Removing Fe stains on a vinyl pool

[steve53]

I have an in-ground 30,000 gallon pool that has gradually been accumulating reddish iron stains over the past four years- when I put a new liner in.

To make a long story short, I think I will "shock" it with citric acid. I have read that the effect is almost overnight. I am aware that the pH has to be corrected after the shock before swimming in it.

Has anyone done this? Does the vinyl require a good brushing before restoring the pH?

What sort of citric acid should I use? I bought a gallon of concentrated citric acid cleaner at the local hardware store and used it up cleaning my filter cartridges. Yes, I am a cheap guy and want to stay away from pool suppliers. So what type should I buy, and how much of it should I use?

For increasing the pH, I have been using plain A&H baking soda. Any problem with that?

First post and thanks in advance!

 

[tim5055]

Welcome to TFP!!

Well, check out this article. Ascorbic Treatment to rid Pool of metal stains

- - - Updated - - -

For increasing the pH, I have been using plain A&H baking soda. Any problem with that?

Baking soda is better for raising TA, not pH. Pool School explains this in detail, but to quote regarding pH:

Raising PH

PH can be raised in three ways: borax, soda ash, and aeration. Borax is usually the best choice. Borax raises the PH and also raises the TA level just a little. If your TA level is low soda ash will raise both the PH and TA levels. If your TA level is high, aeration is best as it will not raise the TA level at all. However, aeration is rather slow compared to the other two.

Borax is available as 20 Mule Team® Borax Natural Laundry Booster. It is sold in the laundry detergent section of most larger grocery stores and some big box stores. Borax is best added by pre-dissolving it in a bucket of water and then pouring that slowly in front of a return.

Soda ash is available as ARM & HAMMER® Super Washing Soda Detergent Booster. Do not confuse this with ARM & HAMMER® laundry detergent! It is sold in the laundry detergent section of most larger grocery stores and some big box stores. It is also sold by pool stores under various names, including PH Increaser, PH Up, Balance Pak 200, etc. Soda ash is best added by pre-dissolving it in a bucket of water and then pouring that slowly in front of a return.

Aeration can be provided by a SWG, spa jets, waterfall, fountain, return pointed up so it breaks the surface, air compressor, kids splashing, rain, etc. It can take some time for aeration to raise the PH. The higher your TA level, the faster aeration will work.

There is a link for Pool School at the top of every page. Lots of good information there.

 

[JoyfulNoise]

@Tim5055 pointed you to the correct article for iron stain removal but I just thought I'd chime in and point out that you should use ascorbic acid NOT citric acid. They are often confused with one another but they are not the same thing. While citric acid will work, you have to use almost twice as much to get the same effect as ascorbic acid.

 

[Isaac-1]

If your water is high in iron you will also need to add a sequesterant (jack's magic brand is often suggested here) to keep the stains from coming back. Alternatively if the stains are caused by a specific point source you may be ok with just the ascorbic acid treatment. I had to do one a year or two ago after getting lots of rust and steel bits in my pool thanks to a metal roof replacement.

 

[steve53]

Thanks.

The TA and pH seemed to normalize nicely when I put the baking soda in- about four pounds total.

 

[tim5055]

Thanks.

The TA and pH seemed to normalize nicely when I put the baking soda in- about four pounds total.

What test kit are you using?

 

[steve53]

I am using the test strips. Not a kit, I suppose *hangs head in shame*

Just bought some citric acid online:

[SIZE=-1]Citric Acid, 10 lb - FREE SHIPPING, Anhydrous, Fine Granular White Crystals, High Purity, Food Grade, FCC/USP [/SIZE][SIZE=-1]I am letting my chlorine gradually fade away and then I will use the citric acid- should be in a few days. I am figuring it should take about 6 pounds in total? And do I understand correctly that the filter should be bypassed when the acid is added- keeping the pump on? [/SIZE]

[SIZE=-1]1[/SIZE]

[SIZE=-1] 10caf[/SIZE]

[SIZE=-1] Free Shipping Domestic Only [/SIZE]

[SIZE=-1]$24.95[/SIZE]

[SIZE=-1] [/SIZE]