yellowish spots on bottom of the pool

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michmike

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Apr 11, 2011
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Houston, TX, USA
hey guys,

i am not sure if this is the proper subforum to post this, but none of the other forum areas matched perfectly either.
I have some yellowish spots at the bottom of my pool (the walls of the pool are perfect and have no staining) and i was wondering if anyone else has had these in the past and what the best way to treat them is. My plaster is 2 years old and these probably developed over the winter when my pool turned green.

any help is appreciated. i attached some pictures as well.
 

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it is stuck to the surface. no matter how much i brush, it does not seem to get removed (and no clouds when i brush the spots). antyhing i can do with that?
what can cause iron stains so that i can stop doing it right away? I always broadcast my chemicals around the pool surface (or through the skimmer if that is the recommended way based on the product) and i brush the pool right after to mix them properly.

all my chemicals are balanced within range: FC, TA, CYA, CH, etc
 
you might have iron in your fill water- the chemicals you normally use won't add iron, but won't remove it either. I've never had to use sequestrants, so can't advise in detail- and it's possibly something else...
Do you have red stains in the fill tank on your toilet in the house? this is an big indicator of iron in your fill water...
 
Try holding a vitamin C tablet against one of the stained areas for 30 seconds and watch to see if the stain lightens or goes away in the next few minutes. If it improves significantly it is iron and can be treated with an ascorbic acid treatment.
 
hi guys,
so i looked into our toilet fill tank and we do have some red stains in it. In addition, i held a vitamin c tablet and i rubbed it against the stain and it seems to have removed.
Now, i was reading this article, ascorbic-treatment-to-rid-pool-of-metal-stains-t2298.html, and the process takes 1-2 weeks. I have lots of travel plans this summer and it makes it hard for me to do this and be on top of it.
I was wondering if any knew what the risks are of waiting until September to do this treatment. Will there be damage to plaster?

Also, a friend told me this could be because of the heating element in my pool heater (that i have not used in 5 years), so the stains could be copper.
 
Since the vitamin C cleared up the stains they are almost certainly iron and not related to the pool heater.

There is no harm to leaving the stains alone for a while. They just won't look very good. Otherwise dealing with them later will be the same as dealing with them now.
 
thanks Jason. I was reading a lot on these stains this morning and i found your posts on other threads very useful.
Would you say that this whole process can be done in 2-3 days or would it take more time?

I definetely got my shopping list together and plan to stop by the pool store. if there is another big brand place that carries these stuff it would be good to know since it would be faster than getting them online and save on shipping.
-need 2-4lb of citric acid (to remove the stains)
-need 32oz of polyquat 60 (to prevent algae with 0 chlorine)
-need 48oz of Jacks Purple Stuff (sequestering agent)

From Jason's comments on other threads i found these two tidbits to be very useful.
--> Sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are the most effective
--> When there is iron in the water, low PH (say around 7.0 to 7.3) tends to prevent staining while high PH (say around 7.8 to 8.2) tends to cause staining. High FC levels also tend to cause staining.
 

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michmike said:
anyone also know how long it would take for chlorine to come down to 0 from a FC 6 after i shutdown my SWG?
Click to expand...
If you want to speed up the process, you can neutralize the chlorine with citric acid. About 2 pounds of citric acid will quickly lower the chlorine from 6 to 0 in your pool.
 
quick question Jason. I am planning to add borates (using borax and muriatic acid) and follow the instructions this weekend. is it a good idea to add the borates and follow that treatment 1 week prior to trying to remove the iron stains?
so this sunday i am adding borates and next saturday i will attempt to remove the stains
 
The keys to avoiding algae are to make sure you don't have algae to start with, use a large dose of polyquat algaecide, and don't take too long with FC at zero. Even if you do it perfectly you sometimes still get algae, but done carefully your odds are fairly good for not getting algae.
 
madwill, that's kind of the perspective i had as well. that the borates will help me avoid algae in addition to poly 60. i had really big problems with Algae this year, so i am not looking forward to revisiting that. I should mention i am algae-free right now. crystal clear water :)

Jason, thanks for confirming this. glad i asked this because my original plan was to fix the stains and then borates.

Does anyone know how long poly 60 lasts? i found poly 60 [oxyethylene (dimethyliminio) ethylene (dimethyliminio) ethylene dichloride] which is the same as polyquat 60, and 24oz treats 15k gallons it says, but not sure for how long. I will probably drop 32oz in my pool right when i stop using my SWG (and within 4 days hopefully my FC will be 0 and i can do the stain removal). i am also ensuring i got 0 phosphates so algae have nothing to eat (i had a bottle of phosphree, so i might as well use it)
 
It is very difficult to predict how long the polyquat will last. It normally stays in the water until it gets used up, which can happen quickly or slowly depending on how much contamination/algae shows up for it to deal with.
 

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