Brand new pool owner, confused by readings

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N

niilo

Member
May 1, 2024
8
ann arbor, MI
Pool Size
22500
Surface
Vinyl
Chlorine
Liquid Chlorine
Hello! This has been a wonderful resource as I'm trying to learn about pool maintenance - just bought a house with an in ground chlorine vinyl pool and this is our first season. It was just opened by a company, they dumped 1 or 2 bottles of shock in and i filled up the missing water a good 3 feet with the hose (ran for close to 10 hours, given the average of 10gpm of a household hose that's 5400 gallons, or over 20% of the total pool capacity given my calculations). That was 5 days ago and other than skimming and running the pump / filter 4 hours a day I haven't done anything to the pool.

I just got the TF pro test kit but am a little lost how to enter everything into pool math and get something useful back - can someone help me out and point me in the right direction please?

pool:
16' x 34' rectangle vinyl pool; 3' at the shallow end and 8' at the deep end.

current readings:
ph: 7.2
Cl Br: off the charts yellow, darker yellow compared to any available readings
CC: 1
CYA: I stop seeing the black dot before it gets to the 100 line

I don't know what to do with the Cl Br readings.
The CYA levels seem to me i need to replace water, but I just added close to 15/20 % brand new water.

Any info the community can provide would be extremely helpful, thank you!
 
niilo said:
Hello! This has been a wonderful resource as I'm trying to learn about pool maintenance - just bought a house with an in ground chlorine vinyl pool and this is our first season. It was just opened by a company, they dumped 1 or 2 bottles of shock in and i filled up the missing water a good 3 feet with the hose (ran for close to 10 hours, given the average of 10gpm of a household hose that's 5400 gallons, or over 20% of the total pool capacity given my calculations). That was 5 days ago and other than skimming and running the pump / filter 4 hours a day I haven't done anything to the pool.

I just got the TF pro test kit but am a little lost how to enter everything into pool math and get something useful back - can someone help me out and point me in the right direction please?

pool:
16' x 34' rectangle vinyl pool; 3' at the shallow end and 8' at the deep end.

current readings:
ph: 7.2
Cl Br: off the charts yellow, darker yellow compared to any available readings
CC: 1
CYA: I stop seeing the black dot before it gets to the 100 line

I don't know what to do with the Cl Br readings.
The CYA levels seem to me i need to replace water, but I just added close to 15/20 % brand new water.

Any info the community can provide would be extremely helpful, thank you!
Click to expand...
Welcome!

First one: dont use the yellow chlorine test. Thats just for general “do I have chlorine or not” type testing. Use the FAS-DPD. It has powder you add to the sample to make it turn pink and then drops to make it go clear.

Try this on the CYA test. Make your sample with 1/2 pool water and 1/2 faucet water. Then do the test normally. Youll just double the result to get your CYA test assuming its over 100ppm.
 
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Thank you, good to know about the yellow test!

I did the FAS-DPD test, sorry I forgot to post the complete readings there- that test showed 8ppm FC and and a CC level of 1.

I will give that a try for the CYA test, thanks again!
 
What are the TA and calcium hardness readings?

You can do a 50/50 dilution with tap water and retest for CYA to get a better reading and double the reading.

Can you use FASDPD to test the actual chlorine level?
 
For poolmath - do all the tests & enter all your test results first then go to each overview card. There will be target suggestions based on your settings. You can change the targets manually if you wish.
The latest log entry for each parameter will be there as your “current”. So next time if you only need to test & log fc for example that’s the only card that will change.
Note* the ph test is invalid at fc levels over 10ppm
 
Ok, I'm back with some more comprehensive readings:

FC: 8ppm
CC: 1
pH: 7.2
CYA: 120
Calcium: 75ppm
TA: 70

Worried why my CYA is so high after just cycling out so much of the water
 
Welcome to your new pool. It'll seem daunting at first, but once you get the hang of it, it'll become easy peasy.

Pool Math is easy. Once you've setup your pool information, you just hit the + button at the bottom of the home screen, pick 'Log Test Results' and then enter the readings into the boxes as required. You don't have to fill them all out. Once you've entered the ones you have, hit the check mark top-left to store the log. Seriously consider popping for the annual subscription - this allows you to store multiple logs which is very handy (and it's like less than a hamburger...)

