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Can I Add Large Amt Of Baking Soda At Once?


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#1 lovemypool

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Posted 24 September 2010 - 06:01 AM

Can anyone tell me what will happen if I put 10 lbs of baking soda into my 14,000 gallon pool at once? I've read in several places that you should never add more than 2.2 lbs per 11,000 gallons every 4 days. The pool store people say you can dump it all in at once, just make sure you brush it around and get it dissolved. The pool store told me I should try to get my Adjusted Total Alkalinity up before my pool is scheduled to be closed (Oct. 8). Based on my water test yesterday they said add 14 lbs of baking soda and 3 lbs of dry acid (my ph is high too, it seems it's always high, I'm always adding acid).

I'm a total newbie at this (moved into the house early August, and have no prior experience owning a pool) but what I've learned so far is not to trust anything that the guys at the pool store say unless I can verify it to my satisfaction. My CYA and total hardness are also on the high end of the ranges, so I'm wondering if I need to work at draining and refilling some water before we close? The pool store says not to worry since they'll be lowering the water level anyway. So does high CYA or hardness over winter not matter? At the advice of the pool store guy I've stopped using chlorine tabs and switched to granular chlorine instead to keep CYA from climbing anymore.

Here's the results of the water test yesterday:

CYA: 146
Total Chlorine: 2.1
Free Chlorine: 2.1
ph: 7.8
Total Alkalinity: 106
Adj. Total Alk: 62
Total Hardness: 271

Thank you!

#2 dscriterium

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Posted 24 September 2010 - 06:35 AM

While it doesn't hurt to add as much baking soda as you like (within some reason), I see no reason to adjust your TA. TA can vary widely but yours looks perfect around 100 or so. I would leave it where it is.

Secondly, your pH is just a little high but within an acceptable range of 7.2 - 7.8. Again, I would leave it alone unless it goes to 8.0 and then adjust it down to around 7.4

The test results look like a digital readout from test strips. I would not completely trust those results and would get another set from a different source or, best yet, get your own very good kit to test.

Assuming they are correct, the big problem in your pool is CYA. Staying off the tabs is a good start...it should dilute down some over the winter and hopefully, you can start next Spring around 50ppm.

The total hardness is not really important to pools but a component of that, calcium hardness, is what matters. Regardless, you are fine for now. The powder you were sold is probably Calcium hypochlorite which will add calcium to your pool anyway.

All in all, the only large issue with your pool is the excessive CYA. It sounds like you are about to close so it will not harm anything over the winter.

#3 lovemypool

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Posted 24 September 2010 - 07:39 AM

Thank you for your post. I feel better already. On the alkalinity, isn't it the adjusted alkalinity number I need to be concerned about? My understanding is that the total alkalinity test reads both cyanurates and carbonates/bicarbonates, so if you have high CYA, your total alkalinity will read high too, so there is a mathematical adjustment to get to the real measurement of carbonates/bicarbonates, which is what you want at around 100.

Though if alkalinity really doesn't matter much for over winter I won't worry about it and will work on that in the spring when hopefully the CYA will be lower too. My main goal is to get it so nothing bad happens to the pool, pipes or filter over the winter (we are hiring the pool company to actually winterize and close the pool, so I just want to make sure I'm doing whatever is needed to balance the water). Also anything I can do now to make it easier to get the water balanced in the spring I would like to do.

#4 dscriterium

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Posted 24 September 2010 - 08:47 AM

It's the Total Alkalinity or TA that should be in the vicinity of 100. That said, TA readings of as low as 70 and higher than 140 have been reported in perfectly crystal clear pools so you have quite bit of latitude. Anyway, some people do an adjusted test but it is hardly worth the trouble as TA has such a wide acceptable range to begin with. I would leave it right where you are.

If you've experienced a constant pH rise, why don't you lower it to 7.2 before you close? 8.0 or above gets troublesome quickly. Other than shocking before you close (you can read how in Pool School @ troublefreepool.com), that should get you all set for the winter.

#5 lovemypool

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Posted 24 September 2010 - 09:04 AM

Thanks again! The pool has been crystal clear every day since we moved in, so I guess I can stop worrying about the TA.

