I must have missed HCL acid in the chemistry 101 class

rock

Well-known member
Apr 26, 2012
263
#1
I 'thought' I understood the chemistry 101 here but I'm having to put HCL in my pool about once a week lately to keep it at a pH of about 7.5.

What is weird is that the Leslie's pool reports come back 'clean' except for the need for acid.

What I don't get is if the buffering is fine, why do I need to add acid weekly?

Note: I don't have my results on me so I'll run a test this week at Leslies and report the complete chemistry.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
41,197
Tucson, AZ
#2
Do you have a water feature, spa spillover, or SWG? All of then aerate the pool and thus raise the pH. Also if your TA is high, this too pools the pH up.

Not uncommon for people to have to add acid every few days.

Posted with Tapatalk ... sorry if I sound short ... hate typing on phone ;)
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
#4
Don't try to keep the PH at 7.5, that is too low. Keep the PH around 7.7, it won't move nearly as much from there. Your TA is probably too high as well. High TA means the PH will be driven up more quickly. If you post a complete set of water test results, we can give you more specific advice.
 

Isaac-1

TFP Expert
LifeTime Supporter
May 10, 2010
6,711
SW Louisiana
#6
There really is no one answer to this question, sure TA may be an issue, but so may be the acidity of blown in dust in your region, ...

Ike

p.s. you really should invest in a good test kit, I use the TF-100
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,330
San Dimas, CA (LA County)
#7
I'll tell you why: you have hard water, which includes high TA. I was born in San Jose and lived there for 40+ years, and the water is hard. You have white crust on your shower heads, most likely. Your coffeemaker slows down as it clogs with deposits until you stink up the house running vinegar through. Am I right?
 
OP
OP
R

rock

Well-known member
Apr 26, 2012
263
#8
jblizzle said:
Do you have a water feature, spa spillover, or SWG? All of then aerate the pool and thus raise the pH.
The pool is typical chlorine (for which I use liquid chlorine + three 3-inch tab floating feeders.
Speaking of aeration, I had not realized that 'might' be an issue.

It turns out there is a massive leak in the solar panels (long story, separate), so I 'am' adding 500 to 1,000 gallons every couple of days.

It's not a water feature, per se ... it's just adding water through a hose via an Ace Hardware water meter switch that we manually set to 500 gallons for every inch that we need the water level to rise.

Do you think 'that' is raising the pH?
 
OP
OP
R

rock

Well-known member
Apr 26, 2012
263
#9
Richard320 said:
you have hard water, which includes high TA. ... You have white crust
Everything you said is right on the money. :)

The water is so hard that even a cold-water garden hose has beautiful white crystals on the inside. The coffee pot is cleaned weekly with vinegar because of the white slime that forms almost immediately. All the shower heads and faucet heads likewise have to be cleaned in vinegar, every few months, because they clog up like the Garden State Expressway on memorial day.

However, when tested, the well water is about 220 ppm calcium, which is very hard for drinking and cooking - but I'm told it's PERFECT for built-in pools. So I don't have to add 'any' calcium for the pool to have the right CH. I'll double check the TA though, and report back.

Maybe it's the TA after all ... even though it's within reason.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
41,197
Tucson, AZ
#10
adding water due to your leak is not aerating your pool.

You said you used liquid, but now state your float pucks too ... watch your CYA if you keep that up.

Posted with Tapatalk ... sorry if I sound short ... hate typing on phone ;)
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
#11
The rise in pH mostly comes from carbon dioxide outgassing and that can be minimized by lowering the TA level. If you lower it a lot and want more pH buffering, you can use 50 ppm Borates. If your fill water is high in TA, then evaporation and refill will increase the TA over time (same with CH). Basically, evaporation and refill adds whatever is in the fill water to your pool. pH can also rise from fresh plaster. It also rises from the excess lye in chlorinating liquid and bleach, though the amount varies depending on the quality of such product (some have lower excess lye -- Clorox Regular has some of the lowest; off-brand bleaches tend to be higher).

Remember that pools are intentionally over-carbonated to provide pH buffering (ironically) and to saturate the water with calcium carbonate to protect plaster surfaces. However, TA is a SOURCE of rising pH due to carbon dioxide outgassing. This post shows the equilibrium pH at various adjusted TA (carbonate alkalinity) levels so shows the pH at which carbon dioxide outgassing will stop. In practice, it slows down significantly before then so I also show the pH at which there is twice as much carbon dioxide in the water as compared to equilibrium with air. As you can see, even our lowering the TA to 70 or 80 ppm still has the pH rise and even at 50 ppm it still would rise, but the rate is much slower. Usually, though, 50 ppm is only a TA level needed in spas where there is a huge amount of aeration when jets are used.
 
OP
OP
R

rock

Well-known member
Apr 26, 2012
263
#12
jblizzle said:
adding water due to your leak is not aerating your pool.
Oh. OK. It bubbles about 1 foot into the pool from the edge of the hose.

jblizzle said:
You said you used liquid, but now state your float pucks too ... watch your CYA if you keep that up.
Yes. I use both. I just bought three 8 pound containers of cyanuric acid as I refill the pool every year so it was zero.
I put in 16 pounds of CYA into the pool and Leslie's tested the result a week later at 50ppm (which I was surprised at since the Leslie's calculation called for something like 22 pounds).

Anyway, the liquid HASA chlorine is what I have been using since I refilled the pool a few months ago. I use three floaters too, but they really don't do much at all. If I didn't add the liquid chlorine, the levels would be too low.

I get the CYA tested every month. With my solar panel leaks, I'm adding so much water weekly that I'm not too worried about CYA levels at this point.
 
OP
OP
R

rock

Well-known member
Apr 26, 2012
263
#13
Isaac-1 said:
so may be the acidity of blown in dust in your region,
It's not to my knowledge a 'dusty' environment. The pool collects leaves - and pillbugs - and once in a while a tree falls into the pool - but dust doesn't seem to be a problem where I am.