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.

tired pool owner

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.
chem geek
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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....
Aqua team hunger force

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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