brown stains on bottom (pebble tec)

Stains on the pool surfaces, pool equipment
or on the swimmers, or off-color swimming pool
water. Discolored but clear pool water.

Brown stains on bottom (pebble tec)

Postby Guest » Wed 27 May, 2009 10:05

Swimming Pool Pro, Chlorine is added through skimmer(3'Tabs) Total chlorine and Free is 5.0,Alkalinity 100. Calcium 120. PH 7.0. Stabilizer 50, no copper or iron in water. Pool holds between 12000-13000 gals. When I shock used chlorine shock predisolved.

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Brown stains on bottom (pebble tec)

Postby tired pool owner » Wed 27 May, 2009 10:10

Pool User wrote:Swimming Pool Pro, Chlorine is added through skimmer(3'Tabs) Total chlorine and Free is 5.0,Alkalinity 100. Calcium 120. PH 7.0. Stabilizer 50, no copper or iron in water. Pool holds between 12000-13000 gals. When I shock used chlorine shock predisolved.

brown stains on bottom (pebble tec)

Postby Susan » Mon 17 Aug, 2009 16:44

:( I hate my pool. Wish the heck I would never had spent the money....nothing but trouble. always have a stain here...algae there....lizards fall in....leaves blow in. I want to cover it up with dirt and mow the yard like I used to.

brown stains on bottom (pebble tec)

Postby bagman » Sun 11 Jul, 2010 11:09

Brown cicular stains about a quarter to half doller size. Anyone know what the cause is? Gunite pool 18x36 9' deepth. Spots are mostly in shollow end to half way down. Nine in total. PH is 8.1 trying to lower. Pool is only three years old.
Spots on pebble tec

brown stains on bottom (pebble tec)

Postby Spots on pebble tec » Mon 30 Aug, 2010 03:47

Black algae will appear as dark black or blue/green spots, usually the size of a pencil eraser tip. Their roots extend into the plaster or tile grout, and unless the roots are destroyed completely, a new head will grow back in the same place. The heads also contain protective layers to keep cell destroying chemicals from entering the organism. Like yellow algae, black strains can bloom even in the presence of normal sanitizing levels and proper filtration.

For algae which is not suspended, but only clinging to the walls, follow the same advice above, first shock with brushing, then add an algaecide, brush again, vacuum to waste (preferred) or vacuum and then backwash the filter. Use of a steel bristled brush is recommended for algae on plaster pools (use nylon brush on vinyl). Filter, Filter, Filter!

For black algae, the brushing part is very important. You must tear through the protective layers so the chemicals can destroy the plant from the inside out. Pumice stones work well to knock off the heads of black algae. (Don't forget to vacuum them up later, and backwash them out of the filter ASAP). Also effective on the black algae nodules is sprinkling granular trichlor over the spots (of course if they're on the wall this is next to impossible). Rubbing the spots on the walls with a trichlor tablet or stick can also be effective to knock off the heads and get trichlor directly to the roots. Follow up with a dose of copper algaecide, or high strength polymers. Simazine, an herbicide, was a very effective black algae treatment, but is no longer available in America.
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brown stains on bottom (pebble tec)

Postby chem geek » Mon 30 Aug, 2010 11:18

First of all, with a pH of 8.1, it is very possible that the spots are metal stains and note that they are brown and not black. If lowering the pH and rubbing a vitamin C tablet on the stain fades it, then it is likely a metal stain, probably iron. If instead this doesn't fade the stain but a Trichlor puck does, then it's organic and probably black algae. Also, if one scrapes off some of the black algae and smears it on a white piece of paper, it will look dark green.

Spots on pebble tec wrote:Like yellow algae, black strains can bloom even in the presence of normal sanitizing levels and proper filtration.
Follow up with a dose of copper algaecide, or high strength polymers.

Black algae develops when the Free Chlorine (FC) level is too low relative to the Cyanuric Acid (CYA) level for an extended period of time. It grows slowly, unlike green or yellow/mustard algae. As noted in the previous post, the key is to brush vigorously to knock off the heads to expose lower depths to shock levels of chlorine. Use the Chlorine / CYA Chart to determine the shock level which is an FC that is around 40% of the CYA level. Obviously, if the CYA level is very high, it is more practical to lower the CYA level by doing a partial drain/refill (or continuous drain/refill) to dilute the water first since you don't want a high CYA if you want to prevent algae in the future and a lower CYA level will not need as high an FC for shock level. See Defeating Algae for more info.

