Determining need for Sequestrant post AA treatment

[Caracat]

Hey all, I had a lot of ugly iron stains and performed an ascorbic acid treatment in September 2020 in accordance with a couple TFP threads. Took a while, but it worked great! I used Jack's Pink Stuff as my sequestering agent. I was reluctant to spend $100 on a Sequestrant test kit, so I didn't, nor did I continue using the Pink Stuff after the AA treatment. As of July 2021 my pool still looks great, no stains or issues. I do however, have a bottle and a half of Pink Stuff left over.

My question is- do I need to bother using it if I'm not seeing new stains? (& risk potential phosphate buildup with regular use)

I realize that the metals that caused the stains didn't magically disappear, but we have had tons of rain this year, to the point that my CYA fell by 1/2 and my CH by 1/3 since about February. Is it possible that the metals have been similarly diluted? Is there a magic number of sorts to determine when iron content is high enough to warrant using a Sequestrant as a preventative?

This is an old pool (1961). Plaster is decent, not great. You can clearly see many rebar spots on the bottom of the pool. (Could this be how iron is getting into the water?) Naturally, I'd rather buy the $100 kit and use a sequestrant regularly than fork out big bucks for a replaster. Even better- to do none fo the above if it's not really necessary. What would you recommend?

Thanks!
Caracat

 

[mknauss]

Houston fill water has iron in it. Rain does not. So displacing that much of your pool volume with rain has diluted the iron levels.

If you start to use tap water as fill water, I would suggest using sequestrant or being ready to filter out the iron before it stains.

The exposed rebar may be adding to the problem. I assume you have rust stains were it is exposed.

 

[JoyfulNoise]

The only long term fix is a full chip out of the old plaster, fix the rebar, and then replaster the pool. You might consider, if possible, adding a whole-house iron filter to your municipal supply and attach it to the auto fill line or run an outdoor spigot with treated water. Obviously that’s a lot of expense and, if this is not your “forever” home, then it’s not worth doing any of it. AA treatments with maintenance dosing of the Pink Stuff will hold the iron staining to a minimum. Then “the next guy” that owns the house can deal with the pool renovation.