Light Blue Flakes

[Geckoeyes]

Hello TFP. I usually find what I need by searching but I haven't had luck on this issue. My pool is on 3rd season. 1st season was pool company controlled and last two have been TFP system by me. The last two weeks I have been vacuuming up these light blue flakes (first picture). Pool is always crystal clear but I do 8oz maintenance doses of Metal Magic to remove iron stains. Heater has been set at 86F all summer and runs just a little each day. I did the Muriatic acid test and the flakes turn yellow and slowly dissolve (second pic) but no fizz. Is this phosphates from the metal magic? Is my heater ok? Should I be concerned or just keep with the program? Thanks for your help.



These test numbers have been consistent all summer:
FC 4.0
PH 7.4
TA 75
CH 300
CYA 40
CSI -0.23

 

[JamesW]

The color looks like a copper compound. What's the worst that the chemistry ever got?

 

[Geckoeyes]

Thanks for the response. I don't know how the chemistry was during the install year while I trusted the pool installer. They were setting the chlorinator high with thrichlor and added powders when opening and closing. They taught me to add Shock (Sodium Di-Chlor) if it got cloudy (I did this twice that year). My first test with K2006c was 6/2017 and I was at the following:
FC 16.5
PH 7.6
TA 180
CH 130
CYA 120

I spent the year getting it to where I am now. I feel like the metal magic has been raising my CH this year but not sure.

 

[JamesW]

Are you getting any scale on the pool walls?

Can you open the cartridge filter and take a picture of the cartridge before cleaning it?

Then, clean the cartridge and note anything unusual.

 

[Geckoeyes]

No scale on the pool walls. They are smooth and look great.
The next day after I noticed them I inspected and cleaned the filter cartridge but these chips did not show up on the filter at all.
This lead me to believe something going on in the heater since it is plumed after the filter.

I will check the filter again today and report back.
Thanks again.

 

[JamesW]

Was the filter blue?

It might be calcium phosphate. Maybe with copper and iron mixed in.

Maybe get the water tested for phosphate and copper levels.

 

[Geckoeyes]

No. I just checked again and the filter is pure white.

When I shut the pump off the heater shuts off too and it made some noise. When I turned the pump back on out came a couple dozen of the blue flakes out the returns.

 

[JamesW]

The heater should be allowed to cool down by turning the heater off about 5 minutes before turning off the pump.

Otherwise, the water in the heat exchanger can get too hot and cause precipitation of calcium compounds. Maybe calcium carbonate or calcium phosphate or maybe a mix of both.

The turquoise color is probably copper.

 

[JoyfulNoise]

Use of sequestering agents increases the solubility of metals in solution and therefore makes it more likely that copper metal will dissolve from the heat exchanger into solution. This is a well known phenomenon in boiler applications and it’s why boiler water is kept saturated with a positive scaling index so that a thin layer of calcium carbonate protects the heat exchanger from excess chemical wearing. You’re not in danger of dissolving your heat exchanger and JamesW is quite right as it is likely a mix of calcium scale (carbonates & phosphates) with some copper metal ions in the mix giving it a blue color.

Do you regularly use scale control products? If you don’t need to use them on a regular basis, then don’t maintain them. If you have to use them throughout the season, then you might need to adjust your chemistry a bit. Your TA is quite high and your CH is a bit low. While your saturation index might be fine with those numbers, I would consider lowering your TA to avoid scale especially because the water in your heater is very hot and higher temps will drive the scaling index to a more positive value. This will then show up as scale (with some copper mixed in) when you vacuum.

 

[Geckoeyes]

Thanks James and Matt.

Matt, No, I don't use any scale control products. Only small metal magic doses to keep stains off the fiberglass. I don't see any evidence of text book scale anywhere. Also I think your comments about my chemistry are from my 2017 values when I took over from the pool store. My first post has my current values, here they are for reference:

These test numbers have been consistent all this summer:
FC 4.0
PH 7.4
TA 75
CH 300
CYA 40
CSI -0.23

Thanks to both of you. Let me know any additional recommendations you may have. Could I just need to dial back my CH a bit with water exchanges?

 

[JamesW]

I suspect that the most important thing is to make sure that the heater isn't running when the pump turns off.