It is unwise to use a copper-based algaecide (or to use metal ion systems) in a plaster pool due to the risk for staining. Plaster surfaces tend to be alkaline and can stain easily if the pH gets too high. The level of copper needed to kill algae is close to that which causes staining unless the pH is kept low. Chlorine alone will kill algae and will also prevent it from growing in the first place as shown in the chart linked to above. An FC that is around 7.5% of the CYA level in manually dosed pool will prevent algae growth (around 5% for saltwater chlorine generator pools). CYA significantly reduces the active chlorine (hypochlorous acid) concentration by a huge amount and is known science since at least 1974 as described in this scientific paper. "Normal sanitizing levels" as defined by the pool industry are typically 1-3 ppm FC independent of the CYA level which of course is insufficient to kill algae faster than it can grow when the CYA climbs due to the continued use of stabilized chlorine product. The following are chemical facts:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

So even with a very low 1 ppm FC per day chlorine usage (usually it's higher than that in pools exposed to direct sunlight), the CYA level from Trichlor tabs/pucks will increase by over 100 ppm in 6 months if there is no water dilution. If one has a cartridge filter, then there is no backwashing and if one has no summer rains with rain overflow then one can have the CYA level get too high.
James Watson

brown stains on bottom (pebble tec)

Postby James Watson » Mon 30 Aug, 2010 16:09

Brown spots that are well defined and circular (or other well defined shape) are typically from something metal sitting on the plaster. Typical things that cause these types of stains are lawn and patio furniture where the metal feet sit on the bottom. Sometimes the wind blows the furniture in, and sometimes people throw the furniture in to clean it or protect it from a storm.

Other typical things include washers (like those used on nuts and bolts) etc.

Stains from iron in the general water will typically be more diffuse and splotchy with no discernable shape.

Sometimes iron stains can form in small circles if the plaster has spot etching. The iron tends to concentrate on the etched spots. If the spots are rougher than the surrounding plaster, then it is most likely spot etching. If the brown spots are on plaster that is the same texture as the surrounding plaster, then it is due to a metal item sitting on the plaster.

As chem geek noted, try ascorbic acid (vitamin C) to see if the stains fade.

brown stains on bottom (pebble tec)

Postby kenny123 » Sat 29 Dec, 2012 14:15

All pool finishes will stain in time. If you keep the water balanced it only takes longer for this to happen. Out of balance pool water pool can cause the pool finish to discolor or stain quicker. To prevent pool staining it's important to check the pool water at least weekly and keep the water balanced. Your local pool store can help with this. Metals get into the pool from many sources and will attach to the finish and over time discolor. There are products available to either keep the metals suspended in the water or allow the filter to remove them. They are called sequestering agents and are available at your local pool store. They come as a liquid in a quart bottle and can be poured directly into the pool water. Most pools need about 1 quart/month for a pool size of 10,000 to 15,000 gal. Some brands such as "Jack's Magic” (a company that specializes in pool stains and has a wed site) are testable; they get used up over time depending on how many metals are in the pool water. Anything you can do to keep dirt, a main source of metals, out of the pool water will help. If you have a pool stain or discoloration you first need to test the discoloration to see if it is a metal stain or something else. NEVER NEVER guess at what it is, throw something in the pool or have the pool drained to have the finish cleaned (acid washed) without testing the stain first. A lot of stains look the same but are different in nature. Some are algae, some are from metals getting in the water, some can be dirt stains and some can be from the plaster itself or with vinyl pools, black fungal bleed thru as an example. Most of these all take a different product and or procedure to resolve them. For metal or dirt stains your local pool store should have or can get for you an inexpensive stain I.D. kit to test the stain. This will let you know if it is a surface stain and what product can be used to remove it. If this test does not work, you probably do not have a metal or dirt stain. At this point you should call in an expert to help identify what the discoloration is, how to get rid of it and how to prevent it from coming back. You may need to check with the finish manufacture to find an expert. Most local pool stores or people in the pool industry do not have this kind of expertise.

brown stains on bottom (pebble tec)

Postby jrpdante7 » Thu 16 May, 2013 01:06

I am reading over some of these reply s and was wondering if you have a pool with a vinyl liner. If so, the stains could actually be small amounts of ground water that push up through the concrete bottom and become trapped between the liner and the bottom of the pool. The water then leeches into the concrete and forms rust colored stains from the minerals in the ground water. The stains look as tho they are on the water side of your pool but they actually under the liner. The liner is transparent enough that these stains can be seen. I have recently removed my liner to find this to be the cause. As a result, I have sealed the small leech holes with hydraulic cement and it seems to have stopped the ground water. I am then going to seal the concrete with a white based sealer to insure a uniform color on the bottom.....Just an observation from ten years of having my vinyl liner pool and a lot of trial and error....
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brown stains on bottom (pebble tec)

Postby Aqua team hunger force » Sat 07 Sep, 2013 15:10

What happened was the sand shifted and a grain pierced the liner. The Ph went up causing the metal frame to bleed through or stain the area look in the middle of the stain will bet you see a pin hole.
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Postby newpoolontheblock » Wed 30 Dec, 2015 16:11

Weeniehead wrote:I work for a major pool builder and see this issue every day.

