PH and TA adjustments

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T

thebassman

0
Jan 7, 2019
15
Central Florida
Pool Size
12000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Jandy Truclear / Ei
New pool build/owner
Recently had PB do some punchlist items on a new pool build. I had the water GREAT for about 2 months.
there were some equipment issues and also some work that ended up putting a LOT of dust/debris back in the pool.
I've cleaned my filter a few times this week, and just did a brief soak in diluted acid per manufacturer ... the pressure is a lot better, but still not as low as it used to be. the filter itself looks pretty darn clean though....

I am still getting some air bubbles coming through the returns - trying to find why that's happening.

Today, my water tests showed:

TC- 4.5
FC- 4.5
CC- 0
PH- 8 (has been wanting a lot of acid since day 1, kinda normal for me to expect adjusting this)
TA- 50 (usually around 80)
CH-400 (usually around 325)
CYA- 20
Salt - 2,700 ppm
TDS - 4,000 ppm

Water Temp was 75
LSI ~ 0.6
I'm starting to see a bunch of what seems to be floating dust... there's construction nearby... so maybe it's actually dust or maybe calcium?

So my question is how to adjust these values?
Pool math says 14oz acid, 85oz (weight) baking soda, 42oz liquid stabilizer

I've never had to adjust TA as yet, so i'm hesitant to do it all at the same time.

any thoughts?
 
Only target 7.8 for the pH, as the CYA will reduce it a little. TA target 70 or 80. Half an hour between additions should be plenty.

I wonder if the bubbles you're seeing aren't hydrogen gas from the SWG. With so little CYA and decent FC, that thing is probably running full time.
 
Next time just use your TF100 and post those results. We believe in them much more than the pool store test results.

Richard has you on the right track ---
 
Great - LSI is typically from a pool store --- but good you are using your test kit. Take care.
 

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Read the Pool School section of this site. pH and Alkalinity are the two concepts you should make yourself very familiar with first. Here are a few concepts that I think are helpful.

Remember your Alkalinity is mainly a buffer for the pH, it essentially keeps your pH from falling.
TA in our pools is primarily carbonate alkalinity, for the most part it prevents your pH from dropping. A high TA increases CO2 in your pool which vents off causing the pH to rise faster. An infinity edge or fountain features also speeds up the CO2 venting. With too low of a TA, the pH tends to swing about wildly, too high of a TA, and there is a constant push for a rising pH.

When chlorine (in any form) is added to water, a weak acid called Hypochlorous acid is produced. It is this acid, not the chlorine, which gives water its ability to oxidize and disinfect. One of the byproducts of using liquid bleach (sodium hypochlorite) is sodium hydroxide, which contributes to total alkalinity and raises pH. This is why you need to keep the TA at the lower end with a SWG pool. Especially when adding bleach to compensate if the SWG cannot keep up.

The ability of chlorine to disinfect is directly related to pH. As the pH raises above 8.0, its ability to disinfect is very limited. In addition, scaling (precipitation of mineral components) and cloudy water may result. pH is an equilibrium that functions like a scale measuring how acidic or how basic a substance is. pH can fluctuate up and down. And when it does, the pool is constantly fighting against you. Having the right level of total alkalinity is important, because it helps to keep the pH stabilized.

At water temperatures above 82, chlorine dissipates faster, algae grows better, and the formation of scale (Calcium carbonate deposits) is more likely to occur. So never let your chlorine drop to zero, ever.

Cyanuric Acid acts as storage unit for Chlorine. Cyanuric Acid reduces your pH a little when it's added. Since you have a Salt Water Generated System, follow the guidelines for such on this site. They are slightly different than for a regular (bleach) pool.

Calcium, Cyanuric Acid, and Salt stay in the water. The only way they leave the water is through loss of water by splashout or a leak. So you want to be thoughtful of what you add to your pool.
 
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Sharkygirl said:
Read the Pool School section of this site. pH and Alkalinity are the two concepts you should make yourself very familiar with first. Here are a few concepts that I think are helpful.

Remember your Alkalinity is mainly a buffer for the pH, it essentially keeps your pH from falling.
TA in our pools is primarily carbonate alkalinity, for the most part it prevents your pH from dropping. A high TA increases CO2 in your pool which vents off causing the pH to rise faster. An infinity edge or fountain features also speeds up the CO2 venting. With too low of a TA, the pH tends to swing about wildly, too high of a TA, and there is a constant push for a rising pH.

When chlorine (in any form) is added to water, a weak acid called Hypochlorous acid is produced. It is this acid, not the chlorine, which gives water its ability to oxidize and disinfect. One of the byproducts of using liquid bleach (sodium hypochlorite) is sodium hydroxide, which contributes to total alkalinity and raises pH. This is why you need to keep the TA at the lower end with a SWG pool. Especially when adding bleach to compensate if the SWG cannot keep up.

