CH and CYA level?

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henryforever14

Well-known member
Jun 1, 2023
72
Syracuse, NY
Pool Size
16000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Autopilot Digital PPC3 (RC-42)
Last night, I did the OCLT. It was 4.5ppm at 9:30 and 4ppm this morning at 5:30. I think I passed.

I am still somewhat doubtful. I had to be away from home for 5 days last week during which I just let the SWG run at 50% for 13 hours a day. The pool had very low CYA—-just added before I left and I know for a fact, all FC just goes away after sun comes up for a couple of hours.

I am going to do OCLT again tonight.

In the meantime, here is what my numbers are this morning

FC 4
CC 0
CYA <30. I was still seeing the dot at the 30ppm level, although very vaguely. I was doing it in artificial light. It was been cloudy outside recently. When I tested a few days ago, the CYA was at a little bit over 30. Since then, I added about an inch of tap water. This might explain the decline. Since I am still doubtful whether I need to SLAM, I am going to put 10ppm worth of CYA in it today.
CH 150
TA 80
PH 7.5, I can’t tell whether it’s 7.4 or 7.6

Some questions:

1. Yesterday, I put in muriatic acid to lower PH to 7.2 and confirmed at 9:30pm that it was 7.2. I don’t get why the rise overnight.

2. I have an AutoPilot SWG, would you say I should aim at 60ppm of CYA in the long run? My concern is with this high CYA, it would be much harder to SLAM if I ever need to.

3. What CH level I should aim for? I have a heater (which I don’t use…inherited from the previous owner). So, I don’t want the water to be too corrosive. The CSI, with 40ppm of CYA, and my other numbers, is going to be -0.73, which is outside of range. I am aware of how vinyl pools don’t care about CH. But I do have a heater.

Thanks always for everyone’s help.
 
henryforever14 said:
1. Yesterday, I put in muriatic acid to lower PH to 7.2 and confirmed at 9:30pm that it was 7.2. I don’t get why the rise overnight.
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Tough to know. I find the pH test a bit frustrating, perhaps one test or the other was slightly off? Why were you trying to make it so low (7.2)?

henryforever14 said:
2. I have an AutoPilot SWG, would you say I should aim at 60ppm of CYA in the long run? My concern is with this high CYA, it would be much harder to SLAM if I ever need to.
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While we are in different climates, I find my CYA must never be lower than the recommended (min) 60 for best FC retention. I even keep mine close to 80 in peak summer, but again, it's down here in TX. A CYA of 60-70 should be ideal for you.

henryforever14 said:
3. What CH level I should aim for?
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You have no plaster products right? If not, you actually can turn that feature off unless you just like to know for your SWG cell. I don't see a heater in your signature, so basically you really don't need CH at all.
 
Texas Splash said:
Tough to know. I find the pH test a bit frustrating, perhaps one test or the other was slightly off? Why were you trying to make it so low (7.2)?
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I was preparing for a potential SLAM. It is cold recently and will be cold next week also. So nobody is going to swim in there and I thought 7.2 is not going to hurt.

Is 7.6 the deal number to keep in the long run?

Texas Splash said:
While we are in different climates, I find my CYA must never be lower than the recommended (min) 60 for best FC retention. I even keep mine close to 80 in peak summer, but again, it's down here in TX. A CYA of 60-70 should be ideal for you.
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How do you SLAM if you ever need to at 80 CYA?

Texas Splash said:
You have no plaster products right? If not, you actually can turn that feature off unless you just like to know for your SWG cell. I don't see a heater in your signature, so basically you really don't need CH at all.
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I do have a heater. Just updated the signature. Does that change what I should aim for?
 
How does the water look? What's making you a SLAM might be necessary?

I would bump FC to 6 or 7 today and then run another ONCL test tonight.

If you fail, SLAM away. If you pass, I would start to creep up on a CYA of 60. Do it in 10ppm increments over the course of a couple of weeks. That way if you decide next week that you need to SLAM after all, you're not too far gone. And if you get all the way to 60 without having had to SLAM, you should be good to go.
 
henryforever14 said:
It was been cloudy outside recently.
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Light makes a difference...You want to be outdoors in bright sunlight....even overcast is fine.

