White crystals on chrome surfaces

scottmcwms

Member
Apr 14, 2023
7
The Woodlands, TX
Pool Size
6200
Surface
Fiberglass
Chlorine
Liquid Chlorine
I have noticed over the past few weeks white crystals growing on the chrome surfaces of my lights. When you brush them off you can see pitting of the surface. Any ideas what would be causing this? The only other metal surfaces in my pool are the stainless screws that hold down the drain cover and the stainless water bond in my skimmer. Neither of those have crystal growth. I don't see it on the white fiberglass, but it would be hard to see.

My water is decently balanced and has been for a while. 50 CYA, FC 5.0 / CC 0.5, pH 7.4, TA 90 (but was 110-130 for the past couple of months), CH 320. I haven't had any major upsets. I have been using a combination of trichlor tablets and liquid chlorine mainly to ensure I don't lost track of the chlorine as I am learning. I plan to move to only liquid chlorine within a couple of weeks. I use dry acid to lower pH as our fill water is close to 8.0. This a brand new fiberglass pool that was first filled around mid-February with municipal water. I do have some iron staining on the whole surface of the pool that I need to address. I believe it is from soil getting into the water during landscaping work. We have a decent amount of iron in our soil. I have not tested for metals but I did the VitC test and it got rid of the stain. I'm trying to think of any other clues you may need.

Thanks for your help.
 

Attachments

  • IMG_4217.jpeg
    IMG_4217.jpeg
    81.4 KB · Views: 4
  • IMG_4219.jpeg
    IMG_4219.jpeg
    165.4 KB · Views: 4
They are from different manufacturers. They aren't a name brand, but I have several friends who also have them and they don't have the same issue. I doubt it is an issue with the pool light.
If you have pitting, it is likely low-quality chrome.

Compare your water chemistry with your friends who have these lights and see what the differences are.
 
If you have pitting, it is likely low-quality chrome.

Compare your water chemistry with your friends who have these lights and see what the differences are.
Basically the same chemistry. We all follow TFP and they are within the normal ranges. I can test for the parameters I mentioned previously but don't have metal or mineral tests. They use MA which is probably the difference. I used dry acid because it was what I could get at the time. Didn't realize it would cause problems.