The ability of chlorine to disinfect is directly related to pH. As the pH raises above 8.0, its ability to disinfect is very limited. In addition, scaling (precipitation of mineral components) and cloudy water may result. pH is an equilibrium that functions like a scale measuring how acidic or how basic a substance is. pH can fluctuate up and down. And when it does, the pool is constantly fighting against you. Having the right level of total alkalinity is important, because it helps to keep the pH stabilized.

At water temperatures above 82, chlorine dissipates faster, algae grows better, and the formation of scale (Calcium carbonate deposits) is more likely to occur. So never let your chlorine drop to zero, ever.

Cyanuric Acid acts as storage unit for Chlorine. Cyanuric Acid reduces your pH a little when it's added. Since you have a Salt Water Generated System, follow the guidelines for such on this site. They are slightly different than for a regular (bleach) pool.

Calcium, Cyanuric Acid, and Salt stay in the water. The only way they leave the water is through loss of water by splashout or a leak. So you want to be thoughtful of what you add to your pool.
Click to expand...
That was an AWESOME summation. I screen shorted this for future reference whenever my buddies ask me a pool question. Perfectly put!
 
thank you - yes pool school section is very helpful. appreciate the additional info. also just ordered the K-1766 kit to check salt. will verify with accurate test and then adjust to 3000ppm.

once the PB is done with the repairs, i hope to have a better chance at keeping water more stable. i had it there for a couple glorious weeks.... was so nice to just enjoy the pool instead of chasing issues!
i still expect another round of heavy grout dust in pool....
after about 8 weeks, it might already be time for a new filter. even with following all manufacturer recommendation for cleaning, there is still higher pressure and visible air in the pump basket... and air coming out of returns. hoping new filter will fix issues and even better if it's under warranty.

I've lowered the SWG from 100% to 50%... trying to get FC to ~2ish.
Richard suggested that SWG high output might be causing some of the 'air' from hydrogen gas bubbles.

as luck would have it, earlier today the filter lid blew over onto its side while i was cleaning filter and the pressure gauge snapped off. jandy is nice enough to use proprietary threads in the filter housing, so an adapter (which also snapped) is required. both on order and hopefully arrive tomorrow. until then, everything is turned off.
test results from this morning.
73degF water
TC- 3.5
FC-3.5
CC-0
PH-7.8
TA-60
CH-425
CYA-30

so all of that is looking good, but i would still want to lower PH a bit. dont want to do that until i can run the system.

i see diff CYA levels, being told that 30-50 is good, but for SWCG i should target 70-80?
if that's right, then i'll need to add more CYA after i repair system.

CH is rising, but still seems to be in OK range. if it goes higher than 450 seems i may need to drain and fill about 25% or so of water.
does that seem about right?

thanks for all the help
 
CYA is like a built in storage depot for free chlorine. The ions of Free CL are bound by CYA until the CYA is full and what is left over is unbound Free CL. (So more CYA means more Free CL to fill it) As Free CL is lost from the pool, (by sunlight, bather load, etc.) then the ions of Free CL will be released by the CYA.

If there is no CYA in a pool then the salt water generator (SWG) will have to work harder to maintain free chlorine levels-- because there is no reservoir so to speak. This might shorten the lifespan of the SWG.

The rate at which you set your SWG will be determined by how much Free CL you lose either through sunlight evaporation or bather usage so that you can maintain normal levels. For this reason, keeping Cyanuric Acid levels higher, with a SWG, a higher free chlorine is needed to fill the CYA, but easier for the SWG to generate because the higher amount of CYA is storing more of the needed chlorine. (See the green print above) More CYA=more Free CL to be released as needed. But, when a shock is required, more Free CL needs to be added because of all the locked Free CL in the CYA. You want a lot of Cl in reserve, but the more you have in reserve, you need more to replenish the reserve.

I know you are going to need to read that above a few times. It is a concept that took me a while to really understand.

So the recommended levels for CYA with a SWG pool are as follows:
FC 3-5 (See Chart )
pH 7.2 - 7.8
TA 60-80
CH 350-450
CYA 70-80

Target CYA./ MIN CL. /Target CL. / Shock
CYA 60 / 3 / 4 / 24
CYA 70 / 3 / 5 / 28
CYA 80 / 4 / 6 / 31

With a new pool install, you are going to have to brush everyday. Your CH is going to climb a little, but I wouldn't try to correct that just now. Read more about that on this site.

I hope this was somewhat helpful.
 
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