High Alkalinity, can't keep stable

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
bnairb
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High Alkalinity, can't keep stable

Postby bnairb » Thu 01 Jul, 2010 08:30

Morning all.

Sorry this might seem so long, but I've been battling alkalinity for 3 months and it's driving me insane. My local pool stores aren't much help with knowledge. What factors would cause the alkalinity to keep going back up?

I started with muriatic acid, then ph up, but it was a roller coaster. Switched to the ph down then aeration method to bring the ph back up. The method does work but after a day or 2, my alkalinity goes right back up.

Here's my current stats. Not precise as I'm just using the aquacheck strips.
Total Hardness: About 250
Total Chlorine: around 3
Free Chlorine: around 3
pH: bet 7-7.5
Total Alkalinity: Around 150-180+ (this ones hard to read on the strip)
Cyanuric Acid: I believe somwhere bet 30-80, difficult to read

To begin, past years have always required Alkalinty Up. Pretty sure I had to put some in when I opened this year. Pool store says a few other people have said Alkalinity higher than past years.

At the begining of the season I also add Calcium Chloride to get the hardness up. Incoming water is well water, through sediment filter to remove suspended iron, then through water softener, so when opening I add the Calcium Chloride to get the hardness up.

I'm using zeolite instead of sand.

Once a week I put in Pool Perfect + Phos free to keep the phosphates down, which means I don't need to use algaecide.

Every couple of weeks I shock it.

I have an inline chlorinator using Ez Chlor Big tabs trichlor

Like I said incoming well water is filtered and softened. Softener uses salt pellets with iron/rust remover, just in case that's a factor. The pool has an autofiller, so I don't know when it might have topped off at any given point.

I also use a plastic bubble solar cover.

So I add pH down and get the Alk down to about 80, then aerate and bring the pH back up to about 7-7.5.

4 days ago over the weekend, Alk was fine. We swam Sunday, I left the bubble cover on all day Monday, and when I got home Monday the Alk was back up to around 150-180+. So I thought is was either the Pool Perfect I put in Friday, or sunblock lotions from swimming, or leaving the bubble cover on all day Monday, or I'm sure the pool filler filled withing this time frame :silent: .

I added more pH down, aerated Tuesday, Tuesday night all looked fine, Wednesday left the bubble cover off during the day to rule that out, did not swim, left aerator running and Wednesday night Alk back up again.

One other note: I do live in the woods so I'm subject to some leaves, twigs and pine needles getting in the pool.

So what could causing the Alkalinity to not remain stable? Is it something I'm using like the calcium chloride (again only add once per year), the Trichlor tablets, possibly the salt pellets w/iron remover in the softener, the pool perfect enzymes. I don't know where to start. I'd rather not battle using pH down and aerating all season. Something just doesn't seem right.

I was worried about the pool heater (heat pump) but I just looked at the manual and it says:
PH LEVEL 7.4 to 7.8
CHLORINE CONCENTRATION 1 to 5 PPM
TOTAL ALKALINITY 100 to 200 PPM
CALCIUM HARDNESS 100 to 300 PPM

So I guess the Alkalinity is close to, but not yet out of range. Am I worrying over nothing? The pool looks great, crystal clear.

Thanks for your time.


chem geek
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High Alkalinity, can't keep stable

Postby chem geek » Thu 01 Jul, 2010 20:36

The TA should only rise by adding either pH Up (sodium carbonate) or Alkalinity Up (sodium bicarbonate) or from evaporation and refill with water though usually it has to be somewhat high in TA to see a more rapid increase. It could also be some sort of testing error, especially if you are using test strips.

You lower TA by following the procedure in this post. You most definitely do NOT use pH Up in the process.

Trichlor is acidic so should lower pH and also TA over time. So I don't see anything other than the pH Up that you added that would cause the TA to rise. Maybe your specific brand of Trichlor has some sodium carbonate in it (I doubt it, but you never know -- some have been known to have borates while others have some copper).
bnairb
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High Alkalinity, can't keep stable

Postby bnairb » Fri 02 Jul, 2010 09:49

Thanks chem geek. I did switch in May to using ph down to get the Alk down and then aerating to get the ph back up. I had been using muriatic acid, then ph up in April/May but it didn't work very well. pH down/aeration is pretty easy.

My incoming water tests on the strip very soft (it's softened like I said), pH is around 6-6.5, Alk looks about 80-100. I thought it might be incoming water alk about a month ago so I tested it then too, was about 80-100. So the alkalinity of the incoming water shouldn't be changing the overall pool. For troubleshooting, 2 days ago I put in a couple pounds of pH down. I shut off the incoming water supply. Next morning (yesterday) tested about 80 or 90. I left the bubble cover off yesterday during the day and tested again last night. Alk seemed about the same. This morning I still left the water supply off but left the bubble cover on all day. I'll test again when I get home.

I was thinking maybe something changed with the trichlor since I started with a new bucket this year, but I can't imagine they'd change their formula from last year.
chem geek
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High Alkalinity, can't keep stable

Postby chem geek » Fri 02 Jul, 2010 12:27

bnairb wrote:I thought it might be incoming water alk about a month ago so I tested it then too, was about 80-100. So the alkalinity of the incoming water shouldn't be changing the overall pool.

This is not true unless you are replacing pool water with fill water through dilution such as from backwashing, splash-out, carry-out, etc.

