Is it normal for PH to go up right after adding LC

[Decoy205]

Been pretty consistent with my results lately. My numbers everyday this past week have been as follows:

FC 4.5-5
CC 0
PH 7.5
TA 70
CH 60
CYA 40

I have been adding approximately 33oz of LC each day per pool math to get the FC up to around 7 either around 1ish or 7pm.

Today tested at 7pm and got 4.5 for FC and all the same numbers as above.

I added a little extra chlorine this time to get it to 8ppm because I won’t be home until the evening tomorrow and it’s going to be 96 and super hot.

I wanted to confirm my FC after so I tested FC and PH I only waited about 10 mins or so.

FC bumped up to 8ppm as expected but Ph bumped up to 8ppm

Is it normal for PH to go up like that right after adding LC? I think I read that here but wanted to confirm.

 

[Newdude]

it normal for PH to go up like that right after adding LC? I think I read that here but wanted to confirm

It's a pool store myth that's HUGE and gets regurgitated all over. The PH of LC is 13-ish so it will raise your PH with continual use, goes the scare tactic. (So use pucks)

Except it's a drop in the proverbial bucket when mixed with your 10k gallons of PH 7 water. A 7.5 PH will go up to 7.5013 for you.

Point 0013.

Yeah. No.

 

[Decoy205]

It's a pool store myth that's HUGE and gets regurgitated all over. The PH of LC is 13-ish so it will raise your PH with continual use, goes the scare tactic. (So use pucks)

Except it's a drop in the proverbial bucket when mixed with your 10k gallons of PH 7 water. A 7.5 PH will go up to 7.5013 for you.

Point 0013.

Yeah. No.

That’s weird then! Why would my PH go from 7.6 to 8ppm or higher so quickly? The only change was adding the LC?

I’ll check my numbers in the am again. I have dry acid to reduce if needed. So far I haven’t had to lower ph at all but it’s only been a month.

 

[NeuronBasher]

That’s weird then! Why would my PH go from 7.6 to 8ppm or higher so quickly? The only change was adding the LC?

I’ll check my numbers in the am again. I have dry acid to reduce if needed. So far I haven’t had to lower ph at all but it’s only been a month.

Did you happen to test it in the same spot you poured the liquid chlorine before it had been thoroughly mixed with the rest of your pool water?

 

[Newdude]

Was it breezy ? I had a real hard time over the weekend getting the drops to fall in the block without overdoing it in the wind.

 

[Decoy205]

Did you happen to test it in the same spot you poured the liquid chlorine before it had been thoroughly mixed with the rest of your pool water?

I added the chlorine at the return as I always do. The return has a good amount of pressure so
It should circulate quickly.

I waited a min of 10 mins it was probably more like 12 and retested from The opposite end of the pool.

 

[Decoy205]

Was it breezy ? I had a real hard time over the weekend getting the drops to fall in the block without overdoing it in the wind.

Nope. I tested twice cuz I was very shocked at the quick jump.

 

[NeuronBasher]

Wouldn't hurt to run out and test again if possible just to confirm the pH change since it doesn't make sense. When I get numbers that don't make sense I always assume I messed up the testing procedure and test again to validate them.

 

[Decoy205]

Sorry must have posted at the same time. I tested it twice ha. When I got that result I got another sample to confirm.

A little before 7pm

FC 4.5
PH 7.5/6

Added about 38oz of LC waited 10-12 mins
Tested again
FC 8
PH 8

Thought it was weird got more water tested ph again. 8 again.

Gonna wait until
The am and see if that makes a difference.

 

[mgtfp]

The chlorination cycle with bleach is pH-neutral. Important is the word "cycle". Adding bleach raises pH. Once the added FC has been used, pH is more or less where it was before.

When maintaining target FC, the resulting pH-fluctuations are fairly small, but when adding larger amounts of bleach and maintaining the higher FC (e.g. during a SLAM), the effect can be significant. That's why it's important to lower pH before a SLAM.

Here a post from chem geek with a few examples:

Use MA to neutralize pH effects of bleach?

When you guys add bleach, do you also add some muriatic acid to neutralize the pH effects? From other sites i've read, 1 gal of sodium hypo is pH neutralized with 5 fl.oz. of MA. If i'm gonna shock and initially bring the pH down to about 7.2 for higher sanitation strength, adding several...

www.troublefreepool.com

The rise from pH 7.5 to 8.0 you are reporting when increasing FC by 4 sounds a bit much.

I calculated that through with your water parameters with chem geek's spreadsheet:

FC: 4 -> 8 -> 4
pH: 7.5 -> 7.74 -> 7.507

The difference of 0.07 between start and end are the "0013" that Newdude was referring to. But inbetween, pH was higher.

To get up to pH 8, your TA needed to be much lower, like 30ppm.

 

[Decoy205]

Thanks! I’ll retest today. This is why color match tests are tricky. Maybe the darker evening light was skewing my read. I usually go into the shade for ph tests and hold the block up to the sky to get a light even background.

 

[Decoy205]

So retested this am. FC at 8 and PH at 7.7. I’ll test again tonight when I get home from work. My guess is I’ll be close to my normal readings.

Btw the order of my testing usually goes
FC > CC > PH > TA > CH. Wonder how much order influences the results.