Water turned yellow-ish after adding CYA?

[volcano]

Hi all-- in the process of filling our 10'x30" AG Intex. Filling gradually so we don't strain our well. Now on day two of filling, pool has about 12" of water in it, and I've been adding bleach to keep Cl levels at >5 ppm during the filling process (calculating with PoolMath, checking that it's >5 ppm using K-1003 kit).

We left town yesterday mid-day so I increased the Cl up to 20 ppm before we left; it was back to 0 ppm by this afternoon (super sunny day, pool water at 92˚F!) so I immediately bumped it up to 20 ppm when we got home today. An hour later, I added some CYA (Clorox-brand dry stuff) to bring CYA to 30 ppm, and pool water suddenly went from sparkling clear to sparking yellow-ish (green-ish?).

1. Our well water goes through a Hague 800 iron filter, so shouldn't have any iron in there.
2. Although Cl was briefly at 0 ppm, it couldn't have been for more than a few hours. It was at 20 ppm 24 hours ago. Can't really envision an scenario in which algae colonized a new fill that quickly? Pool was covered with an Intex solar cover.
3. Color change didn't occur until the CYA was added.
4. Right after water changed color, I checked Cl again and it was at 2 ppm according to K-1003. Just added bleach to bring it back to 10 ppm.
5. Any ideas? Thanks!

Thanks!

 

[duraleigh]

I am not familiar with the principle of that Hague filter but the condition you describe is from iron in your water. It is the addition of chlorine that precipitates into a solid giving the water a yellowish, sometimes greenish tint. Clear water but tinted, right?

I have no idea why it appeared that the CYA caused it but I am sure it was caused by the addition of chlorine.

Can you post current test results for

pH
FC
CC
TA
CYA
CH

 

[volcano]

If it were iron then it should have precipitated when the Cl concentration was higher, though-- it's been as high as 20ppm. Color change didn't occur until the CYA was added-- the lower pH should make the iron more likely to be *in* solution, which is why I was surprised that it appeared after the CYA was added. To be fair, though, it isn't precipitated, it's clear but yellowish tinted.

Hmm. The Hague filter has a capacity of ~1000 gallons before it needs to be regenerated-- it typically regenerates every third day. I just checked now and it's scheduled to regenerate tonight, which means we've certainly exceeded 1000 gallons (we've added 880 gal to the pool, plus normal household water usage) since the last regeneration cycle.

I have a the K-1003 test kit, so I can only give you the following:
pH: 7.5
Cl: 5 ppm
CYA (calculated): 20 ppm
Oh I guess I can give you TA, too, but I'll report back in a bit with that.

So if it IS iron, do we add a sequestrant? Lower the pH so it precipitates out, then vacuum it off the bottom? Hope the filter will remove enough of it (this seems unlikely for a standard cartridge filter)?

Thanks!

- - - Updated - - -

Also, just got the water level high enough that we can start running the filter (the pool return port is above the water, but both strainer ports are below the waterline now). The Hague will cycle tonight and I'll add more (Fe-free) water tomorrow.

 

[volcano]

Okay yep, it's definitely iron-- have some deposited on the walls now. I put a paper towel over the strainer port for less than a minute and it's stained orange. Which bodes well for some of the iron being removed by the filter, though, so I guess that's a net positive...

 

[duraleigh]

Your filter will remove the visible particles (that includes those particles causing the tinted color) so your water should slowly go back to clear.

To be fair, though, it isn't precipitated, it's clear but yellowish tinted.

That's precipitated iron. If it doesn't precipitate, you can not see it and it will not tint your water.

Once the pool is filled, it sounds like your Hague will be able to supply enough iron free fill water so you should be good to go.

 

[volcano]

That's precipitated iron. If it doesn't precipitate, you can not see it and it will not tint your water.

Aqueous Fe3+ can also produce yellow compounds, I believe. Either way, though, I’ve obviously got iron precipitate as well— glad to hear the filter will likely resolve it. Thanks for your assistance!