It is more likely that your water is getting replaced via evaporation and refill and this will ADD whatever is in the fill water into your pool. This is because evaporation only removes water and nothing else while refill adds whatever is in the fill water (usually TA and CH) to your pool.

Depending on where you live, evaporation could be 1/4" per day or more so over one month that is 7.5" which for a 4.5' (54") average pool depth would be 14%. So the TA could increase by around 13 ppm per month. If there is more evaporation, then the rate of increase could be higher. The counter to this is rain overflow since that usually dilutes the water. So living in a hot desert-like environment with dry air, minimal summer rain, and fast evaporation results in noticeable increases in TA and CH over time.

This would not explain a large increase in TA over 4 days that you said you saw which is why I believe that is testing error. Test strips are not generally accurate. You really need to get yourself either the Taylor K-2006 or the TF-100 .
bnairb
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High Alkalinity, can't keep stable

Postby bnairb » Tue 06 Jul, 2010 14:30

Here's the latest. Alk was at about 80-100 Sat,Sunday and Monday. This morning (Tuesday) was back up to what looks like around 180 on the strips. There were only a couple of variables I can think of at this point. I still have the autofiller off, so no new water was added over the weekend. I did not add any Pool perfect, shock. or anything like that. We did swim a few times Sunday & monday as temps were in the upper 90's and we were off for the Holiday weekend, so I was thinking it must me the suncreens or something related to us getting in the pool (just two of us). Then I remembered that on Sunday, the chorine level was low so I added 6-8 big tabs to the chlorinator.

So could the sunscreens/people or the trichlor tabs really be contributing to this? Also, if Alk is about 180, how much pH Down should it take to bring the Alk down to 80? (18x36, which I think is about 22,000-24,000 gallons). Seems like last time I put in about 2lbs pH Down to get back down to 80, but I didn't measure it. I'll add some again tonight and see how much gets me where on Alk level. If those calculations aren't logical, I'm wondering if one of the factors (sunscreens/Trichlor tabs is giving a false reading on the strips, and like you said, maybe I should get a different method of testing. I think I'll order one of the other test kits.
chem geek
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High Alkalinity, can't keep stable

Postby chem geek » Tue 06 Jul, 2010 16:24

You've got some sort of test error. Adding chlorine can make the pH and TA move together, but the TA won't move as much as you've seen. Yes, perhaps something else in the water is interfering with the TA test in your test strips which are known to be unreliable. Please get yourself the Taylor K-2006 kit or the TFTestkits TF-100 kit I linked to earlier. You won't regret it.
bnairb
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High Alkalinity, can't keep stable

Postby bnairb » Thu 15 Jul, 2010 11:27

Got the Tftestkit. Guess what? Alkalinity 80. Thanks for the suggestion. So then I wanted to give my pool store the info but thought I'd confirm the test strips. First 2 showed 150-180 range, next 3 showed 80. I first thought I had bad strips, but I was using 2 different bottles, plus the pool store guy used his (same brand/type) and showed 180. I think I did have high alk at one point, but obviously the strips are unreliable as 5 in a row within a few minutes shouldn't show different results, or perhaps i have high alk hands and didn't hold it right :) who knows.

So I think I'll use the strips during the week for quick tests, but if something doesn't look right, i'll confirm it with the Tftest kit before I try to adjust anything.

To confirm suggested levels on everything, vinyl pool, pool heater, pool heater manual says:

PH 7.4-7.8
Chlorine 1-5 ppm
Tot Alk 100-200 ppm
Calcium Hardness 100-300 ppm

So, according to other stuff I've read, Alk of 100 is a good target # for my pool, correct?

Pool looks great and current levels are:

Total Chlorine 7 ppm (just adjusted chorinator down a bit)
Free Chlorine 7 ppm
Total Alk 80 (in process of raising to 100)
Calcium Hardness 280
ph 7.2
Cya 60

Thanks for all your help
lbridges
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High Alkalinity, can't keep stable

Postby lbridges » Thu 15 Jul, 2010 16:46

I don't see a reason to raise TA. My readings suggest a TA around where you have it will help slow the rise in pH caused by the effect of the SWG.
chem geek
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High Alkalinity, can't keep stable

Postby chem geek » Thu 15 Jul, 2010 21:21

I agree. In fact, if you find your pH continues to rise over time, you could even let the TA drop to 70 ppm or even 60 ppm and see if that helps. Also, don't try and fight your pH if it settles in near 7.7 (i.e. don't try and drop it to 7.4 or 7.5). You can also consider adding 50 ppm Borates for an additional pH buffer and for mild algae prevention (and some say, a silkier water feel and more shimmer to the water).
Nixon

High Alkalinity, can't keep stable

Postby Nixon » Tue 20 Jul, 2010 23:18

Most likely, the water coming from your hose / outlet is NOT softened, even if you have a water softener installed. Many homes route softened water only to interior fixtures and the hot water heater. Go down to your water entrance and trace out the pipes, see if your hose outlets branch off from the pipes before or after the water softener.

Also, try prestesting your water prior to filling or topping off the pool. Prestest both your hose spigot and a faucet, dont be surprised if you find a difference.

I have been battling hard water alkalinity problems for almost 2 months. It is a sloooooow, painstaking process, and overall alkalinity is still high. Other parameters are all within spec, so I dont worry about it too much...

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