Need help identifying stains

[katwar]

Bought this house two years ago. Re-plastered pool at that time. Converted over to using liquid bleach sanitizing program last summer thanks to wonderful folks here. In Houston and pool is open all year. Pool has never been used since re-plaster (I know, I know - long story). Have been noticing what "looks" like algae where rounded half-circle steps meet pool wall and on plaster where upper tile meets plaster, and a few other areas on sidewalls. None of the floor of pool has these discolorations.

Yellowish-greenish-brownish stains that are similar in appearance to mustard algae (kind of). Stains do not brush off whatsoever. Have done two overnight chlorine tests with zero chlorine loss. Ph, FC, TC, CH, etc have been kept at near perfect levels. CYA is a bit high at 70. Did a 60% drain last year to get CYA down out of the ozone (100+ reading). Keep inline chlorinator with pucks on a 1 out of 5 setting (very lowest setting) to supplement bleach just a smidge.

I don't think these stains are organic because of their locations. I do not have well water. I use the Taylor-2006 test kit. Have not tested water for minerals. I have attached a couple of photos and have circled the areas where the majority of these stains are. I don't intend for you to be able to see the stains in these pics per se, just the geographical locations in the pool. Although the arrow does point to one stain that might be visible to you. Stains have been there since last September but then were barely visible to me. They have become increasingly obvious over the winter and are now hugely noticeable. Same areas of the pool all this time. No new or additional stains since these specific ones started last year.

 

[YippeeSkippy]

We need hard fast test results please! Not just "near perfect"...ok?

Pucks are still raising your CYA level....just slower. So you might need to consider ditching them for routine use.

THose areas look like low circulation spots. Do you brush your pool routinely? That helps disrupt anything growing or especially hiding under biofilm and get it into circulation with the chlorine and the filter.

Yippee

 

[jblizzle]

I am curious about your CH level and the pH you maintained over the winter.

 

[katwar]

Thanks YippeeSkippy. I said "near perfect" only to indicate that there was never a period where my chemistry got out of whack that may have attributed to the stains. I keep my FC between 7 and 8. Higher than normal but because of CYA levels felt I needed to offset it by keeping FC higher. CC is 0. pH is always right at 7.5. TA at 90. CH usually 300, sometimes 330. Did I leave anything out?

 

[duraleigh]

Have you placed a puck directly on the stain and held it for a minute or two? If it's an organic stain, the puck will lighten it.

 

[katwar]

And yes, I understand about even a small amount of the pucks raising the CYA. I have a HUGE baby frog season in my pool. I can't stand seeing them die such painful deaths in the chlorine. I have four frog logs but it doesn't take long in that water. I've saved as many as I can by doing rinses on them. So tried to find a sweet spot where the bleach would be added at the time of day that is past when the babies typically jump in and where the pucks could offset the quantity of chlorine used to reduce the death count. I have no issue with having to do a partial drain again if it comes to that. But slower CYA increases are better than quick increases. And those increases came pretty quickly when I used nothing but pucks and granular shock Killing all the frogs instantly and daily is not an option for me. So 80% liquid chlorine and 20% pucks is my compromise....LOL.

- - - Updated - - -

Duraleigh, no, most of the most obvious stains would require my head being under the water that length of time in order to hold the puck on the stain. But I could try and do it on one of the smaller areas where the plaster meets the tile around the edges. I'll go try that right now as a matter of fact. Standby.

 

[katwar]

I'm really really surprised, but the puck did indeed lighten it a bit. Tried on two different areas and both are def lighter. Not gone but lighter. Surprised because very few leaves, etc over the winter and such odd areas since it is on the sides and not bottom areas. And while I was standing in the pool and had my eyes a little closer to everything, I noticed the discoloration covers a lot more area than I first thought. So what does this mean and what do I need to do to treat it?

 

[katwar]

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