First Test - Question Regarding Additions

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Deily.Bryan

Member
Jun 10, 2019
12
Toms River, NJ
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Double Jewel
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Build Type: Vinyl
Volume: 30000 gallons
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Latest Test Result Summary:
FC: 0.5 (a minute ago)
CC: 0.0 (a minute ago)
pH: 6.3 (a minute ago)
TA: 0 (a minute ago)
CYA: 75 (a minute ago)
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Just got my test kit today and tested our water. pH was off the chart low and TA was zero. Pool had been chlorinated with only tabs and shock by previous owner. CYA is around 75. I used pool math to calculate what we’d need to add to get to correct levels:

6.5 lbs Borax
31 lbs Baking Soda
4 gallons 6% bleach

The pool opened green and looked so bad. The opening chemicals killed everything green and it took quite a bit of work to vacuum(robot) and backwash the DE to get it clear. It looked good for a few weeks but algae growth has started on the liner in the corners, steps, and skimmers.

I am wondering if it matters how I go about adding the above chemicals - can I just put it all in at once or should I work up to the full amounts while testing? Also, with CYA so high will I need to drain any water to get it down or should I be able to maintain FC where it needs to be in order to be effective with CYA as is?

Obviously the pool store said I have nitrates and need to drain my entire pool which is what brings me here. I appreciate any advice and am looking forward to getting this pool cleared up!

Thank you in advance.

Bryan
 
Welcome to the forum!
You can do your SLAM Process with that level CYA but a partial drain and refill would make life much easier. If you can do that drain/refill now, do it. Take it down so that you leave 18" of water in the shallow end. Then refill.
Then mix well and test pH, TA, and CYA again. If pH still not in 7's, use borax to raise it. Assume a ph of 6.8 and target 7.5. Do that repeatedly with testing in between (30 minutes of circulation prior) until the pH is in the 7's. Then add baking soda to raise your TA to 70 ppm.
I suggest you read ABC's of Pool Water Chemistry and consider reviewing the entire Pool School eBook.
 
Thanks for your advice. Should I have a target in mind for CYA?

Also, the test kit states it’s the most subjective test. Does anyone have any input as to when the dot disappears to get an accurate reading? I could see grey at the bottom however the edges of the circle were no longer evident.
 
Best to shoot for 40-=50 ppm CYA.
When you do the CYA test, try this next time.

Once you have your solution ready, back to the sun, etc. Fill the vial to a line, say 80, lower the vial to your waist level and glance for the dot, you see it, add solution to the 70 line, glance, see it, repeat until you no longer see it with a glance. Then use the CYA value one step above the line you read. So if you stopped at 50, use 60 ppm CYA.

The vial is in logarithmic scale. So it is not viable to interpolate between the lines. Just use the whole numbers, such as 50, 40, 30, ....
 
Got it. I got the eBook downloaded and started though it. I will try the CYA test a couple more times and if I’m still confident it’s more than 50 I will drain some water. Once refilled and mixed well I’ll check and correct pH and TA then SLAM reestablishing shock levels of FC a few times. I’ll scrub it clean and then I want to power wash and soak the DE filter socks. Should be set up for a good season. Let me know if I’m messing any of this up! Thank you all.
 
Fully read the SLAM Process article. It is a process. Not adding chlorine a few times.

Not sure I would pressure wash anything. Normal cleaning is sufficient.
 
I read the entire article and it seems like it is basically adding chlorine a few times until the FC is stabilized overnight after it’s done oxidizing contaminates.

I did gather I should wait on cleaning the filter until all the small particles are filtered out. The pool is not in bad shape relative to how it opened however I do want as clean a slate as possible.
 
A SLAM is a process that typically lasts from several days to a couple weeks. Testing your FC and adding liquid chlorine back to shock level FC should be done 2-4 times per day during the SLAM. Once you have crystal clear water, you then do a Overnight Chlorine Loss Test.

Clean your filter when the filter pressure rises by 25% over the clean filter pressure.
 

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I should be able to test and add chlorine 3 times a day before/after work and before bed. I’ll test again 30 minutes after I test and add chlorine at night.

Say CYA is 40 and shock level is 16. Once 16 is maintained overnight what would you anticipate the time frame to be in order to get to maintenance levels and be safe to swim? I’d imagine it needs to come down around 6 FC? Around 5 days if losing 1 FC overnight?
 
106131
Here is a picture of our starting point. I scrubbed the sides so the algae is in the water clouding it a bit. It is taking quite a while to refill from the partial drain. Only took about an hour to pump it out.

We need a new liner next year and I will probably install an SWG at that point. I also hate the shape of the pool but the kids don’t care.
 
Swim now as I can see the bottom of the deep end.

You can safely swim in a pool as long as the FC is above the minimum and at or below SLAM level based on your CYA. You must also be able to see the bottom of the pool in the deep end of the pool.
 
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Seeing some unexpected results from the additions today. It seems the pool volume calculator may have mislead me a bit. The pool is 18x42 with an 8’ deep end and 36” shallow end. It came out to 33,000 gallons. When I look at the effect of adding for what I added the results look like the pool would be 20,000 gallons. Pool Math had me adding 8 gallons of 10% chlorine and I only added 7 thinking I could always add more... curious where I should go from here.
 
Using chemistry effects to fine tune pool volume is generally the best way. Many pools are overestimated in volume.
 
mknauss said:
Using chemistry effects to fine tune pool volume is generally the best way. Many pools are overestimated in volume.
Click to expand...

We just found this out. New pool build...paperwork had it at 23,000 gallons. We figured that was a little high because we expanded our tanning ledge and changed the slope to the deeper end. Called our city water department after we filled, and it was only about 18,000 gallons...that's nearly a 22% difference!
 
Live and learn. I am jumping in quickly so it is to be expected. As far as my levels go; is TA ok at 120? No need to lower it unless pH is creeping up? With FC at 35 I’d imagine that would be pulling pH down. Should I just let the chlorine go and let the sun beat it out? Weather doesn’t look good to swim for a couple weeks at least.

Thanks!
 
TA will resolve itself as you manage pH.
The pH test is invalid when FC is above 10 ppm.
Maintain your shock level FC until you pass all three criteria for a successful SLAM Process
 
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