Rusty Iron Bolt Stain

by Eddie

I have a dark brown iron stain from a rusty bolt that the kids threw in my cement pool. The local pool place here told me that I could put some PH-DOWN into a sock and place it over the stain to remove it. Well, it didn't work and only created a ten foot light colored path from the stain downward toward the lower portion of my pool as the PH-DOWN filtered thru the sock. Now this path seems to collect green algae faster and before other areas of my pool. PLEASE give me some answers to remove these stains.

Thanks for the question Eddie

The pool store employee was 1/2 right when he said you needed a sock. But he was wrong with the product to put in it. You need to get ascorbic acid which is nothing more than crushed up Vitamin C. pH Down, and I'll assume it was granular acid (sodium bisulfate) only reduces the pH and TA. Being that it's acid, it may have bleached out that section of your pool.

Take the ascorbic acid and place it in a sock on the affected area and leave it for a couple of minutes, then rub the area well. Keep doing this until the stain is gone. There are many YouTube videos on how to remove small metal stains and they all use ascorbic acid with this technique, or something very close.

There are mainly 3 kinds of stains; organic, metal, and chemical. Organic and metal are fairly easy to remove. Chemical stains such as yours are a bit different. That's because the area has been effected with a concentrated amount of chemicals. This causes a bleached out area. For vinyl pools there's nothing you can do about it. The affected area may become weaker and puckered up. For plaster pools you may need to drain the water and sand that area down until the color is uniform with the adjacent areas.

Sorry to be the bearer of bad news but if the pool store employee would have simply told you about ascorbic acid you wouldn't have this issue.

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Black & Splotchy Stain On Pool Surface After Shocking

by Ronnie

My pool has a black film and splotchy stain in gunnite after superchlorination with granular chlorine.

I put clarifier in the pool 36 hours ago and a light dose of green algaecide 12 hours ago.

The stain will not scrub off with brush. How can I remove the stain?

Thanks for the question Ronnie

I'd like to have your complete chemical readings:

Chlorine, CYA (cyanuric acid/stabilizer), pH, Alkalinity, Calcium Hardness, and Metals (iron and copper).
It makes troubleshooting much easier and the process of clearing up your pool will go much faster. You can get this done at your local pool store.

Black spots or marks after a shock may indicate a high metal content or black algae which is common with gunite and plaster pools. I would probably say it's metal, but without a definite cause or pictures it's hard to tell right now. If it's not slimy but dry, powdery, adheres to pool surface and difficult to brush off, it's more than likely metal stains. Oxidized copper can cause black stains and sometimes copper can create a dark red-brown stain.

The first step is to identify the stain and see what will remove it. It's also not a good thing if you have a heater and the copper is coming from your heat exchanger. Your pH might have been too low for too long. If you do treat the pool for stains you will have to bypass the heater. A copper level of 0.0 - 0.1 will not normally cause any problems, but 0.3 or higher and you may need to treat it.

You can test the stain with some ascorbic acid (crushed vitamin C tablets) wrapped in a sock. Place the sock on the stain. If it goes away when you rub, it's probably copper, but if it has no effect then it isn't copper. Here's a post and directions for the ascorbic acid treatment:

Brown Algae Won't Come Off Of A Vinyl Liner

If you have hard water, you'll want to shock and weekly use liquid chlorine as chlorine granules have calcium in them which will increase the hardness of the water. Granules also have a pH of 12 which will dramatically increase the pH after a good shock.

I'd encourage you to watch the clarifers. Although it sounds nice to maybe have a clear pool from magic in a bottle, it doesn't address the reason the pool was cloudy in the first place. If the issue is not resolved you're going to use another bottle, then another, and so on. This keeps the chemical companies happy with more of your money. I want you to keep more of it.

Check the kind of algaecide you're using. Be sure it's a quality Polyquat 60. Many cheaper and less expensive algaecides have copper in them. For pools with high metals, you're just adding to the problem. Algaecides are good for limited use or for pool owners that can't test the water weekly as a backup. A properly balanced pool should not need an algaecide.

If you do have a high metal count, then you're going to need a good metal sequestrant. Metal sequestrants that are based on HEDP, phosphonic acid or something similar are the most effective. Jack's Magic Blue, Purple, and Pink Pink Stuff, Metal Magic, Metal Free, & Metal Klear are very good.

A metal sequestrant does not remove metal from pool water. It holds it in solution until it can get filtered. Then you backwash the metal out. Because metal sequestrants break down over time and get filtered and backwashed out, you will need to add a bottle once per week.

Try the ascorbic acid test and get back to me with the chemical readings and we can go from there.

If you need immediate assistance (within 24 hrs) or for emergency personal assistance, you can make a donation of your choice and I'll answer your questions by phone.

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Hope this helps and have a great Summer.


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