CYA and FC levels in new pool water

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M

Monkmullen

0
Apr 27, 2016
67
Phoenix
I drained and refilled the pool this past weekend. Our CYA levels were sky high and maintaining the pool over the past year was a nightmare, so it needed to be done. Wanted to do it earlier in the year, but just couldn't get around to it until now.

Anyway, we are drained and refilled with new water. I am using the pool calculator to adjust my chemicals. Right now, this is what I've got:

FC: 3
CC: 0
CYA: less than 20 (could still see the black dot until the tube was overflowing)
TA: 150
Ph: 7.5

Regarding the FC level, I've seen two pieces of advice -- SLAM right away, and you don't need to SLAM new water. Right now I'm leaning towards the latter as I don't want to be too aggressive, and I've kept the FC between 3-6. However, with the heat I'm wondering if I should keep that level on the high side.

Also, my CYA is still very low. I've used ~1.5lb of stabilizer so far, left to dissolve in a sock in front of a return. I've added that slowly over three sessions. The pool calculator recommended I use over 2lb, but I wanted to add slowly and again not be too aggressive. But, it's been nearly 24 hours and my CYA is still very low. Should I go ahead and add the remaining stabilizer now, or wait another day and see what my levels are tomorrow? I really don't want to overshoot my target with this one.

So any advice regarding how to address CYA and FC at this stage would be great. Thanks!!
 
You don't need to SLAM Process new water. Especially if it comes from a municipal water source.

CYA is very slow to dissolve and show in the test. Be patient and give it a few days. No reason to rush things.
 
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I agree with ajw and I'll just add a bit :D
Monkmullen said:
I drained and refilled the pool this past weekend. Our CYA levels were sky high and maintaining the pool over the past year was a nightmare, so it needed to be done. Wanted to do it earlier in the year, but just couldn't get around to it until now.

Anyway, we are drained and refilled with new water. I am using the pool calculator to adjust my chemicals. Right now, this is what I've got:

FC: 3
CC: 0
CYA: less than 20 (could still see the black dot until the tube was overflowing)
TA: 150
Ph: 7.5

Regarding the FC level, I've seen two pieces of advice -- SLAM right away, and you don't need to SLAM new water. Right now I'm leaning towards the latter as I don't want to be too aggressive, and I've kept the FC between 3-6. However, with the heat I'm wondering if I should keep that level on the high side.

Also, my CYA is still very low. I've used ~1.5lb of stabilizer so far, left to dissolve in a sock in front of a return. I've added that slowly over three sessions. The pool calculator recommended I use over 2lb, but I wanted to add slowly and again not be too aggressive. But, it's been nearly 24 hours and my CYA is still very low. Should I go ahead and add the remaining stabilizer now, or wait another day and see what my levels are tomorrow? I really don't want to overshoot my target with this one.

So any advice regarding how to address CYA and FC at this stage would be great. Thanks!!
Click to expand...
  • What CYA did you target?
  • Has the pump been running?
  • What is the water temp?
Do you have a vinyl, fiberglass or plaster pool?


Side Point:
  • Your TA is on the high side (not something you have to fret about)
    • since you don't have a SWCG, it should just cause your PH to slowly rise
    • watch your PH (when FC is under 10)
    • and once it gets to 7.8+
    • use PoolMath to add measured dose of Muriatic Acid to lower it to 7.4
 
splashpad said:
I agree with ajw and I'll just add a bit :D

  • What CYA did you target?
  • Has the pump been running?
  • What is the water temp?
Do you have a vinyl, fiberglass or plaster pool?


Side Point:
  • Your TA is on the high side (not something you have to fret about)
    • since you don't have a SWCG, it should just cause your PH to slowly rise
    • watch your PH (when FC is under 10)
    • and once it gets to 7.8+
    • use PoolMath to add measured dose of Muriatic Acid to lower it to 7.4
Click to expand...

CYA Target is 40.
The pump has been running non-stop since yesterday morning around 8, so nearly 24 hours.
I don't know the water temp actually. The thermometer was on the chlorine float, which has been removed from the pool and thrown away. I'll pick up another thermometer today.
And I have a plaster pool with a PebbleTec finish.

PH has been fluctuating between 7.2 and 7.8. I'm keeping an eye on it.
 
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Monkmullen said:
CYA Target is 40.
The pump has been running non-stop since yesterday morning around 8, so nearly 24 hours.
I don't know the water temp actually. The thermometer was on the chlorine float, which has been removed from the pool and thrown away. I'll pick up another thermometer today.
And I have a plaster pool with a PebbleTec finish.

