CYA 150 PPM SLAM POOL and then slowly exchange water

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O

obaro15

0
May 17, 2016
45
Mendon MA
Hi I inherited a pool and adjusted the Alkalinity to 100 pm, pH to 7.6, and hardness to 250ppm. Then I took the CYA reading and found it to be off the chart. I completed the dilution method and estimated the CYA to be 150ppm. I plan to drain and refill my pool slowly over the course of the summer by draining and filling with well water/rain water from my roof. I plan to be diligent and patient until my CYA levels drop to 50 ppm. I realize I need to drain 70% of my pool and drain/refilling will lead to me draining significantly more then 70%.

I know I will need to spend a bit on chems since the FC needs to be kept around 12 ppm at 150 CYA level. I will test repeatedly as the water is exchanged and adjust my FC as the CYA is reduced.

Does this sound reasonable?

Since I just opened the pool I need to shock it at, from what I read, 48 ppm? Do I need to maintain that level as noted in the SLAM procedure? My pool appears to be very clean and algae free, for now...
 
There is no reason to SLAM just because you opened. Only of you have reason to believe there is something in the water.

Remember the pH will not test correctly with the FC greater than 10ppm
 
You can run an overnight chlorine loss test to see it you need to complete the SLAM process.

The FC range for your pool is 11 to 18. Targeting 12 is keeping it at the low end of your range. You will have better results if you keep the FC closer to the top of the range. Dose the pool up to 18 and check it daily to get a feel for how much chlorine it consumes a day. If you target the top of your range and have to skip a day you will be less likely to drop out of range and develop algae.
 
No, you don't have to raise it that high. You can raise it to 10ppm then go test the FC again once the sun goes down. This will be your baseline FC level for the test. Do not add anymore chlorine at this time. Take another sample and test FC at dawn, before the sun is fully up. Compare this dawn FC test to the evening FC test. If you have lost 1.5ppm or more you will need to slam the pool. If your FC loss was less than 1ppm you are good to go! Just raise the FC so it is within the recommended range for your pool.
 
Your OCLT FC level should just a be a "good measure" above your target FC level to show enough loss to call it a success or not. Most folks are around 10-12 for the OCLT since their CYA sits around 40. It was typically done at SLAM levels so it wasn't an issue, but when doing a stand alone OCLT as a test of the pool folks were doing it at regular levels and getting "passes" when there was some algae growth. Hope that makes sense.
 

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I follow your logic. In that case should I dose is significantly higher, say 30ppm?, and see if it holds there? This would eliminate the false pass. If I do have to go up higher does the 1ppm rule still apply for 20, 30, 40, pmm? or it the ppm expected to drop slightly at such high levels.
 
Your pool failed the overnight test. We run the test between dusk to dawn so that FC loss to sunlight is not a factor. Without UV from sunlight breaking down the chlorine, we know that there are organics in the pool and the FC is consumed as it oxidizes the organics.

Your next step is to begin the SLAM process.

One question, do you have an ozone or uv sanitation system on the pool?
 
Using the PoolMath calculator the slam target is 59. You will need to raise the FC to 59 and test the water every couple of hours to raise the FC back to slam level the first day or two of the slam process.
 
I can do that. I also have a significant white scale on the bottom of the pool. From reading through the forums it may be calcium? Before I shock it to 60 I will attempt to get a sample and dissolve it in vinegar to test. All I can say for now is it will not come off via vacuuming or brushing from the surface. Should I address this scale prior to, or after SLAMing?

The picture may not too helpful as it appears as if the water is cloudy, but it is in fact fairly clear, the white material is stuck on the bottom surface...
20160520_055839.jpg
 
I can't help you with the white scale. I can share my thoughts on having had a CYA of 200+. I'd address the CYA first with a water change. Trying to stay ahead of any algae problem with a CYA that high is an exercise in frustration. I have a fairly high water table so it took multiple changes to get my CYA down to a reasonable number. I was afraid to empty the pool due to the high water table. After each change, a SLAM and general maintenance were progressively easier. Take as much water out the first time as you can.
 
Just so you read it again, your CYA is high even for people that prefer high CYA, so you will be in a far less documented and tested area of pool maintenance. Answers to your questions at this CYA could be more vague and open ended than if you were to handle CYA first. That being said, it is your pool and you call the shots.

If you are on Mendon city water we can check the rate on Monday, but back in 2014 it was $9 per 100 cubic feet (roughly 750 gallons). Fun fact: your rate might go down in the next year because they found a significant long term leak recently, after what appears to be years of increasing rates, and it still looks like they buy their water from Hopedale.

Anywho, just for the sake of consideration, let's say your 16x32 pool is just under 4ft deep and an oval totaling 13,500 gallons. To get in terms of how many 100 cubic feet rate charges that would be we do 13,500 / 750 = 18. Then we multiply that by the rate per 100 cubic feet (as of 2014 for the moment): 18 x $9 = $162. Luckily, you don't need a complete drain. Lets say you just did half, since you could easily back wash out more over time to get it where you eventually want it, replacing with free rain water. So that's $81.

I guess I just want to be sure you are making an informed decision to wage this pool care war at such an uncommon and likely annoying CYA. The extra expense in R-0871 FAS/DPD Reagent, using 120 drops per FC test during SLAM testing , which you should do multiple times a day until you pass the OCLT, then still 22-36 drops for your daily tests until you've nailed down your daily FC demand, and then still a couple times a week to verify.

I'm no expert, and I certainly don't know all the facts, for example if you lack a good place to drain water to, or if you have access to very cheap bleach, if you work at a pool store and get free test chemicals, or maybe you use the pool daily and couldn't stand to have it down for a moment. Maybe fill water is of bad quality. Perhaps a more aggressive drain worries you in terms of the in ground pool? Maybe you just don't want to pay for the water mother nature will give you for free. Honestly, as long as you're informed and understand the options and like your choice, I will cheer you on and help when/if I can. I am curious though as to what factors are the biggest motivators to go this route.

Lastly, although not yet a TFP endorsed technique and still very much in the research, development, and refinement phase, there is a method of drain and refill that could potentially appeal to you involving a tarp or temporary barrier between old water being drained and new water filling up. You may read about it here if you would like to see it in action, including photos and video.
 

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