Corrosion question

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Dz7

0
In The Industry
Jun 20, 2016
32
Florida
One of our customers got back from up north and I tested his water. He had a Free Chlorine level of 25 with 0 CYA. I understand this to be extremely harsh and we had the tech that was responsible for maintaining his pool immediately correct the CYA. This is a salt pool mind you. He came back a few days later and told us his heater was completely corroded out and his pump was also victim to high levels of corrosion. The pool levels were maintained properly for the months we were taking care of it until the last month when the CYA was neglected.

He is blaming us for the corrosion and saying it was due to poor water chemistry. Thing is, the corrosion is from the outside not the inside. Also, the part of the heater that was corroded doesn't even have pool water contacting it. The exchanger was fine. Is there any merit to his claims? Is it possible that a month or less with elevated FC and 0 CYA caused this problem? Can that cause corrosion that rapidly?

Hoping chemgeek can weigh in on this one. Wouldn't the corrosion be coming from the inside out if it was from water chemistry? Any input would be greatly appreciated.
 
Rust on the outside would be there regardless of FC level, and Cya in this situation has no bearing at all. I would say that salt water will be more agressive in this situation for sure, but this is not a water chemistry maintenance issue. Not in the least.
 
While an FC of 25ppm and a CYA of zero is certainly harsh and unswimmable, a single excursion like this for a month would not really cause corrosion of the heater and certainly not from the outside in. In general, water chemistry balance is going to cause degradation of the heater core from the inside out. External corrosion of the equipment is more a sign of galvanic corrosion caused by an improper equipment setup, broken bond wire, stray electrical currents, etc.

Of course, your story begs the question - how did the CYA get to zero? That's not possible in one month and so it points to some kind of testing error. Since this is a serviced pool, I would be far more worried about inaccurate testing and over-reliance on dichlor and trichlor causing the pH and TA to crash. But again, that's unlikely to cause external corrosion.

Richard is unlikely to answer this post as he is no longer actively posting at TFP. You could always click on his profile link and send him an email using his external email address. He's usually good about responding to inquiries but I'm not sure he's going to tell you much more than what has already been said.


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Low pH, 7.0 or lower, for a period of time is much more likely to corrode the heater than chlorine. But, as mentioned several times, it would be from the inside out.
 
Over reliance on trichlor and dichlor isn't the problem...it's a salt pool as I stated. Unless the tech was lying about results I assume it was tested correctly although I have no way of knowing for sure. The CYA was tested at 50 1 month prior. Oh actually usually ran high being a salt pool.
 
So why does your client think the corrosion from the outside is a water chemistry issue. That simply makes no sense. Rust would take months to accumulate unless you had some opened muriatic acid around and this heater and pump were enclosed with it.
 
Even so, CYA cannot drop from 50ppm to zero in a month. Simply not possible unless over 75% of the water was drained. You should review your technicians testing methodology.


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Customer has no reasoning behind accusations. He just wants compensation. It is an enclosed outdoor pool. PH actually ran in the 7.6-7.8 range while we were looking after it. No telling what happened before we took it over.
 

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"Enclosed in a screen" pretty much eliminates any theory I had on corrosion on outside of equipment due to any over chlorination/outgassing/fumes buildup.

It wasn't a very good theory anyhow! Just wanted to throw it out there for discussion.
 
Dz7 said:
One of our customers got back from up north and I tested his water. He had a Free Chlorine level of 25 with 0 CYA. I understand this to be extremely harsh and we had the tech that was responsible for maintaining his pool immediately correct the CYA. This is a salt pool mind you. He came back a few days later and told us his heater was completely corroded out and his pump was also victim to high levels of corrosion. The pool levels were maintained properly for the months we were taking care of it until the last month when the CYA was neglected.

He is blaming us for the corrosion and saying it was due to poor water chemistry. Thing is, the corrosion is from the outside not the inside. Also, the part of the heater that was corroded doesn't even have pool water contacting it. The exchanger was fine. Is there any merit to his claims? Is it possible that a month or less with elevated FC and 0 CYA caused this problem? Can that cause corrosion that rapidly?

Hoping chemgeek can weigh in on this one. Wouldn't the corrosion be coming from the inside out if it was from water chemistry? Any input would be greatly appreciated.
Click to expand...

Not sure where you are in Florida but irrigation water from a well can have high salt content and in our area we have learned:

1. If at all possible avoid using spray or rotor irrigation heads near equipment (pool) pads
2. Use drip lines anywhere near anything that can rust (yes galvanized steel will rust eventually)
3. Everything will rot from the salt content of irrigation water, especially if you live near the coast.
 
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