If you haven't run a Chlorine test using the drops ( R-0871/R-0870 ), and a CC test using R-0003, then you should - use a 10ml sample, and report those numbers back :)

Your pool would be about 20-21k gallons (rough estimate, but probably good enough for now). Consider adding your other details to your signature/profile, as it'll help people give accurate advice based on your specific setup.
 
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niilo said:
Ok, I'm back with some more comprehensive readings:

FC: 8ppm
CC: 1
pH: 7.2
CYA: 120
Calcium: 75ppm
TA: 70

Worried why my CYA is so high after just cycling out so much of the water
Click to expand...
Your CYA was much higher before adding all the water. You might give it another day and see if it settles. Was the chlorine in the past using trichlor tablets as a source? Those have CYA in them.

Your FC of 8ppm is about right with CYA that high. You’ll want to keep it above 6ppm at all times until the CYA is reduced either by water replacement or time. But if you just refilled the pool, id give it a couple days and retest just to make sure its all mixed in well.
 
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Bperry said:
Your FC of 8ppm is about right with CYA that high. You’ll want to keep it above 6ppm at all times until the CYA is reduced either by water replacement or time. But if you just refilled the pool, id give it a couple days and retest just to make sure its all mixed in well.
Click to expand...
IMPORTANT !!!

Do not use any more Pucks/Tablets or granular chlorine with Dichloro- or Trichloro in the name. These will add MORE CYA to your pool - you don't want that !!
Calcium Hypochlorite is ok (it'll add calcium, but in a Vinyl pool, thats not a huge issue right now).
Sodium Hypochlorite is best (basically, bleach.). Best place around here is Menards - 3.99+tax for a gallon after rebate for 12%.

we're assuming you don't have an SWG or anything like that (hint : include your details in your signature, or snap some photos of your equipment pad and the experts here will be able to tell you what you do and don't have!!)
 
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"Min FC" is 7.5% of the CYA level
"Target FC" is 11.5% of the CYA level
"Shock FC" is 40% of the CYA level
So for cya of 120:
Min fc is 9ppm
Target fc is 14ppm
Shock/slam fc 48ppm
Looks like a water exchange of at least 50% is in your future.
 
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niilo said:
a good 3 feet with the hose
Click to expand...
Ok, so was the pool down to the bottom at the shallow end when they started to refil ?

niilo said:
16' x 34' rectangle vinyl pool; 3' at the shallow end and 8' at the deep end.
Click to expand...
16'x34' = roughly 340gallons per inch - if they put 36 inches of water in, thats 12k+ gallons, or close to 50% of your volume ;)
 
oh you're right - must not have been a full 3 feet because it wasn't totally empty at the shallow end. I ran my hose for ~10 hours to get it to the ideal level and googling it seems a household hose is an average of 10gpm, so around 5400 gallons.
 
The amount of water that was replaced is a bit of a moot point now (IMHO). I think you need to estimate your pool's volume the best you can so that you can plan your next water replacement. For reference: My pool is 18' x 36' with a 8' x 10' spa and a 8' x 20' tanning ledge. 3.5' shallow and 8.0' deep ends. Total volume (according to water meter) is 26,500 gallons.
 
Got it, thanks for all the helpful replies!
And if someone can confirm my understanding - the CYA essentially just makes our FC less effective, right? so the main downside to high CYA is that we'll likely be needing to add more chlorine / bleach to the pool to stay in the ideal FC levels, which means more money. Is there any other downside or harm of the higher CYA levels to people or the equipment?

If we're willing to carefully monitor the FC and spend more on chlorine we could wait until the end of the season for the next water replacement?
 
I suppose you could but I wouldn't. With a target FC of 14 ppm you wouldn't even be able to accurately measure pH (false readings when FC is over 10ppm).
 
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cwswifty said:
I suppose you could but I wouldn't. With a target FC of 14 ppm you wouldn't even be able to accurately measure pH (false readings when FC is over 10ppm).
Click to expand...
@cwswifty can you confirm if false pH readings over 10ppm only affects the testing with the comparator block for R-0014 pH indicator? Or is any pH reading, even from a digital meter, affected by FC being over 10ppm?
 

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