Iron and CYA reduction

I am contemplating a water change to reduce excessive CYA levels and also remove iron stains from the sides of my fiberglass pool.

I've read the sticky involving Ascorbic acid treatment with intention to dissolve existing stains then pump my pool while I simultaneously add water from my pond. I'm wondering about the addition of the sequestrant after the stains are dissolved. Since my goal is to remove as much of the water as possible is there any immediate need for HEDP? I can remove / add water at a rate of approx. 1500 gallons per hour and know I am actually only diluting the amount of dissolved metals and CYA.

I intend to run my water replacement scenario for approx 16 hours resulting in 24000 gallons of new water being pushed into a 25,000 gallon pool. I'm assuming there is minimal risk of re-stain during the pumping process since pond water PH checks 7.0 and I have no intention of adding chlorine at any time during the pumping process.

My plan is to add HEDP, chlorine and CYA if needed when the water swap is complete. Assuming my initial dose of ascorbic acid dissolves my stains is there any risk of stains reappearing while the pumping is in process and the ascorbic acid is diluted?

Is there anything else I should be concerned about?

Thanks in advance for any advice!

OK. You'll need to slow down a bit. You wrote, "assuming there is minimal risk of re-stain during the pumping process".

I wouldn't assume that, at all. If you mean, is it possible to fill with water and treat it during the fill so that it won't IMMEDIATELY restain the pool . . . then, yes, that's possible. But if you mean can you assume that the new water won't stain the pool sooner or later . . . absolutely not. From where I sit, that's EXACTLY what I'd assume.

One of the things I've learned from trying to help people with stains is that it is a USELESS effort, unless we FIRST figure out how the stains got there originally and then SECOND have a workable plan to prevent it from reoccurring.

What has happened more often than not, is that people successfully remove the stains . . . for a SHORT WHILE . . . and then they reappear.

So, do you know how the original stains occurred? Do you know if the water you plan to fill the pool with, day-to-day is iron free? Have you tested the pond water (pH, alkalinity and iron)?

And, what is your current CYA level? Why do you think this is a problem?

I've owned my pool for 17 years and it's been mostly stain free until the last couple. I have my gutters arranged to allow for discharge in my pool in attempt to minimize adding my well water which contains some iron. I don't have a heater or any other ferrous metals in the pump / filter system that I am aware of and am pretty confident my source of iron is the well water.

I use the Taylor test kit recommended by this forum and believe my high CYA levels are not desirable based on the information I have learned here. I'm pretty good at keeping my pH, alkalinity and chlorine at the correct levels. My most recent water test (last week) measured normal levels for everything except CYA which was significantly above the highest level on my test kit (I think that's a 150ppm level) CYA has been increasing for the last few years. I also had a pool store test a separate sample for comparison to my Taylor tests and results were very close and everything within recommended levels except for very high CYA and phosphates which were supposedly at 2000ppm.

My water is clear, but the side of my pool where the chlorine rich water from the returns flows along looks like it's been sprayed with light brown paint and extends halfway down the length of my pool. Last summer there were days where the stain was present in the morning but had completely disappeared by noon. This would happen for several mornings in a row until I let chlorine levels drop off. I've never read anything on this site about stains that come and go but mine did last year. Vitamin C tabs take it off, so does Muriatic acid. This summer the stain looks like it's here to stay which is forcing me to take action.

My #1 goal is to eliminate the stains and delay their re-occurrence. I'm certain someday they will reappear. The challenge is how long can I prevent it without making it something I need to think about and act on every day. I read that water replacement is the routine way to drop CYA so I figured trying to dissolve my stains and take some metal out at the same time with a water replacement would be a smart move rather than only attempting to dissolve and manage the stains with sequestering agents. I must be one of the lucky ones considering I've gone along for years with minimal staining and enjoyed a pool that has stayed clean and clear. The last couple of years staining has become troublesome and I'm guessing it's due to continual buildup of metals and maybe CYA and the higher chlorine levels required in conjunction with it.

I plan to sample my water immediately before and a while after adding the ascorbic acid then again after the water swap to see if I've made any progress. Currently my pool water shows shows zero iron or copper (according to the pool store tests) but I believe that's because it's stuck on the pool wall. I agree it would be smart to test the pond water too before using it and will do that shortly. I'm not a chemist but it will be interesting to see if it contains measurable iron because I built it and know it's not spring fed but probably contains phosphates and fertilizer runoff from farming activities. I've never thought about the presence of iron in anything but water pumped out of the ground so I'm learning as I go.

I've tested the pH...it's 7.0 As far as a future plan I want to minimize the use of my well water and think adding some Hedp might help. If I can roll along for a few years with minimal staining until metals increase again and I'm forced to do another water replacement I'm OK with that as part of my management plan. So far I've got about $60 in PVC to hook up my water supply and about $65 in 8lb of ascorbic acid. I live on a farm and can get away with stuff people it the city and suburbs probably can't, like pumping 24,000 gallons of pool water into a hayfield and scaring my fish with a pump running for a couple of days!!! Water replacement from my pond every few years will be very economical for me if it goes as I hope.

I'm not looking for any guarantees but if you think this has some merit and can suggest anything else to consider or watch out for I'm all ears!

I do appreciate your time.

OK.

I don't think your CYA is a problem for the moment. Just stop using trichlor or dichlor, and start using cal hypo or bleach.

If you are still at the same location as when you registered in 2012, the Walmart in Greencastle is stocking it:
https://www.walmart.com/ip/Pool-Esse...iquid/48938023

The only cheaper source of chlorine likely to be available to you is trichlor from Sams Club ($2.10/lb for 90% chlorine . . . but ALSO 50% stabilizer. And yes, those %'s are correct, but no, I'm not going to explain here.)

You'll need to maintain your chlorine level at 5% of your CYA, or around 7 ppm.

Also, you need this: Hach 0.15 ppm - 5 ppm iron test strips That's a direct-to-Hach link. They are available on Amazon, but for TWICE the price.

I suspect you'll find that your pond iron levels are much lower than your house water. Compare pond water with house water BEFORE any softener. Softeners remove iron . . . but pool filling tends to use so much water than the iron 'breaks through'.

If it's as I suspect, you'd be better off filling with the pond, using some sort of semi-permanent arrangement.

BUT . . . if you have a sand filter, AND can purchase and use cal hypo, there's another way.

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Also, you WILL need a Taylor K2006 kit. You are going to have to manage pH and alkalinity better than test strips or dealer testing will allow, and if you use the sand-filter + cal-hypo + my-secret-sauce method of removing iron, you're going to have to monitor calcium levels, as well.

And . . . don't use any more HEDP. Every bit of it turns into ortho-phosphates (AKA algae-food) over time. With PO4 levels of 2 ppm (2,000 ppb) you are ALREADY approaching levels that are associated with uncontrollable mustard algae, once water temperatures rise.

Basically, you need a FULL plan in place, BEFORE you start draining and refilling.

And a final caution: I'm not sure about this, but it SEEMS that once a pool has stained, it is more prone to stain in the future. It might be my imagination, but I don't think so. There are all sorts of chemical reasons why it MIGHT be true, such as tiny remaining bits of iron that give new deposits a 'place to start'. Regardless, this has seemed to be the case on pools I've dealt with.

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