Light brown stains from pool need suggestions

[phillipjko]

Ok, let's go through this slowly.

First off, stop listening to your neighbor. Rain water has no metals in it (where would the metals come from??). Rain water is actually a good thing in your case because it is pure water and if you let it fill your pool (while removing old water) then you can naturally reduce your metal levels. But for now, forget about metals as your water quality is more important at the moment.

@FBU is correct, your pH is waaaaaaay too low. Borax is one way to raise it but you have very low TA so, if you can find it, you can use washing soda (sodium carbonate....NOT BAKING SODA which is sodium bicarbonate). Pure sodium carbonate is not easy to find in the stores, but sometimes you get lucky. Pool stores sell it but at a major price markup. Borax (20 Mule Team) will raise pH without raising alkalinity but you shouldn't have more than 50ppm of borates in your water and I don't want you to create one problem trying fix another.

@FBU is also right in that I don't understand your chlorine numbers. I need to know free chlorine (FC) and combined chloramines (CC). Please retest those and report. If your CC's are high then your water is definitely NOT OK. You can have clear water and high CCs which is typically indicative of a nascent algae bloom.

I see you have an SWG. How old is it? The Cu you have in your water could be coming from old or damaged plates in the SWG. With your pH so low, you could have easily damaged the coating on the SWG plates and exposed the Cu metal underneath. But for right now, you are not going to run the SWG. You should do all of your chlorination manually using liquid chlorine (bleach) until we get your pool water under control.

How confident are you with that CYA test? CYA of 0 is unusual but not unheard of in winterized pools. Certain types of Bacteria and algae can consume CYA during the winter and produce ammonia. Sometimes a 0 reading is caused by operator error during the test OR because your other water values are so far off that the CYA test is not accurate (especially with your pH being so acidic).

Which leads me to another question - how did you get those pH values? The K-2006 kit uses phenol red indicator which doesn't show color changes below 6.8 and certain can't read down to 5.4.

Please respond with the following water parameters using the K-2006 :

FC
CC
TA
pH
CYA
CH (this one is not very important to get right at the moment).

DO NOT ADD ANY CYA UNTIL YOU GET A FULL SET OF RESULTS. If your CYA test is off and you do have CYA in the water, you do not want to overshoot as the only way to lower CYA is by draining.

Currently the following values are


FC 50
CC 0
TA 120
pH 7.2
CYA 20
CH 300
copper 0.2

Water is now clear.. but the stains are kinda coming back strangely. Under direct sunlight they look fine

https://www.flickr.com/photos/128250...posted-public/
https://www.flickr.com/photos/128250...posted-public/

but under shade there are browning maybe one would call copper stains.

[SunnyOptimism]

Currently the following values are


FC 50
CC 0
TA 120
pH 7.2
CYA 20
CH 300
copper 0.2

Water is now clear.. but the stains are kinda coming back strangely. Under direct sunlight they look fine

https://www.flickr.com/photos/128250...posted-public/
https://www.flickr.com/photos/128250...posted-public/

but under shade there are browning maybe one would call copper stains.

I'm still confused by that FC number. Is it 50ppm or drops? If drops, then what samples size did you used, 10mL or 25mL?

There's a way you can determine what the stain is. You'll need a 3" trichlor tablet and a high concentration Vitamin C tablet. You put the trichlor tablet on the stain and if the stain lightens or disappears, then it is likely algae. If the trichlor tablet doesn't get rid of the stain, then try the Vitamin C tablet. If it lightens or disappears with application of the Vitamin C tablet then it is likely a metal (Cu or Fe). DO NOT LEAVE THE TABLET ON FOR A LONG PERIOD OF TIME AS THEY CAN ETCH A PLASTER SURFACE AND FADE VINYL.

If the stains are metals, then we'll have to run through an ascorbic acid treatment process.