Fairly high CYA and Chlorine - corrosive to heater?

bmsm6

Active member
Mar 19, 2016
34
NC
#1
Our CYA is 80 and Chlorine at 9ppm, which according to the CYA/Chlorine chart is acceptable I believe. I just spoke with the pool maintenance company who did our initial water/chemicals setup (new build last summer), and mentioned to him our CYA/Chlorine levels and he kindof freaked out that the chlorine was "off the charts". He said that is way too high and is corrosive to the copper pipes in our pool heater (which we only use for the spa occasionally, but the way it is plumbed the water flows through it even when not in use). I do have a bag of bio-active that I'm planning to use to reduce the CYA once the chlorine level goes down, but he also suggested I add some type of metal-out chemical to help prevent the corrosion...I hadn't had to add anything like that before so wasn't sure what that would be. I know there are many knowledgable folks in this forum, so I was curious if you agree or disagree with the corrosion concern? I'm still learning as we haven't had the pool a full year yet. Thanks!
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,327
San Dimas, CA (LA County)
#2
Disagree completely.

When I took over my pool, I had CYA in the 220-240 range. Hard to be more accurate than that when you're diluting 1:3 and 1:4 just to test. I couldn't drain then due to severe water restrictions, so I had to maintain FC up in the 20s. Five years later, my heater -- that has every drop of water that gets filtered run through it -- is still watertight.

I might add that we swam in that 20 FC water with no eye irritation, no smell, and no bleached-out swimsuits. The CYA buffers the chlorine. I don't think I can explain buffering even though I understand it a little from college chemistry, but it's like buffered aspirin. You get the pain relief without tearing up your stomach.

If you search bioactive using the search box, you'll see that the results have been somewhat underwhelming.
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
31,333
Sebring, Florida
#3
The pool maintenance company simply does not understand the effect of CYA. This forum does and has proven it's buffering effect in thousands of pools across the US.

Leave your CYA alone......it's OK for an SWG.......don't let it get any higher, though.

Give that bag of bioactive to someone you really don't like. It doesn't work.
 

bmsm6

Active member
Mar 19, 2016
34
NC
#4
Thanks for the quick responses...I think you're right that they don't understand the buffering effect of CYA...very frustrating. I don't have an SWG; would your opinion still be to leave the CYA alone in that case? That is disappointing about the bioactive...
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
14,515
Tucson, AZ
#7
You can operate a manually chlorinated pool at 80ppm CYA just fine.

What your pool guy doesn't understand is that corrosion is almost entirely dominated by pH and dissolved oxygen levels. There's very little dissolved O2 in pool water and metal corrosion (absent any type of galvanic coupling or impressed currents) typically only starts when the pH gets low, below 7. Chloride sources (salts, chlorinating liquids, etc) enhance certain forms of corrosion and will allow corrosion to occur at higher pH BUT the presence of either chloride or CYA will not initiate corrosion. These guys just simply don't understand the science behind corrosion, they attribute rust and corrosion to the wrong sources and then they spread the misinformation to either appear "smart" or to try to sell you something you don't need...