Best way to clean light niche and how often?

[33Mike]

I have a fiberglass pool with a Pentair Intellabrite 5G spa light. After a year or so of owning the pool I started to see some rust colored junk on the face plate of the light. I removed the light from niche to clean and unleashed a giant plume of algae. After lots of scrubbing on the pool deck with a brush on the light and using Bar Keepers Friend on the faceplate, I was able to clean everything up and reinstall the light.

I repeated the same process at the start of this season, and I left the light out of the niche during my initial SLAM to start the season. Unfortunately, rather than waiting 1-2 years to clean the light again, within a couple of months I had to repeat the process. Again, there was lots of orange-brown rust colored junk on the outside. When I opened the niche it was completely full of black algae. After cleaning that time, within a few weeks the orange-brown growth has reemerged on the face plate. During all this time I've kept the FC at the high end of the TFP guidance using a SWG.

Questions:

Is such frequent cleaning typical? I'm sure what is happening is that I'm just not getting rid of all the algae. Exponential growth to a noticeable amount takes much less time if there some significant algae to start with.

The Pentair light has lots of nooks and crannies on the backside that I can't get completely clean without disassembling the lens/gasket. Should I just disassemble every time and replace the gasket? What about setting the light in a bucket of bleach water on the pool deck for a couple of hours? I'm reluctant to do this for fear of damaging the light, but maybe others have experience.

Any advice or wisdom is welcome - thank you!

Matt

 

[Texas Splash]

Matt, are you sure everything you are seeing is algae? I ask only because I would've though you would see a significant FC loss or perhaps fail an OCLT with that much algae build up. Plus, the orange-rust colored stuff sounds just like that - rust. If the pH hasn't been exceptionally low to cause corrosion, it almost sounds like an inferior light bracket product to be rusting that quickly.

Let's keep this conversation going to solicit more ideas.

 

[33Mike]

Thanks for the reply. I took out the light again today to further inspect it. For some reason I had in my head that it couldn't be rust. Surely a $100 trim ring would be made of the finest stainless steel available! When I pulled it out of the niche there wasn't any algae behind it but there was plenty of rust-colored gunk on the face plate, especially considering I cleaned it just 2 weeks ago.

Attached are some photos. It looks like rust. In a few place you can see the surface of the face plate appears pitted. We usually keep a close eye on water chemistry. I don't remember the pH ever getting below 7.4 and CSI is usually slightly negative (-0.2 now), but never usually near the -0.6 guidance for the a low limit.

I'd like to replace this and get the rust out of the pool to avoid staining. Is there anything I should know in advance? Looks like I should purchase the face ring, the gasket, and the tension hoop. I assume once I have everything apart I'll be able to clean the lens well.

Thanks again for the the help!

Matt

 

[1poolman1]

Thanks for the reply. I took out the light again today to further inspect it. For some reason I had in my head that it couldn't be rust. Surely a $100 trim ring would be made of the finest stainless steel available! When I pulled it out of the niche there wasn't any algae behind it but there was plenty of rust-colored gunk on the face plate, especially considering I cleaned it just 2 weeks ago.

Attached are some photos. It looks like rust. In a few place you can see the surface of the face plate appears pitted. We usually keep a close eye on water chemistry. I don't remember the pH ever getting below 7.4 and CSI is usually slightly negative (-0.2 now), but never usually near the -0.6 guidance for the a low limit.

I'd like to replace this and get the rust out of the pool to avoid staining. Is there anything I should know in advance? Looks like I should purchase the face ring, the gasket, and the tension hoop. I assume once I have everything apart I'll be able to clean the lens well.

Thanks again for the the help!

Matt

Have you ever checked your alkalinity? Fiberglass pools tend to be very low. Water "wants" to be alkaline. If you don't feed it you see the result, especially if you use tablets.

 

[33Mike]

Have you ever checked your alkalinity? Fiberglass pools tend to be very low. Water "wants" to be alkaline. If you don't feed it you see the result, especially if you use tablets.

Yes, TA has been consistently around 120 +/- 10 ppm. I usually keep the pH around 7.4 and it seems to stay there without the addition of some acid. The higher TA but lower pH put the CSI in the slightly negative range.

I know the TFP suggestion is to have the TA much lower and pH slightly higher. I understand this is done by cycles of lowering the pH with acid and then raising it again by aerating. Maybe I should take on this project.

I've been mainly focused on CSI and I assumed that if CSI was in the optimal range we could avoid corrosion. I do get a fair bit of precipitation (white flakes) from the SWG, so I'd like to keep the CSI as low as reasonable without destroying metals like my heater core.

Matt

 

[33Mike]

Update: I obtained a new face plate, tension, ring, and gasket. I removed the light from the niche and disassembled it. This allowed me to do a bit of a post mortem. It looks like the significant corrosion was on the inside surface where the gasket meets the back of the face plate. The gasket was covered in black goo. Not sure if this was the result of some chemical reaction or some sealer that was applied. In the photo you can see deep pitting in the back of the face plate that has produced a hole all the way through the face plate. I think when this hole finally opened is when I started to see accelerated rust formation on the face plate. Unfortunately, there was similar pitting on the flange of the light itself, but the metal there is much thicker.

I cleaned the flange and reassembled the light. I mated the new gasket to the light and face plate dry (no sealant of any kind). Was that the correct procedure? I don't want to flood the expensive LED light, but it seems to be water tight for now.

Finally, when I reattached the light to the niche, I believe the tab that has the tapped hole broke off from the niche. The brass screw barely began to tighten and then broke free. I see others have fixed this problem with the "pool light wedge." I've ordered one and hopefully I can get that to work.

Thanks again for the help,

Matt

 

[1poolman1]

Update: I obtained a new face plate, tension, ring, and gasket. I removed the light from the niche and disassembled it. This allowed me to do a bit of a post mortem. It looks like the significant corrosion was on the inside surface where the gasket meets the back of the face plate. The gasket was covered in black goo. Not sure if this was the result of some chemical reaction or some sealer that was applied. In the photo you can see deep pitting in the back of the face plate that has produced a hole all the way through the face plate. I think when this hole finally opened is when I started to see accelerated rust formation on the face plate. Unfortunately, there was similar pitting on the flange of the light itself, but the metal there is much thicker.

I cleaned the flange and reassembled the light. I mated the new gasket to the light and face plate dry (no sealant of any kind). Was that the correct procedure? I don't want to flood the expensive LED light, but it seems to be water tight for now.

Finally, when I reattached the light to the niche, I believe the tab that has the tapped hole broke off from the niche. The brass screw barely began to tighten and then broke free. I see others have fixed this problem with the "pool light wedge." I've ordered one and hopefully I can get that to work.

Thanks again for the help,

Matt

In order to maintain the bond for the light, which the screw and mounting hole provide, you can actually run a 1/4"-20 tap in the hole and use a brass screw.
Or, if you want to use a retainer like the light wedge it is better to use this to maintain the bond:

Pool Light Security Clip - Pool Tool # 132-A

The Pool Tool Security Clip is an inexpensive way to fix broken niche tab. It holds pool light in when niche tab is stripped or broken. And it fits all lights. Made with corrosion resistant stainless steel, it is easy to use and can be installed in less than five minutes!Keep one on hand just in...

www.poolweb.com