7.2 vs >8.2 Grrrrrrrrrrr

[Infidel]

Since switching to the BBB method I'm using a Taylor test kit. I'm constantly fighting algae, keeping my Cl high ~20ppm (80ppm CYA).

The Cl doesn't appear to be working, even at shock levels >25ppm.

My Taylor kit says the pH is 7.2, my poolmaster kit says my pH is >8.2.

WTF???? is going on. I realize I've got a lot of chlorine to neutralize with the sodiumthio, so I'm adding 2-3 drops of reagent 4 (poolmaster kit) prior to the phenolphthalein. Doesn't matter, still reading >8.2.

I'm starting to believe the cheap poolmaster test because the cl is appearing innefective. Could the premixed Taylor reagent not have enough sodiumthio in it for high Cl levels, giving a bad pH reading?

I'm about to start dropping the pH level, in spite of what the Taylor kit says. It's a new kit btw, only got it two weeks ago, reagents should be fresh.

[mjs31]

Since switching to the BBB method I'm using a Taylor test kit. I'm constantly fighting algae, keeping my Cl high ~20ppm (80ppm CYA).

The Cl doesn't appear to be working, even at shock levels >25ppm.

My Taylor kit says the pH is 7.2, my poolmaster kit says my pH is >8.2.

WTF???? is going on. I realize I've got a lot of chlorine to neutralize with the sodiumthio, so I'm adding 2-3 drops of reagent 4 (poolmaster kit) prior to the phenolphthalein. Doesn't matter, still reading >8.2.

I'm starting to believe the cheap poolmaster test because the cl is appearing innefective. Could the premixed Taylor reagent not have enough sodiumthio in it for high Cl levels, giving a bad pH reading?

I'm about to start dropping the pH level, in spite of what the Taylor kit says. It's a new kit btw, only got it two weeks ago, reagents should be fresh.

I thought a low PH caused Algea. May be incorrect, but if this is true and your Taylor test kit is accurate, you would be hurting yourself. Again...I may very well be wrong on the ph/algea thing. You should wait for the experts to give you an answer.

[Infidel]

I added some acid to the pool and the poolmaster kit was responsive right away, pH now reading in the 7.6 range.

I took the Taylor kit and added some additional sodiumthio from the poolmaster kit before the Taylor reagent (004), and the kit was reponsive at 7.6.

[del]FYI, in my opinion, the Taylor reagent 004 does not contain enough sodium thiosulfate to adequately neutralize the Cl in high Cl pools. Supplement with some sodiumthio of your own for an accurate reading.[/del]

[Infidel]

I thought a low PH caused Algea. May be incorrect, but if this is true and your Taylor test kit is accurate, you would be hurting yourself. Again...I may very well be wrong on the ph/algea thing. You should wait for the experts to give you an answer.

Lack of Cl will allow algae to grow, high pH will lock up the Cl making it innefective, which is why I have 25ppm Cl with no affect. The Taylor kit doesn't appear to be accurate but I'm not sure what damage low pH would cause with regard to algae.

[mjs31]

Lack of Cl will allow algae to grow, high pH will lock up the Cl making it innefective, which is why I have 25ppm Cl with no affect. The Taylor kit doesn't appear to be accurate but I'm not sure what damage low pH would cause with regard to algae.

I can see your point on locking up CH levels, But low levels of PH will dissapate your chlorine requiring you to use more. Essentially this could lead to algea issues as well. Not sure which is accurate and which is not. I have the Taylor kit and it has helped me out greatly over the past few days. I do stress to wait for an accurate response from the experts in this forum. They can do wonders.

[duraleigh]

Anybody can write anything they want and post it on the net. Nevertheless, This excerpt was taken from an article about chlorine that seemed quite believable and well thought out. It should answer your questions about the relationship of Cl and pH

The amount of hypochlorous acid and hypochlorite ion that is produced when chlorine is added to the water is directly related to the pH of the water. At a pH of 6.0, 96% of the chlorine will become the desired "killing" form of chlorine, hypochlorous acid. At a pH of 7.0, 75% of the chlorine will become hypochlorous acid and at 8.0 the hypochlorous acid concentration is only 25%. At a pH of 7.5 (the average spa) the amount of hypochlorous acid produced is about 50%.

[waterbear]

I added some acid to the pool and the poolmaster kit was responsive right away, pH now reading in the 7.6 range.

I took the Taylor kit and added some additional sodiumthio from the poolmaster kit before the Taylor reagent (004), and the kit was reponsive at 7.6.

FYI, in my opinion, the Taylor reagent 004 does not contain enough sodium thiosulfate to adequately neutralize the Cl in high Cl pools. Supplement with some sodiumthio of your own for an accurate reading.

Actually, the taylor pH reagent (phenol red, not phenolphthlalein!) is corrected up to about 15 ppm. If the chlorine levels are too high for the phenol red reagent with any kit you will get high pH readings, not low! (reasons are technical so I will not post them here. I have posted them in many other threads but in a nutshell the phenol red is converted to chlorophenol red which tests the pH range of 4.6 to 6.8.) Adding the sodium thiosulfate chlorine neutralizer works up to a point but it does raise the pH of the test sample which explains why the taylor reagnet read a higher pH when you added it. I would believe the taylor reagent! The poolmaster reagent obviously is not corrected for high chlorine levels, hence the reading of 8.2. Your actual pH is way below that. because of the interference all that purple color you are getting means is that the pH is above 6.8!
My advice is to either test you pH with a properly calibrated pH meter or allow your chlorine levels to drop to about 6-8 ppm, which is as high as you need to run it for a CYA of 80 ppm! High chlorine can also interfere with the TA test and might interfere with the CH test so you might want to check all of these when the pH is lower. I would also suggest redoing the CYA test and see if you get the same results. I suspect that your CYA is either higher than you think or you have not kept your chlorine levels up high enough and have let them yo-yo up and down which will not kill the algae. How are you testing for chlorine? Are you using the DPD test in the Taylor K-2005 or the FAS-DPD titration test in the K-2006? If I am not mistaken the Poolmaster test kits have OTO which only tests total chlorine.

[waterbear]

Anybody can write anything they want and post it on the net. Nevertheless, This excerpt was taken from an article about chlorine that seemed quite believable and well thought out. It should answer your questions about the relationship of Cl and pH

Pretty much true. The ratio of any weak acid to it's corresponding ion (in this case hypochorous acid/hypochorite ions) is pretty much pH dependant!

[Poolsean]

"Lack of Cl will allow algae to grow, high pH will lock up the Cl making it innefective, which is why I have 25ppm Cl with no affect. The Taylor kit doesn't appear to be accurate but I'm not sure what damage low pH would cause with regard to algae."

With the high chlorine and no affect on the algae, you're probably dealing with high phosphates as well, which is just allowing the algae to feast in your pool. Check and treat for phosphates.

[waterbear]

Good point Sean, This might be one of the cases where phosphate removers are actually called for. Test your phosphate leves and also test your nitrate levels. If phosphates are high and nitrates are low then phosphate remover might work for you!