new pool in DFW...confused

[nateb]

ok, I'm all over the place. I've started using my test kit and comparing my numbers with my local pool store...numbers are close/same but the range on "ok" are contradictory to pool math. They keep telling me my FC is high. Is there a reason why I targeting number so much higher than my local proveyer of chemicals?

 

[aftrshok99]

Trust your numbers with your TF-100 kit, don't trust theirs as they are hardly ever right. So if they consider 2.8ppm high then what do they recommend your FC to be at?

 

[zea3]

Pool stores do not take the CYA/chlorine ratio into account when determining what is acceptable and what is not. 2.8 FC would be high if you had 0 CYA, however with CYA of 44 (we'll say 40 for the sake of argument) 3.0 would be the minimum amount of chlorine, and ideally the FC should be in the 5-7ppm range. You can see the [FC/CYA][/FC/CYA] shows what the correct ratios of CYA to FC should be.

This is not something we made up and the CYA/chlorine relationship has been known for many, many years, but very few people in the pool chemical industry acknowledge it. New Thinking: Chlorine/Cyanuric Acid In Balance - AQUA Magazine

If you would like to see more threads on this discussion, use the search bar in the upper right corner and use the term CYA/Chlorine relationship.

 

[FattyLumpkin]

Perhaps they're not factoring in / acknowledging the CYA/FC relationship. The higher the CYA, the less effective the same value of FC becomes. Said another way, FC needs to be maintained at a higher level to yield the same sanitizing effect when CYA is higher. However, the CYA is also protecting the FC from being burned off by UV.

At 44 CYA, your 2.8 FC is too low and you risk algae. See the CYA/FC chart in my signature for the appropriate levels.

 

[nateb]

Now that makes sense. I've been freaking out (new pool and all). Surprised they didn't know that. I will act accordingly

 

[nateb]

The chlorine is a and easy fix. And I'll rectify the ph this evening....not really happy about dumping a bunch of water to fix the CH. Can I do that slowly?

 

[zea3]

You can manage high calcium levels without dumping water. You will need to keep the pH in the 7.0-7.2 range and the TA around 70. This will prevent calcium scale from forming. Since this is fairly new plaster high CH is not unusual.

 

[bmoreswim]

Sure on the CH but you can easily manage with a CH of that level. It can go twice that and still be managed by carefully monitoring your CSI. Keep it from -.5 to 0. Never positive or you will likely get scaling or cloudiness if your pH is 8 or above.