#6 chem geek

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Posted 24 September 2010 - 10:33 AM

The adjusted alkalinity is only used to calculate the saturation index. If you use The Pool Calculator, this is calculated for you automatically (i.e. it adjusts TA using CYA to get adjusted alkalinity for the saturation index calculation). Using your numbers and assuming 271/1.4 = 194 for calcium hardness (CH) and 80F temperature I get a saturation index of -0.02 which is perfectly fine. Even at colder temps, it will be OK as the pH will rise on its own.

These guys doing your testing don't know what they are doing. Not only are they probably using test strips, but they aren't testing for Calcium Hardness (CH) which is the relevant number needed to calculate the saturation index. Total Hardness (TH) is irrelevant since it includes magnesium that doesn't saturate the water with calcium carbonate.

Please get your own good test kit such as the Taylor K-2006 or the TF-100. You should also read the Pool School for more info on how to manage your pool.

#7 lovemypool

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Posted 24 September 2010 - 10:52 AM

The adjusted alkalinity is only used to calculate the saturation index. If you use The Pool Calculator, this is calculated for you automatically (i.e. it adjusts TA using CYA to get adjusted alkalinity for the saturation index calculation). Using your numbers and assuming 271/1.4 = 194 for calcium hardness (CH) and 80F temperature I get a saturation index of -0.02 which is perfectly fine. Even at colder temps, it will be OK as the pH will rise on its own.

These guys doing your testing don't know what they are doing. Not only are they probably using test strips, but they aren't testing for Calcium Hardness (CH) which is the relevant number needed to calculate the saturation index. Total Hardness (TH) is irrelevant since it includes magnesium that doesn't saturate the water with calcium carbonate.

Please get your own good test kit such as the Taylor K-2006 or the TF-100. You should also read the Pool School for more info on how to manage your pool.



#8 lovemypool

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Posted 24 September 2010 - 10:58 AM

Thank you so much. I've gotten some clues that they don't know what they're doing based on them not being able to explain to me the basic components of the test report output. They use strips and put them into a machine with a photometer and print out a report that has Bioguard all over it (and recommends using lots of Bioguard product). The report calculates a saturation index but no one has ever explained that to me or pointed it out to me, in all the times I've been in the store and have asked tons of questions about the test report. I've looked around at test kits and will definitely get one but didn't know which would be best so thanks for the recommendations. I will check out the Pool School as well to further educate myself. Thanks for all the help!

#9 chem geek

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Posted 24 September 2010 - 02:15 PM

By the way, if you have a vinyl pool with no exposed grout or plaster in contact with pool water, then you do not need to worry about your saturation index being too low. That is, you do not need to worry about having additional calcium added to your water. It is plaster pools that need the saturation index to be closer to zero to protect those surfaces and fiberglass may also need some to protect the gel coat.

#10 lovemypool

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Posted 24 September 2010 - 03:16 PM

Thanks again. It's plaster, in ground. Sand filter and propane heater (which we haven't used much). 14,000 gallons is based on the printed output from the pool store, which is where the previous owners of the house would go to get water tested (and also had these guys open and close for them). So I guess I'd better measure and re-estimate the pool volume, based on how good (not) it appears these pool guys are.

#11 quantumchromodynamics

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Posted 24 September 2010 - 06:02 PM

You can easily add 10 pounds of baking soda to 14,000 gallons with no problem. Just be sure not to add anything else until the baking soda is fully dissolved. You can dissolve 10 pounds in a five gallon bucket and pour it in the pool.

As chem geek noted, your CSI (Calcite Saturation Index) is fine. You do not need to add any baking soda. Please get the calcium hardness tested when you get a chance.

The pool calculator will show you what your suggested chlorine levels should be. With a cyanuric acid of 146 ppm, your FC should be 11 ppm at all times. I know that it sounds high, but the cyanuric acid slows the chlorine down quite a bit and it is no problem swimming at that level.

You should plan to get your Cyanuric acid to less than 80 ppm at the start of next season.
You can't manage what you don't measure. Get a good test kit. I recommend the Taylor K-2006 for chlorine or the Taylor K-2106 for bromine.

#12 lovemypool

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Posted 28 September 2010 - 08:42 AM

Received my TF-100 test kit today and read through the Pool School. Thanks again for those recommendations. The pool store's CYA results were apparently way off. According to that (assuming I interpreted the results correctly), my results are:

TA: 125
Calcium Hardness: 260
CYA: 80
FC: 5.5
CC: 0.5
PH: 7.7
Water Temp: 75

The CH test was a little confusing. Do I stop counting drops when I first detect the color changing toward purple (that's the number recorded above)? It didn't really turn blue until I added 4-5 more drops of the reagent.

