SHOCK is raising pH

PoolFloater

New member
Aug 17, 2010
3
Hi all, I am new to this forum. I have had my pool since the beginning of summer. It is a 18'x48". I have a salt water pump that pumps 2000g/hr.

My pool is doing great, I am absolutely LOVING the saltwater chlorination system. What I love the most is that all I really have to maintain is the pH and I'm good. I haven't added anything but acid, shock and baking soda. I try and keep the pH around 7.2-7.4--I like for the pH to be a bit on the lower end... My question is that if one shocks the pool how does the shock work properly when it raises the pH sky high? I have read that chlorine doesn't work as well if the pH is high. So how does the shock work then? Is it b/c the level is SOO high?
 

dmanb2b

TFP Expert
LifeTime Supporter
Apr 4, 2009
3,734
NY
Welcome to TFP...you should read pool school. There is no reason to add shock to your pool if you test your FC level consistently. Depending on your CYA level, your FC may be too high. A saltwater pool is a chlorine pool. FC levels above 10ppm cause PH tests to read falsely high.

Post a full set of results and we'll be able to help you out :goodjob:

FC
CC
TC
PH
TA
CH
CYA
 

PoolFloater

New member
Aug 17, 2010
3
Thanks DMan, lol... I have a standard liquid test. I know the salt water is a chlorine pool, lol :) I personally don't have to add shock (well, there was that one time, hahaha, I had grn funk growing on the bottom and I super shocked it, 4 bags of shock! and that took care of the funk), my friend does. We have the same setup and I was mainly asking for her. She has SO many problems with maintaining her water. I don't have any! I check my water daily. And adjust pH if needed, which is only after we have heavy rain. I've been trying to help her with the water, i.e. checking her water and adjusting pH to the right range. She thinks it's not holding chlorine long enough. I tried to explain that it won't hold high level for the full 24hrs(she is running chlorinater for 9hrs), when I test mine about 20hrs later with the liquid, mine reads real light yellow ( not sure what level that is).

Anywho, she raised the question today that if she shocks it this will raise the pH and the chlorine won't work like it should. From what I have read this is true. Should I suggest to her to use the shock that does not have chlorine in it? Also, does the shock still work if the pH is out of range?

Thanks
 

frustratedpoolmom

TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
12,223
SWSuburban Chicago, IL
The PH rise is temporary, and as the chlorine is used up the ph will drop back to normal. Disregard high PH readings. We recommend shocking with liquid chlorine - granular products add additional things that you may not want in your pool. Non-chlorine shock is really meant for use in spas, or indoor pools.

Why are you adding baking soda?
 

PoolFloater

New member
Aug 17, 2010
3
I add baking soda to raise pH if I need to, though that is very very rare. That's the cheapest way for me. I kinda thought the pH being high was temp. But I still don't understand how the shock works with a high pH :?: :?: . I mean shock is designed as a super chlorinatior so it has to work, I guess I just want to know to much! LOL :-D

I find it quite bizarr that she is having so many problems, we live just a few miles apart. She is wanting to add all this crazy stuff and all I have added is salt, acid, baking soda and shocked it once. This is why I choose saltwater, I didn't want to add all those crazy chemicals to my water.
 

bk406

Well-known member
Dec 3, 2009
2,690
Central Massachusetts
You want to use borax to raise the pH, not baking soda. While it will increase the pH some, it also raises the TA. The TA should be set and allowed to remain stable. 20 Mule Team Borax should be used to increase the pH when you want to keep the TA where it is.
"shock" is not a product, its a process. Adding chlorine to your pool to increase the FC level and fucntion to kill algea/bacteria/virus' is independant of the pH, basically.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
PoolFloater said:
But I still don't understand how the shock works with a high pH :?: :?: . I mean shock is designed as a super chlorinatior so it has to work, I guess I just want to know to much! LOL :-D
When there is Cyanuric Acid (CYA) aka stabilizer or conditioner in the water, then the chlorine effectiveness does not drop as much at higher pH (this is shown technically in this post). The industry rule about higher pH lowering chlorine effectiveness applies more to when there is no CYA in the water.
 

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
23,391
SouthWest Alabama
If your friend shocks every week using Dichlor then her CYA level might be astronomical. You really need to check it to know that her FC for her CYA level is correct.

Also the complete set of test results that Dman asked for would help us greatly.
 

Darkside of the Pool

LifeTime Supporter
Jul 20, 2010
106
Also...
Saltwater Chlorine Generators makes pH rise.
This effect can be kept in check along with a lower alcalinity, but found strange no one mentionned it.

Also, as mentionned, proper chlorinating, even with a SWCG, should include CYA. This will expand your cell's life somewhat by reducing its use, greatly lowering the effects of an higher pH too. Less run-time also means less PH-rise.

I wouldn't advise shocking unless there's something going on in the pool. Testing PH while the pool's shocked will give you a false reading. Read the label on your shock product.

Most parameters are best left in balance, that is why you have to be careful what you shock with.

Calcium Hypochlorite: Regular use will raise your calcium over time. Can both be beneficial and detrimental. (High pH. Somewhat reduced effect when it is used up.)

(...)dichloro-s-triazinetrione, or (...)isocyanuric: Regular use will raise your CYA. Can both be beneficial and detrimental. (Rather stable pH. Somewhat acidic when chlorine is used up)

Sodium Hypochlorite: Bleach. Regular use will raise your Salt Level. Usually help to compensate salt loss to backwashes and splashes. (High pH. Somewhat reduced effect when it is used up.)

Lithium hypochlorite: I'll resume by saying: if you have THAT much money, make a donation (like I'm supposed to.)

(...)trichloro-s-triazinetrione: Just kidding. Too slow acting to be sold as a shock product. VERY ACIDIC. Will raise CYA.