PH has been fluctuating between 7.2 and 7.8. I'm keeping an eye on it.
Click to expand...
Perfect :)
Good!
If you bring the sample indoors to warm up before testing CYA again (I'd wait 48hrs if you think the pool temp is less than 60F), you should get a higher CYA reading (the reagent doesn't react well at less than 60F)
If you could add plaster to your sig, that does affect some of the advice that will be given :)

If you have a way to aerate the pool (pointing returns up), you could do a quick(er) TA lowering if you wanted, otherwise, just monitor as you have :)

Sounds like you have things well in hand! Nice job!
 
Excellent. Thanks for the help everyone.

I've been keeping the PH around 7.5, and the TA is around 140. I've been continuously running the aerator and that's dropped TA a bit. CYA is still on the low side, right around 20, but the water in the test tube is starting to get cloudy, so I'll just keep monitoring that too. I'm also trying to get FC close to 5, but it's pretty much at a constant 3. I'm adding bleach as recommended by the pool calculator, but it seems like it's burning off pretty quickly. Again, monitoring that too.
 
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Monkmullen said:
Excellent. Thanks for the help everyone.

I've been keeping the PH around 7.5, and the TA is around 140. I've been continuously running the aerator and that's dropped TA a bit. CYA is still on the low side, right around 20, but the water in the test tube is starting to get cloudy, so I'll just keep monitoring that too. I'm also trying to get FC close to 5, but it's pretty much at a constant 3. I'm adding bleach as recommended by the pool calculator, but it seems like it's burning off pretty quickly. Again, monitoring that too.
Click to expand...
The CYA might still be low(er), so it's not "protecting" the extra FC from the sun :)
What is your CH? (since you have a plaster pool)
 
splashpad said:
The CYA might still be low(er), so it's not "protecting" the extra FC from the sun :)
What is your CH? (since you have a plaster pool)
Click to expand...

I haven't tested the CH. When I drained the pool a couple years back, the CH was very high. I posted about it and was told that because the water here (Phoenix) is bad, that the CH is always going to be off, and to not really worry too much because there isn't a lot I can do about it anyway. I'll test it again if that info may be useful.
 
Monkmullen said:
I haven't tested the CH. When I drained the pool a couple years back, the CH was very high. I posted about it and was told that because the water here (Phoenix) is bad, that the CH is always going to be off, and to not really worry too much because there isn't a lot I can do about it anyway. I'll test it again if that info may be useful.
Click to expand...
No need, that is true, just curious :)
I think a few forum members in your area test it once a month, to learn when a drain/exchange is needed :)
 
Monkmullen said:
I posted about it and was told that because the water here (Phoenix) is bad, that the CH is always going to be off, and to not really worry too much because there isn't a lot I can do about it anyway.
Click to expand...
That is an odd response. In our area monitoring CSI is very necessary or you end up with scaled up pool.
 
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Monkmullen said:
I haven't tested the CH. When I drained the pool a couple years back, the CH was very high. I posted about it and was told that because the water here (Phoenix) is bad, that the CH is always going to be off, and to not really worry too much because there isn't a lot I can do about it anyway. I'll test it again if that info may be useful.
Click to expand...
This was the exact response: (bold is mine) :D
triptyx said:
Since the only way to reduce CH is to drain and refill (or perhaps an expensive reverse osmosis treatment), and given you're in AZ, you're not going to lower it a whole lot by draining - you don't have a target CH. You simply track it so that you can keep an eye on your CSI number - which will let you maintain your pool balance to prevent scaling (or prevent destroying your plaster)...
Click to expand...
@mknauss will further clarify since he's a "neighbor" ;) better than I can!
 
Right. You need to test CH and monitor your CSI. When the CH rises to 800+ ppm, it becomes very difficult to keep CSI out of the scaling tendency. At that time you drain/exchange to fresh water. That fresh water has ~250 ppm CH. And the cycle begins again. In my area, it takes about 16-18 months. In Phoenix, probably closer to 24-30 months as you do not have the evaporation level I do.
 
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Quick follow up question in case anyone sees this -- I have a pretty large light brown stain on the bottom of the pool where the last of the old pool water ponded when I was draining. It's been over a week now and it's still there, and doesn't seem to be lightening. Should I be concerned about this?
 
What type of pool surface do you have? Can you add that to your signature.

I would think it is most likely organic. Maintaining your FC level in target range should lighten the stain over time.
 
mknauss said:
What type of pool surface do you have? Can you add that to your signature.

I would think it is most likely organic. Maintaining your FC level in target range should lighten the stain over time.
Click to expand...


It's a Pebble Tec. I seem to remember similar markings the last time I drained the pool, only they were primarily along the walls. They did end up going away eventually, but I honestly don't remember if I did anything specific to treat them or if they just went away on their own.
 
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