pH dropped, couple questions

[watson524]

Hi all,

I was away for 3 weeks and my husband was managing the hot tub. Since it's been so windy here in the north east, he was only in a few times while I was gone because we sit in a big open field and any bad wind like that is brutal. He put in a 1 tbsp of Leisure time replenish after each dip (was was 3 in the last week). When we tested today we got the following numbers (note when we took the cover off, I did smell a warm water chlorine smell but not over powering - I was thinking it needed to be shocked but the numbers don't indicate that I don't think. Water is still crystal clear)

Using MPS strips for use with our nature2:
MPS - high
Ak - 100
pH - 6.2

Using the regular strips:
FC - 3.0
Ak - 80
TH - 100
pH - 6.2

Using the Taylor K-2006 kit:
pH - 6.2
FC - 6.4 (likely the MPS is interfering and causing this high reading?)
CC - 0.2
AK - 80
CH - 100
CYA - 55

So the CYA is creeping up as is known to happen with the Dichlor and I need to think about adding the borates and going to bleach or dumping about 25% of the water according to pool math.

The pH had been 7.6 to start back in late December and it looks like it's just falling as I look at the records. I assume this is because of the net acidic level of the Replenish and Spa 56.

If we let the MPS level come down, will that push the pH back up a bit on its own? I splashed the water in my eyes, nothing burned. I also ran the jets about 10 minutes to see if that aeration raised the pH but it didn't do anything.

Don't want to do anything to get into wild swings of levels but what would you do?

thanks!

 

[chem geek]

As you know from your earlier thread, Leisure Time Replenish is 72% Oxone and 15% Dichlor which means it's 31% MPS. Both Dichlor and MPS are net acidic with MPS twice as acidic as Dichlor (for the same oxidizing power).

3 tablespoons of Replenish in a 500-gallon Jacuzzi J-385 would not drop the pH very much and the TA would only drop by 2 ppm. It's roughly equivalent to adding 5 ppm FC which in 500 gallons is enough to handle around one person-hour of soaking so over 3 soaks that's 20 minutes per soak. That doesn't count what is needed to maintain a residual in between soaks. So it's surprising that the MPS level is high.

If you don't keep adding Replenish since you want the level to drop a bit, aeration with spa jets should get the pH up. It's surprising that it didn't. The Taylor kit only measures down to 7.0 or 6.8 pH depending on the kit so how are you getting 6.2?

 

[watson524]

That threw me too on the MPS on the yellow strips being so high (deep purple). Maybe I needed to aerate longer? My Taylor kit goes down to 7.0 but both strips read 6.2 and the color on the Taylor kit was definitely at least 2 "shades" lighter than the bottom. So maybe it was 6.4 - 6.6 but definitely lower than 7.0.

With the CYA creeping up to 55, is that maybe causing reading issues? Given these frigid temps, dumping water isn't a good option at this point so I may be switchin to bleach plus adding in some borates per your earlier posts.

 

[JasonLion]

The CYA level (high or low) won't affect the other test results.

Your TA is reasonable according to the tests, so some more aeration should bring the PH up.

 

[watson524]

The CYA level (high or low) won't affect the other test results.

Your TA is reasonable according to the tests, so some more aeration should bring the PH up.

Ok. Tonite we won't be in it but possibly tomorrow nite so I'll aerate the heck out of it. You'd think with a 6.2 - 6.6 range it would have bothered my eyes when I splashed the water in my eyes but it was fine.

 

[watson524]

My husband took a water sample to the store today since he was going to be in the area. Interestingly, they tested the pH at 7.0 and Hardness at 130 (which they say we should raise up a bit and I disagree and have ignored their direction in the past on that, I'm ok with where ours is at 100). But the weirdest thing, while our Ak read 80 - 100, they say it's 20 and want us to raise it up. 3 of my test methods show the 80 - 100 so I'm not sure why theirs is so off from ours but I'm inclined to ignore suggestions to bring that up unless anyone has a different opinion or a reason on why our test 3 times show things more consistent and higher. 20 seems like a huge drop from what even the store has tested it at in the past (80 - 100 range). Seems like a test error.

If they have the pH at 7.0, I definitely think aerating tonite is the way to go.

 

[chem geek]

The dropper tip for the R-0009 TA drops can get static electricity in which case the drops squirt out too small so you get an artificially high reading. Wipe the dropper tip with a moist cloth to prevent this. You want well formed drops that hang before leaving the dropper tip.

Note that both Dichlor and MPS will lower the TA over time but as I noted it's slow since 3 tablespoons of Replenish would lower the TA by around 2 ppm.

 

[watson524]

But I got 80 - 100 on 3 different tests, two different strips and the Taylor kit. I'm wondering if they had some kind of issue on their testing perhaps?

 

[chem geek]

If your tests were consistent, and most importantly if the drops were good in the Taylor test, then your results are very likely correct. Sounds like they did have a problem with their testing.

Note that your quite low pH readings usually would not occur with the TA you have if you have aeration in the spa.

 

[watson524]

Ok I'll test again tonite with the drop test just to be sure. We were in it last nite for about 40 minutes and the MPS level was reading low so that's at least come down. Not sure why it was so high given what my husband put in it but that's sorted now. The Ak on the MPS strip still reads as 80 and the pH read 7.0 so I'll check that again with the drop test to see what's what.

 

[JamesW]

Have you used a ph "lock" product? Such products use phosphates to provide a non carbonate buffer. A TA of 80 in a hot tub with hot water and aeration would usually result in rising pH. Your low pH is unusual for that TA.