Getting chemistry right on Intex Krystal Clear SWG system?

Jun 24, 2012
Hi, I just set up an Intex 16' round Ultra frame pool. It has the Krystal Clear Salt water system. Capacity is 5,000 gallons. I put in 120 lbs. of salt and ran the pump for 24 hours as per the manual. I then got the SWG running at the 2 hour/day interval. I tested it after this for copper level and chlorine and had nothing so I ran the boost cycle which is 8 hours of the SWG and then retested. It seemed like the copper went up a little but I am still getting nothing on the chlorine test. I am using the HTH 6 way test kick which I guess is not the best but it is all I have right now.

I added 1.3 lbs of cyanuric acid. When tested I am not getting anything. The vial fills all the way past the 30ppm and the black dot does not fade at all. I have read on here that it can take a week to get an accurate reading on CYA though.

My other readings are: TA-90, Hardness-70, pH-about 7.2 and not a hint of yellow on the chlorine so I don't know where I am at there.

The water is clear but there is a slick film on the sides and bottom of the pool. My question is how should I proceed with getting the chemistry right? The Intex manual says free chlorine should be between .4 and 1.5 ppm which is quite a bit lower than the 3-5 recommended on this site. Although I guess SWG pools run a lower chlorine level. Do I need to get my pH up a bit? Do I need to add chlorine or just run the boost function again? I am unsure on how best to proceed and would greatly appreciate some direction. Thanks a lot.


Well-known member
May 6, 2012
Peoria, IL
Re: Getting chemistry right on Intex Krystal Clear SWG syste

First of all, get one of the three recommended kits on this site, because the chlorine reading your getting with your kit measures total chlorine (Free chlorine + combined chlorine = total chlorine). Given that you have algae, any level measured with your kit is likely to be all CC. Secondly, an SWG is meant to maintain a constant FC level by slowly generating chlorine, but to first get it to your target level, you need to use bleach. It's unlikely that your SWG will be able to bring your FC to target level from zero by itself, especially in the middle of summer. But since you say you have algae, your going to have to bring your FC to shock level and hold it there until you pass the overnight losss test, have a CC of .5 or lower, and clear water. See "How to Shock Your Pool" in Pool School on this site. Once the shocking process is complete, let the FC come down to target level and then use your SWG to hold it there. I would run it for an hour more than what the manual says to maintain a level of at least 2, preferably 3 or 4. Also, you probably don't need to raise your pH because it will most likely rise naturally due to the aeration from your SWG, so be prepared to lower your pH a few times a week. As for the CYA, is does take at least a week after it has fully dissolved to show up on the test. I would suggest you thorougly read Pool School on this site and get one of the recommended test kits. Good luck.

Edit- Also, be sure to brush the whole pool at least once a day during the shock process. The film you describe is a protective layer that the algae grows, so you will need to brush it thoroughly to expose the algae to the chlorine. Otherwise, the chlorine will have a tough time killing it, even at shock level.


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TFP Expert
May 7, 2007
Silver Spring, MD
Re: Getting chemistry right on Intex Krystal Clear SWG syste

Take a look at Pool School article on Water balance for SWGs. There are also several other articles in Pool School that are worth reading.

CYA can take some time, up to a week, to fully dissolve and show up on the test. However, you only added enough to raise the CYA level to around 30, which is right near the lower limit of what the test can measure. The recommended CYA level for use with a SWG is between 70 and 80.

Until the SWG can keep up with your chlorine demand, you need to add some chlorine manually.
Jun 24, 2012
Re: Getting chemistry right on Intex Krystal Clear SWG syste

So even though the pool water is nice and clear that slippery layer on the sides and bottom is beginning algae growth? Also with the CYA, I added what the Intex manual suggested for startup (1.3 lbs.). Should I at least add the rest of the bottle? It was a 2 lb. bottle. I was a little paranoid about adding too much CYA because I did not want to drain the pool down.

The pool school numbers for SWG pools (especially the chlorine level) are different than the Intex manual. Should I disregard the manuals numbers and shoos for the pool school SWG numbers? Thanks for your help.