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Alkalinity Will Not Go Down


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I have a 16'x42" round pool.

Krystal Clear SWG.(not running it until alk under control)

Long story short local pool shop wants to sell $100 worth of chemicals to every customer.

3800 Gallon Vinyl Pool

Hardness-100

CYA-70

PH-7.2

Alkalinity-300

Chlorine-0

Had it tested at local pool shop and they told me to add 2lbs of shock.

Then noted this:

Add 16oz of dry acid to your pool with the pump running to lower your Total Alkalinity. Let the treatment circulate the system then retest in 4 hours.

Your pool may require the addition of an extra 5lbs of dry acid to lower your Total Alkalinity.

Ok so i bought 10lbs of local pool shop brand sodium bisulfate 93%.

Added 1lb 7/18 7am(pump running jet aerated) Result- PH-7.2 ALK-300

Added 1lb 7/18 5pm(pump running jet aerated) Result-same

Added 1lb 7/19 7am(pump running jet aerated) Result-same

Added 1lb 7/20 3pm(pump running jet aerated) Result-same

I am testing with HTH 6 way drop test kit.

I am lost at this point. Any help?

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I believe your pool volume is closer to 4750 gallons assuming 16' diameter and 38" water height (4" from the top of the pool). Nevertheless, if I use your 3800 gallon number, then adding 16 ounces of dry acid to 3800 gallons will lower the TA by 12.9 ppm. So you should have seen it drop certainly after adding 3 pounds of acid.

How are you testing this water? It is somewhat unusual to have fill water so high in TA but not so high in CH (which is Calcium Hardness -- your 100 sounds like it may be Total Hardness so CH would be even less). It sounds to me like your testing procedure is flawed. Are you wiping the dropper tip for the TA titrating drops with a moist cloth before you started your test? If not, then you could have static electricity causing the drops to squirt out and be too small causing you to have a falsely high TA reading. Though any drop-based tests can have this problem, the TA test is most susceptible to static electricity (not sure why since the bottle just contains acid).

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If you are getting measurements from your pool store then who knows whether they are accurate. You should really get your own good test kit, the Taylor K-2006, so you can know the truth and take control of your pool.

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Went outside this morning and the pool was green.

So went to the pool store and they tested and as i suspected the test kit i have is bogus.

Test showed Alk-220 Ph-7.4 Calcium Hardness-200 CYA-60 FC-0.

He informed me to go ahead and turn my SWG back on and start boost cycle.Add 3lbs of powder shock and continue the dry acid.

I went ahead and picked up a new test kit from them. Interested to know what kind of cycle you think i should be running to get this under control?

Again this is an Easy Set round pool with the ring up top 16'x42". Book says 3800 gallons.Running factory filter/pump to a Krystal Clear Saltwater system.

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You need to add unstabilized chlorine to your pool to shock level which with a CYA of 60 ppm (if you believe that number) is around 24 ppm FC. The saltwater chlorine generator will not be able to make chlorine fast enough to kill off what sounds like an algae bloom. You need to get chlorinating liquid or bleach into your pool and raise the FC level and maintain that level adding chlorine frequently if necessary until you kill off the algae.

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No it won't hurt to add bleach, but realize that Leslie's Chlor Brite® is Dichlor and for every 10 ppm Free Chlorine (FC) added by Dichlor it also increases Cyanuric Acid (CYA) by 9 ppm. When you have cloudy water or algae caused by too low an active chlorine level because of a high CYA level, then selling this product is one of the most irresponsible things a pool store can do.

You can use The Pool Calculator to calculate dosages. If you get bleach, make sure it is unscented and NOT splash-less or outdoor. You want plain bleach. Concentrated Clorox is now 8.25% and some off-brands have changed from 6% to 8.25% to compete. Chlorinating liquid is usually 10% or 12.5% and all of these are the same except for their concentration. You can add as much at one time as is needed to get to the FC level you want. Add it slowly over a return flow and then lightly brush the side and bottom of the pool where you've added it.

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Thanks for the reply chem geek.i had found the pool calculator and now on my second shock with the bleach.i scrubbed and vacuumed in between.have got a k-2006 kit with a magnetic stirrer on order to leave leslies to take advantage of someone else.There is one question i have. When do i stop shocking and turn my swg back on to start getting the other chemistry in order? Right now with the test kit(prior to second shock) i am showing Fc-3 Cya-90 Alk-320 Ph-7.4. This help is greatly appreciated.

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You stop the SLAM when you meet three criteria: 1) When your overnight Free Chlorine (FC) loss is <= 1 ppm, 2) when your Combined Chlorine (CC) is <= 0.5 ppm, and 3) when your water is clear with no visible algae.

So a "second shock" means you aren't doing this correctly. You raise the chlorine level and keep adding chlorine to keep it there. If the chlorine drops as it has then algae can grow again. Also, why did your CYA rise form 60 to 90? That doesn't make sense unless you used stabilized chlorine in between measurements. Also, the TA of 320 doesn't sound right. Be sure to wipe the titrating reagent dropper tip with a moist cloth for the test because you want well-formed drops. Otherwise, static electricity can make the drops squirt out and be too small so you'll get an artificially high reading.

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I figured the 2lbs of dichlor the pool store told me to add was the reason the CYA went up that high. I have no algae left and the chlorine level is gradually coming back down. I dont have the new test kit yet so i went to pool store and watched the manager do testing. Results were FC-7.5 CYA-90 PH-7.6 ALK-220 CH-260 SALT-3900.Since CYA and SALT were testing high i decided to drain 1/4 of the water and refill. I am gonna let the pool circulate for atleast 4 hours before testing. I am also in Texas weather and today it is 100*. So im hoping with the sun today plus the drain and refill i will be in the 2-3 FC range with CYA hopefully in the 65 range. I have found mixed results on ideal ranges for this type of pool. What would you suggest putting this pool at? 16' round easy set pool with ring on top water depth 34" using krystal clear swg.

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Ok i got everything but alkalinity under control..FC-4 CYA-60 PH-7.6 CH-250 SALT-3100 ALK-200..ALK started out at 220 and i have added 12oz of Dry Acid 5 times checking to make sure PH was dropping down to 7.0-7.2 each time then aerating water back up to normal. 5 doses have only dropped ALK 20 points. Am i doing something wrong? Pool Calc says it should have dropped 45 to 50.

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It's better to use Muriatic Acid than dry acid if your pool is plaster since a buildup of sulfates from dry acid can damage plaster. I don't know if you are doing anything wrong, but the TA should have dropped more so maybe the TA test is not done consistently or the acid isn't 93.2% sodium bisulfate.

Anyway, for an SWCG pool you should maintain a MINIMUM FC of at least 5% of your CYA level so if your CYA is actually at 65 ppm, then do not let your FC get lower than 3.2 ppm. Your 2-3 ppm is too low a range at that CYA level to prevent algae growth independent of algae nutrient (phosphate, nitrate) level.

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