50 bleach water mix.
    I let the tub sit for 3 days and nothing else appeared.
    But once I filled the tub again with hot water, the little specks appeared again.
    They are not in the sinks or toilets.
    The toilets "do" show a very light pink colored ring at water level if not flushed for a couple of days, which cleans off very easily.

    Does anyone have any idea what this is called, what causes this and how I can get rid of it.
    All help would be appreciated.
    If you need more info please ley me know.

    I have the same problem... only the water from the hot water side comes out with a black tint to it... leaves a black greasy residue all in the tub... it's hard to clean because it smears like eye makeup... We changed out our hot water heater at a cost of $ 300. and it didn't work... then nt husband put a new anti rod or whatever that thingy is called on the new hot water heater.. I couldn't take a bath if I wanted to... water is filled with black greasy stuff... does not happen in shower... I wish someone new how to fix this problem! Also we have city water not a well. I don't understand why it does not happen in the cold water doesn't it all run through the same pipes? Very disgusted with this problem!
    Becky from Texas

  13. #43
    Master Plumber Redwood's Avatar
    Join Date
    Dec 2007


    Nope, HJ and Plumguy pretty much nailed the possible causes.
    It's either magnesium sulfide from your water reacting with the anode in which case an aluminum anode is the fix.

    Or there is deteriorating rubber somewhere. Chloramines used in water disinfection attack rubber causing it to breakdown. It may be from inside a flexible supply for a water heater, an expansion tank, or even valve parts...

  14. #44


    During our research of this problem, we came accross this report out of Florida: http://www.psc.state.fl.us/utilities...inalreport.pdf

    The report lead us to believe black water from copper pipe corrosion and the resulting residue or sediment from this corrosion, combined with the the use of water softeners had contributed to black spots on our clients bathtub and shower floors. Our client disconnected the water softener and flushed the copper pipes resulting in a fix. This may not solve everyones problem.
    Last edited by ksrountree; 08-30-2010 at 06:44 PM. Reason: misspelling

  15. #45
    plumbing contractor worsnup's Avatar
    Join Date
    Jun 2010
    phoenix az


    you have plastic or pex water system, its algae and its common in plastic systems in phoenix

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