View Full Version : Black deposits in low flow toilets

12-13-2004, 01:30 PM
This question was asked in July 2001 by another woman but got no responses. Now, I am having the identical problem. She wrote, "Has anyone else experienced a problem with nasty black deposits at the waterline in the bowl of a low flow toilet? Ever since my apartment bldg replaced our old toilets with the low flows, I've had these black deposits appearing almost daily. I thought they were mildew stains, but mildew removers like X-14 have no effect. They come off easily with scrubbing, but I've found no way to keep them from coming back. What causes them? What can I do to prevent them? " In my case, I recently purchased a new house and all three toilets develop these nasty black streaks. They wash off easily but are really disgusting. Is it the pipes, or is it the toilets?

12-13-2004, 02:25 PM
This is just a guess...do you use one of those cleaner tablets or other dispenser devices that sits in the tank? the black could be rubber deposits that are being eaten up by the excess chlorine from those devices.

12-13-2004, 03:00 PM
I have never used a product that sits inside the tank. All I use is a pine-scented cleaner and brush. It is a mystery. The streaks that form in the tank come from the small holes underneath the rim. Sometimes the black substance forms a ring at the water line first, then it forms lines down from the holes to the water line. Other times, the streaks will "grow" from under the rim and ultimately reach the water in the bowl. Once the bowl is cleaned it takes approximately 2-3 days for it to start all over again. I have never, ever seen anything like this. I am beginning to regret purchasing this new house with low flow toilets.

12-13-2004, 03:19 PM
Is the surface (i.e. the path between the rim holes and the waterline) etched or rough there maybe from mineral deposits? If so it could be allowing small amounts of moisture to stay on there (instead of running down into the water). This would be especially pronounced if you flush that toilet infrequently.

I had a similar issue previously, however it was a type of mildew/mold and seemed to crop up a certain times of the year (not sure if because of the water or the environmental conditions). In my case, it seemed to accumlate where someone had apparently scratched the bowl serface with a rough brush.

I ended up replacing the toilet and problem was solved.

Here is one thing to try to verify it isn't mold/mildew, go ahead and use a "blue" cleaner/dispenser. I'd bet if it is mold, normal flushing will probably eliminate or at least retard.

12-14-2004, 12:38 PM
I am willing to try almost any suggestion. The house is only four months old. All of the toilets are new. This problem has been occuring since the day I moved in.

12-14-2004, 04:05 PM
I don't think that you can attribute the stains to the toilets, or everyone would see the same thing. My guess is there is something in your water. If you take a glass and fill it with cold water from the tap then let is sit for several days - leave it for up to a week or so. See if you get similar things.

Maybe someone else will have an idea. Did you say that others in your neighborhood have similar problems? Maybe you should take it up with the city or town water people .

12-15-2004, 06:11 AM
I have asked three other neighbors and none seem to have this problem (or they won't admit it.) In the last two days I have had a plumber, then his supervisor, come to the house to investigate. Neither one has seen anything like this before. The supervisor said to try a bleach-type tablet in the tank. His reasoning was that low flow toilets do not eliminate all of the water in the tank with each flush - and that might be promoting a mold/mildew buildup. The second plumber checked the inside of all three toilet tanks and he also went into the attic to see if the water heater had any type of residue in the pan. (To be honest I'm not sure really why he went into the attic or what he looked at...) Everything looked clean. I have decided that low flow toilets are not all that great and I would prefer to have traditional toilets in my home.

12-15-2004, 07:46 AM
None of the toilets exchange all of the water with each flush. They do flush all of the water out of the bowl, but there is always a little left in the tank (some more than others).

Gary Slusser
12-15-2004, 08:20 AM
Bonnie, it's a water or air quality thing and has nothing to do with the toilet type unless there is 'rubber' deteriorating in the tank; again due to water quality. How will you feel after replacing these toilets and still having the problem? Are you on well or city water? City water with chlormines in it is very hard on 'rubber' gaskets and seals. It causes black smears that are hard to get off, so I suspect you have some type of air borne something.

Quality Water Associates

12-19-2004, 06:49 PM
And, like them or not, low flow toilet are now "traditional." Unless you get illegal imports from Canada that still flush with 3.5 gallons, in the U.S. we're stuck with 1.6 gallons (and some newer ones even less).

12-20-2004, 07:40 AM
I relate these complaints to rubber dissolving somewhere in the system. While you maybe only notice the black marks in the toilet bowls they may also be occuring at other fixtures but because the water does not sit, it is not noticable. I would take Jim's suggestion to let a glass sit.
I would not think the residue is due to the toilets. More likely it is related to the toilet supply tubes if it is not occurring at other fixtures.

12-22-2004, 12:53 PM
I will try jadnashua's suggestion and let water sit in a clean cup for a week to see what happens. I will post the results of my "experiment" next week.

