First spring/summer with a pool

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Z

zylinderhut

Member
Aug 3, 2022
13
Northern Germany
Pool Size
22000
Surface
Vinyl
Chlorine
Liquid Chlorine
Hi guys,

complete novice here, I "inherited" a pool last winter and are doing most things for the first time. The pool was fine last summer, and we uncovered everything two weeks ago.
Unfortunately, the pool is light green throughout, the sides and the bottom are not slimy and don't seem to have a lot of algae on them. So, I think it's time to SLAM.
The liquid chlorine (13%) is on its way and I wanted to double-check with you guys, whether I understood everything correctly.
Here are some quick numbers/parameters:
  • 22.000l overground pool / 4839,324 gallons
  • Sand filter pump (a year old), with a capacity of 8m³/h, set to run for 6h/day when the water is clear
  • ph is at 7.2 (steady for the past two weeks).
  • DPD show that CL (CC?) is between 0,3 - 0,6mg/l as of yesterday (tested with this kind of test: link to picture)
  • CYA is at 50
  • Which makes my slam level 20 - does that mean maintain FC levels of 20? I only have the above test, is there any way I can calculate the right FC levels.

I am located in Germany, and I would be thankful, if you could name a few trustworthy online shops for pool test kits, chemicals etc., if you know of any.
Thanks for your help.
zyl
 
Welcome to TFP! :wave: You are correct, a CYA of 50 equates to an FC level of 20 for the SLAM Process. Perhaps your biggest obstacle may be accurate water testing since I don't believe you have access to a TF-100 or Taylor K-2006C test kit over there do you? I believe there may be shipping restrictions. The link below may have more test kit availability options for you.

Pool Test Kits - Further Reading

www.troublefreepool.com www.troublefreepool.com
 
Correct, I only found the Taylor on amazon and I'm not sure whether it will be a genuine Taylor kit or not. In addition to the one kit I linked above, I also have this . What do you think, does it at least look trustworthy? :) The same supplier also has this one, it's obviously more expensive and I am hesitant to spend the money, because I have no clue what I'm doing exactly.
So, in theory, I'd have to add 3.5l of my 13% liquid chlorine to reach the FC of 20, correct? But from that moment onwards it would kind of be a guessing game.
Thanks for the replies and help!
 
 
Yeah, it just says that the kit is "currently unavailable". Maybe someone else on this forum has experience with the linked kits?
Another question occurred to me while checking CL: do I assume correctly that 1 mg/l = 1 ppm? So I'd need to have 20mg/l FC?
 
zylinderhut said:
I assume correctly that 1 mg/l = 1 ppm? So I'd need to have 20mg/l FC?
Click to expand...
I don't think so. Have you tried using the PoolMath APP yet? It has a menu feature titled "Effects of Adding" that is very helpful when trying to determine dosage amounts. It will compute both Metric and Imperial measurements.
 
Hi guys.
I started my "blind slam" on Sunday. I brought the pool to slam level and on Monday there was an obvious difference. As I don't have access to any suitable tests (read some more threads by the UK members of tfp trying to find some good kits or making do with available ones) I added half a litre of bleach on Monday and again there was a visible impact (top: Sunday, middle: Monday, bottom: Tuesday (1100am)).

20230620_123641.jpg

I know it's not recommended doing it this way, but I don't see any other options at the moment.
What do you guys think? With your expertise, would you say 500ml a day for now is okay?

Thanks you
Zyl
 

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Hi guys, I'm back with an update.
My pool is getting bluer and bluer every day, but sadly we're not at the "clearer and clearer" stage yet. Below are pictures from Tue/Wed/Thu.

20230622_114831.jpg

My question again is: should I change anything as long as I'm progressing in this fashion? Should I add more or less than 500ml/day? Just asking for numbers based on your experience, as I'm still SLAMing blindly

And another question occurred to me:is topping up the pool encouraged or discouraged during a slam?

Thanks so much for your support.
zyl
 
You can and should top-off the water as needed. As for the amount of chlorine, it's your call. The lack of accurate numbers makes decision making challenging at best and questions the efficiency of the process. There's no doubt you are making progress, but still a ways to go. The water should transition from a nice blue color to crustal clear. Whether or not it makes it to that point we simply can't say.
 
Another update:

Pool has become so clear that we can see the bottom! The water is clear, but not _crystal_ clear, so I am SLAMing on. I reduced the daily amount of bleach I add to 300ml on Saturday.

20230625_122709.jpg

Im going to do an oclt Mon/Tue and see whether I can get any accurate numbers.
 
To be not quite as blind during your SLAM you could try to dilute your pool water sample with distilled water (or even tap water if you confirm first that your tap water is not chlorinated, which I think is the case for most of Germany, but I'd still prefer distilled water). With a 1:3 dilution you could test up to FC 20ppm with your comparator block that goes up to 5ppm. You will lose some accuracy (which is already not that great for DPD without FAS), but might still be better than being absolutely blind.

I discussed a while ago testing options with a member in the UK, might be helpful for you:

UK Indoor Pool Refurbishment

Found a few tablets for CH in the Lovibond 5 in 1 set and got a result of ~240. It's a slightly difficult test to get an accurate read on because you keep adding pool water to the re-agent until it quite suddenly changes from violet to pink. I've added 1.6 litres of hydrochloric acid which I...
www.troublefreepool.com www.troublefreepool.com
 
Thank you very much for your input, @mgtfp. I did try the method you described and got realistic readings. I completed the SLAM today with an (albeit inaccurate) OCLT. Yesterday I checked the CC leves, which were close to non-existant and as the water has been amazingly clear for two days, I feel confident enough to end the slam. I will check CYA once I'm back home and then wait for the FC to drop to a safe level.
 
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Probably the last update on this thread. I've got good and bad news:
The good news is that the water is still clear, pH is stable and FC is behaving normally. No algea whatsoever, thanks again!
The bad news is that it has been raining these past days, so I can't really use the pool :cry::p
 
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