Here's and update..
Yesterday:
Pulled fixture completely out. Glad I did. Cable was slimy most of the way.. except the last foot or so. Which makes sense as the conduit is probably below water level till it crosses the pool deck then up to the junction box which is raised above the pool deck off to the side. Now I had an open pipe from pool deck to niche. Decided to pour straight 12% chlorine down the pipe from the pool deck. Probably a half gallon or so in total with some in then chasing some with a hose. Quite a bit more "gunk" was ejected out of the niche. Chased that down with more 12% down the top pipe and let that sit dilute on it's own time.
Also while doing this process grabbed various size/shape small wire brushes typically used in plumbing and cleaning pipes. Mask, snorkle, and a lot of breath holding basically polished that niche. No black stains or anything left got good around where the conduit interfaces to the can and also around the ground lug. It's gleaming shiny now. Even got into the conduit a few inches as far as I could reach. Vacuumed to waste whatever remained on the floor new and old then did a nice backwashing.
Tested at bed time and chlorine was just at shock level. Decided to just leave it there for morning check of OCLT as opposed to "boosting" it to nuclear levels as I had been doing.
Today:
PASSED OCLT! no loss from 11:30pm to 7:30am some minor sun had hit the pool I was only hoping for something close as prior it had been at least a loss of 3 and before finding the light issue was sometimes 6.
Now slight confession is that I've switched to doing the 5ml FC test in an effort to conserve test solution. I've been going through it like mad with no improvement and the shock levels were so high that I needed lots o drops each time. What I'm getting at is there is much more room for error using the 5ml test and looking for a 1PPM tolerance in the OCLT. 1. Now the resolution of the test is in 1PPM increments (1 drop either way) and now your water measurment volume has 2 chances for slight variance error. 1. the pool water fill of 5ml and then the 5ml top off on top of it. Then doing it twice the same (night test, and morning test).. too much chance for error if looking for a one drop or less difference.
I'll let it roll today. I didn't add anything extra but I should only be losing due to sun now in theory. Bring it back to shock close to dark let it mix and test at bed time with full 10ml test. Then test tomorrow morning with 10ml... and then hopefully let it drift down to normal levels and programmer the stenner to add based on whatever new loss rates I determine from the burn off with current temps etc.. Hoping to now be back to acceptable FC demand rates!!
This had to have been brewing for some time.. It's probably never been cleaned out since new. The pool sat as a green swamp for an unknown period (perhaps an entire season not being opened) before we inherited it. It was also a green swamp last year at open. Both years had chlorine demand really spike as temps came up mid summer. Followed by the endless use of lots of chlorine and frequent shocking. This is what drove me to change my approach this year and try BBB getting my CYA in check etc.. was making good headway until the last few weeks where it was like I couldn't add enough liquid to keep up it was quickly apparent that something was hiding.
Yesterday:
Pulled fixture completely out. Glad I did. Cable was slimy most of the way.. except the last foot or so. Which makes sense as the conduit is probably below water level till it crosses the pool deck then up to the junction box which is raised above the pool deck off to the side. Now I had an open pipe from pool deck to niche. Decided to pour straight 12% chlorine down the pipe from the pool deck. Probably a half gallon or so in total with some in then chasing some with a hose. Quite a bit more "gunk" was ejected out of the niche. Chased that down with more 12% down the top pipe and let that sit dilute on it's own time.
Also while doing this process grabbed various size/shape small wire brushes typically used in plumbing and cleaning pipes. Mask, snorkle, and a lot of breath holding basically polished that niche. No black stains or anything left got good around where the conduit interfaces to the can and also around the ground lug. It's gleaming shiny now. Even got into the conduit a few inches as far as I could reach. Vacuumed to waste whatever remained on the floor new and old then did a nice backwashing.
Tested at bed time and chlorine was just at shock level. Decided to just leave it there for morning check of OCLT as opposed to "boosting" it to nuclear levels as I had been doing.
Today:
PASSED OCLT! no loss from 11:30pm to 7:30am some minor sun had hit the pool I was only hoping for something close as prior it had been at least a loss of 3 and before finding the light issue was sometimes 6.
Now slight confession is that I've switched to doing the 5ml FC test in an effort to conserve test solution. I've been going through it like mad with no improvement and the shock levels were so high that I needed lots o drops each time. What I'm getting at is there is much more room for error using the 5ml test and looking for a 1PPM tolerance in the OCLT. 1. Now the resolution of the test is in 1PPM increments (1 drop either way) and now your water measurment volume has 2 chances for slight variance error. 1. the pool water fill of 5ml and then the 5ml top off on top of it. Then doing it twice the same (night test, and morning test).. too much chance for error if looking for a one drop or less difference.
I'll let it roll today. I didn't add anything extra but I should only be losing due to sun now in theory. Bring it back to shock close to dark let it mix and test at bed time with full 10ml test. Then test tomorrow morning with 10ml... and then hopefully let it drift down to normal levels and programmer the stenner to add based on whatever new loss rates I determine from the burn off with current temps etc.. Hoping to now be back to acceptable FC demand rates!!
This had to have been brewing for some time.. It's probably never been cleaned out since new. The pool sat as a green swamp for an unknown period (perhaps an entire season not being opened) before we inherited it. It was also a green swamp last year at open. Both years had chlorine demand really spike as temps came up mid summer. Followed by the endless use of lots of chlorine and frequent shocking. This is what drove me to change my approach this year and try BBB getting my CYA in check etc.. was making good headway until the last few weeks where it was like I couldn't add enough liquid to keep up it was quickly apparent that something was hiding.