I'm glad I didn't add the amount of baking soda recommended by the pool store. I had added 2.5 lbs before posting my question to this forum (and didn't add any more based on dscriterium's first response). With the above results Pool Calculator is returning Saturation Index of 0.21. Is that too high? Also should I shock to get rid of the chloramines? Any further recommendations?

Thanks.

#13 dscriterium

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Posted 28 September 2010 - 11:05 AM

The CH test, the TA Test, FC and CC's test all end in the same manner.

You continue to count drops until there is no further color change, then subtract the last drop from your total count drop.

So an example would be...

drop 18 = still red

drop 19 = still red

drop 20 = starting to turn towards purple

drop 21 = virtually purple

drop 23 = almost all blue

drop 24 = blue

drop 25 = looks just like drop 24....no change

Your calcium hardness would be 240ppm

#14 quantumchromodynamics

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Posted 28 September 2010 - 01:41 PM

Your numbers look pretty good. A CC of only 0.5 isn't too bad. With a cyanuric acid of 80 ppm, you need to maintain a solid 6.0 ppm minimum chlorine level. You could raise your FC to about 10 ppm for a little while to make sure that all of the CC goes away. Liquid chlorine or regular, unscented bleach is the best thing to use to add chlorine to your pool.

If the calcium test goes purple and then takes more than 1 or 2 drops to fully go to blue, it usually indicates metal ion interference. Add 5 drops of the titrating reagent at the beginning of the test, swirl to mix, and then do the test as normal. Be sure to count the initial drops as part of the total needed to make the color change. The titrating reagent is the reagent you add while counting until the color changes. See the video demonstration here. Go to the bottom of the page and choose the video "To Test Calcium Hardness [updated 3/5/10]". Be sure to swirl between drops to get the best results. If you scroll down farther on the same page, you can choose the calcium hardness test procedure for use when metal ion interference is suspected.

A Saturation Index of + 0.21 is good for a plaster pool. Try to stay between 0.0 and +0.30. Your numbers are good for summer, however I recommend that you lower the pH and TA just a bit before closing to avoid scaling over winter. If you lower the pH to about 7.5 with muriatic acid, the TA will also drop a little bit.
You can't manage what you don't measure. Get a good test kit. I recommend the Taylor K-2006 for chlorine or the Taylor K-2106 for bromine.

#15 lovemypool

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Posted 28 September 2010 - 03:32 PM

Thanks for all the help. Is muriatic acid better than dry acid for lowering both the pH and TA? I've been using dry acid to this point.

On the CH test, if I look closely there are tiny red suspended particles which eventually turn to blue suspended particles. Is this how it's supposed to look (instead of just looking like colored water)?

#16 quantumchromodynamics

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Posted 28 September 2010 - 06:37 PM

I prefer muriatic acid. I think that it works better. It is important to make sure that the acid is well dispersed when adding. You can add it into the return stream of a wall return or you can dilute it 10 to 1 in a plastic bucket and pour it in the water. Your pH at 7.7 is pretty good, so you don't want to lower it too much. The main reason to lower it now is because it will tend to rise over the winter. When diluting muriatic acid, always add the acid to the water, never add water to acid.

The suspended particles are another indication of metal ion interference. You should do the modified calcium hardness test procedure. Add 5 drops of reagent R-0012 to the sample at the beginning and swirl to mix. Then do the test as normal. Count the 5 drops as part of the total number of drops of reagent R-0012
You can't manage what you don't measure. Get a good test kit. I recommend the Taylor K-2006 for chlorine or the Taylor K-2106 for bromine.

#17 Concrete

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Posted 01 October 2010 - 11:11 PM

I prefer muriatic acid. I think that it works better. It is important to make sure that the acid is well dispersed when adding. You can add it into the return stream of a wall return or you can dilute it 10 to 1 in a plastic bucket and pour it in the water. Your pH at 7.7 is pretty good, so you don't want to lower it too much. The main reason to lower it now is because it will tend to rise over the winter. When diluting muriatic acid, always add the acid to the water, never add water to acid.

The suspended particles are another indication of metal ion interference. You should do the modified calcium hardness test procedure. Add 5 drops of reagent R-0012 to the sample at the beginning and swirl to mix. Then do the test as normal. Count the 5 drops as part of the total number of drops of reagent R-0012


I like this post. Thanks.




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