Algae ? That won't brush off

[kne]

SLAMming my pool right now. Getting ready to install a new SWG and want to have water perfectly balanced before install. The water is very clear now, there was a lot of debris prior. There are some light brown sandy spots that don't budge when brushed. Do have hard water, was wondering if it could be buildup of some kind? If that is the case, what's the lowest PH the vinyl could take to release? I had scaling on our hot tub once and was able to lower to 7 and scrub it off after a couple of days, but not sure this is the same. This morning my PH was over 8 ( not unusual, it's something I constantly have to control throughout the season ) I lowered to 7.5 then dosed per calculator to 7.2. Since then I have chlorine too high to test. I'm going to do overnight test to set if I pass, but not sure what to do about the marks. Today I did vacuum up chunks of white calcium looking stuff from the bottom of the pool. About the size of a pinky fingernail, able to break apart.

 

[mknauss]

Post your test results. Low pH is not good for vinyl.

 

[kne]

My Chlorine levels are still too high to test PH, does chlorine affect TA & CH also? I think it's going to take a while to drift down. It's pretty overcast and cold here, there is nothing in the pool to consume the chlorine.

• FC 24
• CYA 50
• SALT 3000
• TEMP 59

 

[mknauss]

FC level does not effect the TA or CH test results.
Just wait on the FC level to drop and then test your pH.

 

[kne]

Ok, I'll see where we are Chlorine tomorrow

• TA 275
• CH ~300 I think. I'm having a hard time with the droppers in the kit.

 

[mknauss]

I doubt your TA is 275 unless you have added a lot of baking soda.

See Total Alkalinity - Trouble Free Pool

 

[Rancho Cost-a-Lotta]

Ok, I'll see where we are Chlorine tomorrow

• TA 275
• CH ~300 I think. I'm having a hard time with the droppers in the kit.

For TA test, maybe you multiplied by 25 instead of 10?

 

[kne]

I just re-ran test

• 10 ml of pool water
• 1 drop of R007
• 3 drops of R008

(Using speed stir) At 11 drops of R009 water was pretty light, at 12 turned red. So is actually 300?

I've always had hard water and use MA to control. Used to be that I only filled pool with well water which is really bad, but last year I used a lot of house water and we had lots of rain this winter with an uncovered pool so I thought the hardness would be better

 

[kne]

Ok, I swear I have tested my chlorine and know how to do it, I'm not sure what was going on in my head this morning. But I think the FC of 24 this morning was really wrong, I swear I counted 48 drops on a 10ml pour. But thinking back about how it could have got that high didn't make sense so I tested it again about 2pm and it was 8. Just retested it now and it's about 7 (3 hours later). New resolution - be methodical about logging results and adds.

• FC 7.0
• CC 1.0
• PH 7.5
• TA 300
• CH 300
• CYA 50
• SALT 3000
• TEMP 59
• CSI 0.14

If I understand correctly, the only way to get the TA down is to constantly lower PH to 7.2 and then find a way to aerate back up, lower, raise, lower, raise.

I don't know if I need to SLAM or not. The only visible issue in the pool is what looks like light algae.

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[mknauss]

Do an Overnight Chlorine Loss Test

Try posting your pictures directly in your post. Most of do not like to access pictures on other sites.

 

[marcgr]

Check that your spots aren’t really iron. If you’ve had high PH it could have deposited, and it can look like mold. Rub a vitamin C tablet on it, if it disappears like magic then it’s iron.

 

[JJ_Tex]

I just re-ran test

• 10 ml of pool water
• 1 drop of R007
• 3 drops of R008

(Using speed stir) At 11 drops of R009 water was pretty light, at 12 turned red. So is actually 300?

I've always had hard water and use MA to control. Used to be that I only filled pool with well water which is really bad, but last year I used a lot of house water and we had lots of rain this winter with an uncovered pool so I thought the hardness would be better

I don't think you are doing the TA test correctly (unless there is an alternate set of instructions for 10ml). I always use 25ml of water, and multiply the R-0009 by 10 to get my TA results.
I also pulled this from their website which matches my printed instructions on the kit:

Total Alkalinity test – TA has a buffering affect on pH, preventing it from moving suddenly. Good TA readings will be around 70-90 for salt pools and 100-120 for normal pools
1. Rinse and fill the clear plastic cylinder to the 25ml mark
2. Add two drops of R-0007 and mix. Then, add 5 drops of R-0008 and mix again. Solution will turn green.
3. Add R-0009 one drop at a time, swirling between each drop. Wipe the tip of the bottle after every drop with a damp cloth. Continue ‘til color changes to red. Multiply the number of drops you added times 10. (11 drops = T/A 110) Record it. TA can vary widely. but a range of 70-120 normally works well

 

[Rancho Cost-a-Lotta]

I don't think you are doing the TA test correctly (unless there is an alternate set of instructions for 10ml). I always use 25ml of water, and multiply the R-0009 by 10 to get my TA results.
I also pulled this from their website which matches my printed instructions on the kit:

JJ,

The test kit label does show an alternate test...

"When high TA is anticipated, this procedure may be used: Use 10 mL sample, 1 drop R-0007, 3 drops R-0008, and multiply drops in Step 4 by 25."

One possibility is old/expired reagents.

 

[kne]

Re-agents are on the newer side, don't expire until 2021 and they are always kept in cool dark place

Passed overnight test. (7.5 to 7.0)

PH was at 7.5, used 80 oz of acid to lower to 7.2. Pointed the return jet up and ran over night. This morning PH was back up to 7.5, added another 80 oz of MA. I didn't test TA this morning, will check that this afternoon. Does anyone have any idea about how long lowering TA takes?

These pictures are a couple days old now. I will take some more today.

 

[mknauss]

You can use Effects of Adding Chemicals in the app to see what the approximate TA reduction each time you add the acid to lower pH.

 

[aeh0603]

I'm sure the experts will correct me if I'm mistaken, but I believe what I am remembering is for the TA test.

Sometimes with new bottles of the TA testing reagent, static electricity can build up on the tip of the bottle and make the drop size smaller. This makes your TA seem higher than it actually is. To prevent this effect, try wiping the tip of the TA reagent bottle with a damp paper towel between each drop.

Also, for all tests, make sure you are holding the bottles vertically when dispensing drops. Do not hold them at an angle as this can impact drop size and makes your test results less accurate.

 

[kne]

You can use Effects of Adding Chemicals in the app to see what the approximate TA reduction each time you add the acid to lower pH.

Never even thought about using it for that, thanks. Checks out. Adding MA to lower my PH from 7.5 to 7.2 each time also lowers TA about 21, so this will be a few days process minimum.

 

[mknauss]

That number will change as your TA falls.

 

[kne]

Adding to note - I just tested my hot tub, which is separate and probably 100% house water (as opposed to the pool which has a very high % of well water) and the TA is right around 75. Our well is very hard, if your car gets hit by the sprinklers, getting the water spots out is a chore. I've been testing with a test kit since 2015 and these numbers have always been on the high side, but I've never addressed it before. I feel confident that the high reading is correct. I really appreciate everyone's input.

TA is down to below 275 tonight. Will repeat tomorrow.

 

[Rancho Cost-a-Lotta]

I didn't mean to question your methods. I've only been around a couple years and have not seen a TA reading that high on the forums. Sounds like you got a handle on it. Good luck!