12-22-2004, 02:16 PM
Someone else suggested it, but you may have missed it - many people use the flexible hoses to connect their toilets to the shutoff valves. Some of these are better than others. Some places also sell some that are not rated and certified - thus, the quality of them and their components may be suspect. They're only a couple of bucks - you migh want to consider replacing it since the interior of the hose may be the source of the black marks.

Also, take the top off of the tank, and lift up the flapper valve. See if you have black crud on it. If you do, replace the flapper valve. This rubber may look okay, but be deteriorating. I've seen some that just felt slimy, not from contaminants, but just from decomposing in the water. Rub your fingers over both the top and bottom of the flapper valve. And last, the rubber bushings that go around the bolts thathold the tank to the bowl could be in the same state - i.e., soft and slimey. They may need to be replaced.

01-05-2005, 12:31 PM
The customer service department for the house builder has arranged for someone to come to my house tomorrow to test the water in the water heater. I have not spoken to this person directly, but I was told by customer serivce that perhaps there is bacteria in one or both of my water heaters causing gunk to come out the toilets!?! If that is true, then my drinking water must have gunk also! Can water heaters that are only a few months old become contaminated like that? If so, what are the options to correct the situation?

01-05-2005, 12:52 PM
Water from the heater does not go to your toilets. There is either a major miscommunication or you're talking to the 3 stooges. I cannot believe the service department of your builder includes a licensed plumber.

01-05-2005, 01:11 PM
I notice black crud at the water line in two toilets that I see often.

One is the American Standard Glenwall (http://www.terrylove.com/forums/showthread.php?t=25073) and the other is the American Standard Champion.
Other toilets in the same households but of different brands do not have the black crud.

Dale's Plumbing Service,
01-05-2005, 02:55 PM
well after reading all these threads I would say that it is the supply tube that supplys the water to the tank. I have that problem in my shop on city water. I used a bif braided water supply tube. It also may be coming from one of the componets in the tank. I suggest useing copper chrome supply tubes.
:) :)

01-05-2005, 06:37 PM
If someone else told you this already, I missed it. Do NOT (ever) use those clorox cake type tablets in your toilet tank (a plumbing supervisor advised this?) Virtually all toilets come with labels telling you not to use these, the blue liquid stuff or really anything else that goes in the tank.
What brand is this toilet?
The Pipewench

06-17-2008, 05:26 PM
I have lived in this house for 14 years and never had any problem with my old toilets until I recently replaced all 3 toilets; 2 with toto low flush and 1 with Kohler low flush. Now have these nasty black mildew-like spots that show up every couple of days in all 3 toilet bowls right at the water line. You're right, it's disgusting. Was recently diagnosed with diabetes, and was thinking that maybe the sugar in my urine was causing it...until I read Bonnie's posting. Also my Doctor says he's never heard of that. I scrub my toilets with scouring powder AND with a pumice stick to remove hard water deposits at the water line, so there's nothing that would cause anything to "stick" at the water line. Does anyone know what causes this? Grateful for any advice. Thanks, Nancy

06-17-2008, 05:44 PM
I"m not a fan of pumice or powders.
They will scrape up the bowl, and give more traction for stuff to hang on.
I like to use the liquid cleaners that some some sterilizing power. Lysol and Clorox are two I've used.

06-18-2008, 06:03 AM
There are some aftermarket systems that fit in line with the refill tube and run bleach, cleaner, or enzymes down the overflow. Fluidmaster and Kaboom are two brands. I Emailed Toto about these. The representative who answered said that Toto doesn't officially recommend anything at all in the tank, but since these products don't contact the sensitive tank parts with chemicals, he would try them in his own toilet. Might be worth a try.

06-18-2008, 05:59 PM
I thought I would post some gross out pictures on this subject. This is a Toto Carlyle toilet and it does grow grey spots that will eventually turn black if left go long enough. The first three pictures are what has grown three days after washing down the bowl with a high pressure spray.




06-18-2008, 06:00 PM
The next two pictures are ten minutes after applying bleach.



The last picture is after flushing the bleach once.


I did not brush this at all. I have found that even when doing a thorough job of cleaning with brushing and a ten minute bleach treatment the spots will return in about three to five days. Is it something in the water or something that I have previously eaten? I don't know. I figure it is just a reminder to clean the silly toilet at least once a week.

This will easily brush out and leave the porcelain shining.

06-18-2008, 06:47 PM
Likely in the water. Is this municipal supply, or from a well?

06-18-2008, 08:20 PM
It's municipal water. Don't misunderstand me, I'm not complaining. I just wanted to post this as an accompaniment to the other posts describing "spots growing in toilets".

06-19-2008, 07:00 AM
I have two properties, a condo on a regional water system that serves most of the county and a seasonal cabin with gravity fed water from a brook.

One might think the brook water would stain, but have a look at the pictures. At the cabin I can get away from having to scrub the toilet bowls often as compared to the condo.

If the toilets sit unflushed for a week or so at the condo, a deposit begins to form from the water. In the case of my stained toilet, it sat for a couple of weeks.