What you are describing is what is known as Dirt Scale.

Basically, a thin layer of calcium buildup has trapped the dirt on the surface of the pool. This is the reason you cannot brush it away. It's sort of like painting a coat of polyurethane over a spot of dirt on the wall. Unless you break down that calcium buildup, that dirt is not going to go away.

Most people only pay attention to how clear the water looks. If the water is clear, the water chemistry is good. It's not as simple as that, but it is easy.

If you don't already have one, get to your pool supply store and purchase a chemical test kit. The test strips will work, but if you want a more accurate test result, get a kit that includes the drops.

Once you have a test kit, you will want to test the water at least 2-3 times a week. The most important things to pay attention to are PH, Total Alkalinity and Hardness. It is important to keep the PH around 7.2-7.6 to avoid the buildup your seeing.

BTW, there is a very simply way to get rid of that scale. It will take some time but it will work if you put the time and effort into it. All you need to do is drop your PH level to about 6.8-7.0 and BRUSH BRUSH BRUSH. Test the water even more frequently during the process. Like I said, you probably won't notice any improvement right away, but over the course of a few weeks, it will start to fade away.

If you want a "quick fix", you can contact a pool service company (one who knows what they are doing) and they can drain the pool and do an acid wash which will do the same thing as the first method, only faster.

Good Luck!

My pool is only two months old. I noticed these same brown stains on my pebble sheen surface the day after adding hardener to the water (as instructed by the pool experts at Leslie's). Could the calcium in the hardener have built up or left a residue and caused these brown stains? If so, will this method you describe in your post work on getting them off?
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Re: brown stains on bottom (pebble tec)

Postby Larry » Mon 04 Jan, 2016 09:29

The pool store recommended adding a hardener because they probably measured the water and found it too low.

If the pH or alkalinity were very high when you added the hardener it could have resulted in scale forming very quickly. Scale that rapidly appears is often discolored.

First of all we need to know why the scale formed, so we need to know the test results for the following:
  • pH
  • total alkalinity
  • calcium hardness (or total hardness)
  • free chlorine
and also what chemicals were added prior to the stains appearing.

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Re: brown stains on bottom (pebble tec)

Postby Little Bird » Fri 05 Aug, 2016 17:04

I have been working with these issues for 12 years. I read some comments and they all make sense. However, some problems are bigger than what we are talking about. Usually, it just happens to pools that you really can't control the PH. Then you ask yourselves: how come? If I have everything under control (PH, chlorine, alkalinity, stabilizer, calcium balanced), it is impossible to not keep them at the right or acceptabke level, RIGHT???
WRONG. Did you consider leaks? Well water? Bad or no circulation???
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Re: brown stains on bottom (pebble tec)

Postby paulbest » Sun 07 Aug, 2016 02:15

Swimming pool stains can be caused by metals in the pool water, rust coming through the wall or by any organic material. The first clue to identifying the type of pool stain is the color of the stain.

A greenish-brown colored pool stain is generally due to something organic such as leaves or mud sitting in the bottom of the pool. reddish-brown or rust like appearance are likely caused by metals.

To prevent pool stains, keep pH and alkalinity balanced, to avoid mineral stains (from low levels), and scaling stains (from high levels).

For algae prevention, proper pool pH and alkalinity will allow your sanitizer to work more effectively. Remember, Pool Stains and Pool Algae don’t just happen, they need certain water conditions to occur. Take care of your pool’s pH and alkalinity first and problems with staining or algae will be easier to manage.

Re: rust stains

Postby tessa » Fri 12 Aug, 2016 18:25

Cheryl wrote:Could be algae - need to get an algaecide and liquid chlorine, brush the pool real good, put algaecide and liquid chlorine in then let fi;ter run until pool water is clear.

Cheryl 8)

Our pool was just re-plasterd and tiled this year, we have the same problem, never had this before...Pool water tests well, we shocked it beginning of the week, retested good, PH is a tad low, so perhaps we will try brushing the crap out of it....Sure as heck do not want to mess up this new plaster......its annoying at best

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