What is this on my zinc anode?

[dustinh]

I’ve researched most of the comments on here, and they are mostly in favor of this being pseudoscience. I have had this pool for 3 years, it’s about 5 years old. I took off the cover of the inline zinc anode and it looks like this.

Should I…

Throw it away and not replace it

Try to scrub it off somehow and stick it back in

Stick in back in as is

Buy a new zinc rod to replace it


Thanks
Dustin

 

[Jimrahbe]

Dustin,

Let's see what Matt has to say.. Calling @JoyfulNoise

I am a firm believer that they are snake-oil...

Thanks,

Jim R.

 

[Newdude]

The National Oceanic and Atmospheric Administration (NOAA) says that fresh water is up to 5000 ppm salinity. Brackish is 5000 to 30,000 and salt water is 30,000.

The ocean tracking folks kinda know a thing or two about salt water, so I personally go with their assessment that your pool is fresh water.

Salt water anodes are a thing, and someone misapplied them to pools who didn't understand the thing IMO.

 

[Bperry]

On the flip side, home water heaters many times have anodes like that. I just replaced a water heater that died from a corroded tank and had a very corroded anode. But it was quite old so I’m not sure how to conclude if it was useful or not.

 

[JoyfulNoise]

Dustin,

Let's see what Matt has to say.. Calling @JoyfulNoise

I am a firm believer that they are snake-oil...

Thanks,

Jim R.

That is what zinc looks like when it corrodes in a saline rich environment - oxides, hydroxides, carbonates, chlorides of zinc metal. It’s basically a big yucky mess of corrosion (that’s a highly technical term there, careful how you use it!). Basically it’s a chunk of zinc rotting away in water … and that’s about all it’s doing. It ain’t protecting squat. But it does have this almost mystical effect of reducing one’s bank account balance when installed … magic I tell ya!

 

[JoyfulNoise]

On the flip side, home water heaters many times have anodes like that. I just replaced a water heater that died from a corroded tank and had a very corroded anode. But it was quite old so I’m not sure how to conclude if it was useful or not.

Completely different process … soft hot water has the effect of leaching metals out of the metal surfaces present. Add a sufficiently soluble mineral like magnesium (which what the rod is made out of) and that will leach rather than any exposed metal surface inside the tank. How much protection that adds is debatable but the industry prefers to have those installed so there’s not much to do about it.

 

[JoelMH]

The zinc looks like it’s doing what it is designed to do. There is a reason why they are called sacrificial zincs in the Marine Industry. My experience is more marine/boating industry than pools. The zinc anode in your picture looks like it is a pencil which is used in marine engines. It threads into a plug that screws into a manifold or block. The zinc’s job corrode before much more expensive engine parts corrode. I assume the same is true for pools.

 

[Jimrahbe]

I assume the same is true for pools.

Joel,

While it makes sense in the ocean, it has almost no useful purpose in swimming pools.

Thanks,

Jim R.

 

[JoyfulNoise]

The corrosion seen on that anode is CHEMICAL corrosion, not galvanic corrosion. It would happen regardless of what the zinc is attached to or not attached at all. It’s not protecting anything, it’s simply chemically reacting with whatever is in the water and then shedding off layers of spent zinc into the water.