Very roughly speaking, direct overhead sunlight is around 100,000 lux, strong indirect light (i.e. shaded from the sun) is around 10,000 lux, an overcast sky is around 1000-5000 lux but varies on how overcast (which is why a bright white cloud overcast is still OK), indoors is usually < 1000 even in a bright kitchen (more typically 500 lux).
 
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PoolStored said:
Light makes a difference...You want to be outdoors in bright sunlight....even overcast is fine.

Very roughly speaking, direct overhead sunlight is around 100,000 lux, strong indirect light (i.e. shaded from the sun) is around 10,000 lux, an overcast sky is around 1000-5000 lux but varies on how overcast (which is why a bright white cloud overcast is still OK), indoors is usually < 1000 even in a bright kitchen (more typically 500 lux).
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That makes sense. Will try one more time now.
 
MITBeta said:
How does the water look? What's making you a SLAM might be necessary?

I would bump FC to 6 or 7 today and then run another ONCL test tonight.

If you fail, SLAM away. If you pass, I would start to creep up on a CYA of 60. Do it in 10ppm increments over the course of a couple of weeks. That way if you decide next week that you need to SLAM after all, you're not too far gone. And if you get all the way to 60 without having had to SLAM, you should be good to go.
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Because I was seeing sand/dirt/dead algae on the floor of the pool repeatedly. I vacuum it and it’s back the next day. But, that could honestly just be sand. I took filter apart and discovered a pile of sand in the filter housing. (It’s a cartridge filter. Not sure where the sand is from.) Anyway, I washed those sand away and the pool seems to be staying free of sand.

I was also away from home for 5 days. During the time, the pool sits around 0 FC for much of the day. At night, SWG bumps up the FC. But because I have low CYA and last week was extremely sunny, FC is gone very quickly under the sun.

Between these, I thought a SLAM must be on the way.
 
If you never run the heater, the CH level does not matter. The calcium is only needed for when you fire the heater.
 
PoolStored said:
Light makes a difference...You want to be outdoors in bright sunlight....even overcast is fine.
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This! I, for funsies, have tested this. We recently remodeled our kitchen and have 5000k 1050 lumen LED bulbs in there. 6 of them spaced through the 150-200 sq ft. It’s SUPER BRIGHT by indoor standards. I consistently have tried CYA tests in there. Consistently hit 40 or less of CYA. Then I test outside I’m definitely 50 ppm.
 

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dBsooner said:
This! I, for funsies, have tested this. We recently remodeled our kitchen and have 5000k 1050 lumen LED bulbs in there. 6 of them spaced through the 150-200 sq ft. It’s SUPER BRIGHT by indoor standards. I consistently have tried CYA tests in there. Consistently hit 40 or less of CYA. Then I test outside I’m definitely 50 ppm.
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Well, that was not the case for me. I could definitely see the dot after topping that tube.
 
henryforever14 said:
I was more concerned with the water being corrosive to the metal, not calcium buildup.
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CH level does not relate to the water being corrosive or not to metal. pH does that. For heaters, calcium is related to creating a thin layer of scale on the heat exchanger tubes that protects the metal when the heater is fired. If you never fire the heater, you will not create that thin layer of scale and there is no need to protect the tubes.
 
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mknauss said:
CH level does not relate to the water being corrosive or not to metal. pH does that. For heaters, calcium is related to creating a thin layer of scale on the heat exchanger tubes that protects the metal when the heater is fired. If you never fire the heater, you will not create that thin layer of scale and there is no need to protect the tubes.
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Thanks! That makes more sense now.

How about that CSI parameter? That also only relates to calcium buildup?
 
Correct. You need enough calcium in the water to keep it from foaming. Normally most anything above 50 ppm will achieve that.
 
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henryforever14 said:
I was preparing for a potential SLAM. It is cold recently and will be cold next week also. So nobody is going to swim in there and I thought 7.2 is not going to hurt.

Is 7.6 the deal number to keep in the long run?
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If you maintain TA at 60 ppm, PH will tend to naturally linger between 7.7 - 7.8. I added muriatic acid only once at the start of this season 4 weeks ago.
 

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