Light corrosion

[Macatthepool]

What is going on with my light?
this light was only in the below ground fiberglass pool for two seasons in Colorado. When the light was removed the water behind the light was black and stinky. Not a septic smell but more metallic. This is the second light I have installed but the first light lasted for several years before it started the same thing.
we have added a ground rod close to the light end of the pool and attached the niche ground to it. We also added a ground wire from the light assembly to the ground rod.
can’t see ant voltages from the pool water to the ground.
comments please.

 

[ajw22]

Welcome to TFP.

That is a Pentair IntelliBrite 5G LED light manufactured on 12/3/2021.

How do you chlorinate your pool?

What test kit do you use?

My guess is your pH is very low causing the corrosion we see.

@1poolman1 may have ideas.

 

[1poolman1]

Fiberglass pool, low pH, and probably lots of trichlor and zero alkalinity. Have seen it many times. Water wants to be alkaline. In a plaster pool, if not "fed" the water will get alkalinity from the plaster. It will go after everything else in the system in a fiberglass or vinyl pool to become alkaline and the metal in lights seem particularly susceptible. Then heat exchangers and the spring on shaft seals.

Have also seen it when a tablet floater is anchored to a dive board which are generally right above a light.

 

[Bill1974]

Also make sure the light is bonded correctly otherwise you maybe making it the above noted issue even worse. If it is ground and not bonded, electrolysis could be contributing to this as well. Checking and correcting the pH and alkalinity are more likely the issues and easier to check and correct.