Black stains fiberglass pool bad heat exchanger

plucky71

0
LifeTime Supporter
Apr 18, 2010
117
Michigan
Hello all,

My fiberglass pool is getting black stains. I am pretty sure that it is from the heat exchanger. When I don't run water through the heater I don't get the stains. When I do, I do get stains. I have tested this over a few seasons.

I bought the heater used so I am assuming the previous owner was out of balance for some period of time.

Can I do something to fix/clean the heat exchanger or is replacing it the only option?

Thanks in advance for the help!
 
I could be wrong, but that actually seems like an amazing coincidence.

I'm not familiar with black staining on fiberglass, hopefully someone with
more knowledge will know and post something.

But I'm estimating it is not the heater causing it.
 
Copper can cause black stains. But, I wouldn't think that anything the prior owner did would still be causing the heat exchanger to leech copper into the water. Low pH, below 7.0, will dissolve copper into the water but once the low pH is cured it should stop.

Any other sources of copper? I'm guessing no since you've been here for a loooonnnggg time. :)
 
No other sources. I test regularly and keep everything in spec. Definitely only happens when water is flowing through the heater. As soon as black marks started showing up this season I re plumbed not using the heater. No more new stains. I never even turned the heater on.
 
The only thing I can think of is to rig up a pump and a water tank to try flushing it with some Ahh-some.

What is your CH? Some folks say that CH above 125-150 helps to protect a copper heat exchanger.
 
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