Iron Stain / Ascorbic Acid Frequency

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Hoster

Hoster

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May 27, 2016
183
Berkeley Heights, NJ
Applied / spread ascorbic acid once first two months (of opening). Since then AA treatment almost every week due to brown / iron staining, and wondering what's going on as nothing significantly changed. I even took the pool light out, cleaned out the niche (was pretty dirty and this may be causing some mustard algae which is another story - if you are going to remove your light, please have your vacuum ready-to-go before dead / live algae spreads), and currently soaking screws in vinegar / AA to remove any rust.

FC 1.0 (will increase / go through SLAM then Mustard Algae treatment)
pH 7.0 (had to lower TA and aerating a bit)
TA 75
CH 50 (but vinyl pool)
CYA 70
Borate 40

Not sure why iron staining is occurring so frequently...went through 10lb of AA this season already and looks like another 10lb until closing (mid-Sept??).
I did read on a TFP board that I should not increase FC dramatically once I go through AA treatment so I did so..in fact, was going through the process of slowly increasing FC but this occurred again.


Any insights? (oh...have Culator and poured in 2 qt of Jack's Magic Purple 2 weeks ago)
 
pH, TA can cause the iron to precipitate but to solve your problem you need to find the source of the iron. I think you can get a water report from you city supplier or maybe even ask them for an iron test at your location.

Do you have a whole house softener?
 
Hoskim, what sequestrant are you using when you perform the AA treatments?

I ask because some metal sequestrants don't work well in the "high TDS" environment of swg. For this reason, those on swg should use jacks magic purple, which is specifically formulated to work in a salt pool. Give that a try and be sure you're adding a full start up dose, not a maintenance dose, after your AA treatment.

With respect to the origin of the iron, it is possible that trace amounts are coming from the salt itself...if there are trace amounts from the salt and trace amounts from municipal water, plus the electrolysis process of swg, you have a formula for frequent staining. It will help to control your ph (eg if possible, keep it low ish - eg 7.2-7.4) or at very least not let it get past 7.6.

If you are using and maintaining the right kind of sequestrant, and controlling your ph and still get staining weekly then you'll need to dig a little deeper and get both pool and source water tested for iron, inspect the pool for any corrosion, and consider additional plans such as prefiltering your source water and possibly adding an inline zinc anode if there's corrosion.

But first, lets make sure you're coming out of the AA treatment correctly with sequestrant, and that you're adding maintenance doses and controlling ph.
 
Thanks and that's very insightful. I will try to keep the Ph low. The funny thing is I only used the Purple Stuff and I thought that may be the reason ;-) Being frustrated with the frequency, I recently added a bottle of Kem Tek (still have 1 1/2 bottles of Purple Stuff as well) which seemed to help but not much. In any case, your last sentence of "But first, lets make sure you're coming out of the AA treatment correctly with sequestrant, and that you're adding maintenance doses and controlling ph." makes perfect sense - unfortunately (or fortunately?? ;-) ) we will likely close our pool within next 2-3 weeks.
 

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The reason I ask about the dirt, is I recently found out that in places where the dirt/clay is red, it's usually from iron in the ground. But since you are brown dirt, that's not it.
My exchanger was made of iron and it was rusted. I didn't know that and when I tried to get it going I dumped a couple of pounds of rust into the pool. I cleaned it all out, but the damage was done.
 
The funny thing is that this happened recently. Nothing in june and july
Click to expand...

Have you had your lawn fertilized recently? Fertilizers also contain trace amounts of iron, just so you know. Also, you might want to take a peek inside your heat pump to see if any corrosion has developed...even if its turned off, if there's water running through it and any iron parts it could in theory become a source, in which case an inline zinc anode might help.
 
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