Since I have been staying overnight at the condo on "work nights" to save gas and money, the staining is not as bad. I keep a bottle of bleach in both bathrooms at home and give the bowls a treatment which eliminates the stains.

I do not use bleach at the cabin because I don't want it in the septic tank. But there is no need for it or acid based cleaners because the water doesn't appear to have anything in it that would deposit.

The photos of my Antique China are from 2005. The 1936 Standard in the condo has been replaced in March of this year with a Cadet 3 (to reduce water bill). The 1952 Gerber is stored away in the Hutch and a 1952 Eljer siphon jet is in its place for its rotation on the Hot Seat. The 1957 Eljer in the shed facilities is currently in use. The antiques reign at the cabin and are rotated almost annually for my enjoyment and for my guests to appreciate (and they do)!



06-19-2008, 07:41 AM
I get similar things in mine if they aren't flushed frequently...it's totally a water supply thing, and has nothing to do with the individual toilet. I will say that on the Totos I have with SanaGloss, it just swishes off with an occasssional brush where I had to scrub a lot on the old, builder supplied toilets. In addition to that, I get iron reducing bacterial deposits (orange ring). Bleach helps tame that for 2-3 weeks.

09-26-2008, 05:47 PM
I've recently moved into a two-year-old house. I have a situation in which I have two toilets in opposite sides of the house. One is fine, the other develops black streaks that won't come off with bleach, Comet, Soft Scrub, Magic Eraser or CLR. Why one and not the other?:confused:

11-16-2008, 08:51 PM
I have two Toto toilets. One gets the black deposits, one does not, so I think the problem comes from the toilet, not the water system. The one with the problem also is having a problem running after it is flushed. It has had more use than the other toilet, so I think something needs to be replaced, which hopefully will stop the running and the problem with the deposits. Both problems started around the same time.

01-08-2010, 03:44 AM
my partner has diabetes and works away, we only get black deposits when he is home. This occurs with alot of people with diabetes. I thought it was worth mentioning.

05-20-2011, 07:57 PM
I too have a new home with the low flow toilets. I have had these DISGUSTING water lines ever since I moved in. In 23 years at the old house with the old toilets, I NEVER had this problem. Any suggestions on how to fix this problem?

05-20-2011, 10:32 PM
my partner has diabetes and works away, we only get black deposits when he is home. This occurs with alot of people with diabetes. I thought it was worth mentioning.

That's interesting. One of the home with black mold, there is someone with diabetes. The other home doesn't as far as I know. Though the last time I checked there, the mold line was gone.
I don't have it where I live, so it is kind of odd when you see it. Two of mine are the 1.28 gallon flush.

Jimmys here
06-17-2011, 01:43 PM
As for mold rings in the bowl, they can either be iron or other mineral deposits from the water supply, or mold growing in the spouts where the water enters the top of the bowl. I greatly reduced the black mold problem by using a steam cleaner and applying steam to the water spouts at the top rim of the bowl. I suspect one could use a spray of acidic solution like white vinegar or diluted muratic (swimming pool) acid but since I had a steam carpet cleaner that application really worked well. The mold will eventually come back but it is a very light case indicating a bowl cleaning is due. As an interim step a few drops of clorox into just the bowl will stop the growth of rings but be careful not to use too much if you have a septic system, chlorox can damage the septic system.

As for the black mold line at the water surface inside the tank, I did two things. After turning off the water, flush the toilet, use a small paint brush with chlorox to kill the mold. Then I wanted to seal the porous tank so I dried it with a fan for a few hours then painted the inside of the tank a few inches above and below the normal water line with a two coat epoxy paint. This paint should at least remove deep seated mold by filling the porous ceramic surface. Next I plan to occasionally empty the tank and steam clean the surface at the water line.

It seems the mold must be a product of limited air flow in the rooms and spores in the environment combined with the tank temperatures. If my attempts to reduce mold don't take care of the problem there are more solutions available but they get into more expense.

As others have said don't use any strong chemicals inside the tank. They usually make the flapper brittle and unable to seal, allowing leaks. Also chemicals will rust out the bolts holding the tank to the commode. I speak from personal experience...

11-26-2011, 03:29 AM
my partner has diabetes and works away, we only get black deposits when he is home. This occurs with alot of people with diabetes. I thought it was worth mentioning.

I have diabetes, other in my family don't. I use one toilet consistently, others use the other toilet. We have black deposits ONLY in MY toilet. Both toilets are identical, use the same water supply, were installed at the same time, and are cleaned with the same frequency using the same methods.

11-26-2011, 05:27 AM
I have diabetes ( type 2), but well controlled. I don't have any issues. I try to stay abreast of diabetes issues, and this is a new one on me....why would anything in your system cause a ring? Could it be the meds? It would be worthwhile checking forums at the American Diabetes Association ( diabetes.org) or Taking Care of Your Diabetes ( tcoyd.org)