Iron and Chlorine

[arf1225]

Hi All,
Last summer, we moved to a new house with a 36,000 gallon gunite in ground pool. The water in it was fine last season and we didn't have any chemistry problems. We DID have major cracks that were causing water leakage, and were "fixed" this spring. The company chiseled them down, patched with hydraulic cement, and were also going to re-plaster, but they were so big that they told us to wait a season on the re-plastering to make sure the cracks/leakage were actually fixed. This has been a longer than it should have been process, but we are finally at the opening stage for the season.

We have iron in our water, and of course we used it to fill the pool, not realizing it until we had already filled it. I am ready to fire up the filter today and get everything running. My main question is, do I get the Jack's Magic and use it PRIOR to balancing and chlorinating, or do I use it after balancing and chlorinating? I use the BBB method, and just want to go about this the proper way from the beginning, if I can. Also, is there a place besides a pool store that will test water for iron? Or should I just bite the bullet and get my own iron testing kit? (I have a good Taylor test kit for other chemistry). With a pool this big, I'd like to keep the costs of sequesterant down as low as possible, so I imagine I should know how much I need in the water based on the amount of iron or other metals present.

Our former home had a nice, little 18,000k IG fiberglass pool with a simple setup, with which I was familiar and which I could get under control easily if things went sideways for whatever reason. This pool intimidates the heck out of me. It is HUGE, the set up is very different, the filter is DE instead of sand, the water here is different...I'm just a bit skittish. Any help would be appreciated.

 

[duraleigh]

Welcome to the forum. Let's discuss your iron concerns. You ask about the best way to test for iron but don't tell us how you confirmed you have iron. How did you know that?

 

[arf1225]

Ahh, yes. Next door neighbor with IG pool confirmed. Also, the tea brown color of the water while/after filling. I'm going to bring it to a pool store today for testing. Found one that tests for iron and iron levels.

 

[chem geek]

With a large pool it's going to cost you one way or another to keep the iron from staining. Sequestrant is an option but as you point out for your larger pool the maintenance dose might be pricey. However, even doing a water change with water free of iron (i.e. trucked in) may be expensive depending on where you live. Options for physically removing the iron such as the CuLator are not cheap but they depend on the amount of iron you have. Metal Magic to catch the iron in the filter may also not be cheap. The least expensive removal approach is to use pH Up in the skimmer to precipitate iron in the filter, but this is also the trickiest method so not consistently reliable.

If your water is actually colored and looks like it might have visible particles, not clear color, then you can try using skimmer socks or batting material in the skimmer to try and filter out these particles. The good news with iron is that when oxidized by chlorine it isn't very soluble so should be filtrable. If your filter is a sand filter, then if the iron particles are very small then DE might help. If you are able to filter out the particles and slowly increase the pH to continue to create more particles (and hopefully not have them stain), then that may at least get the bulk of the iron out of the water such that any other methods become less expensive because there will be less iron to sequester or remove.