Where is my Chlorine going?

[Adam78]

I am looking for a little advice on the balance of my chemicals…more so the chlorine. I have about a 20,000 gallon in ground pool and use an Inline Hayward chlorinator (right size for the pool and I keep it full). The pump runs about 8 hours every night. Currently my total alkalinity is between 80-100, the ph was a little low 6.8 yesterday but should be back up to 7.2 as of this morning (because I put increaser in last night). The water looks crystal clear…but I started noticing some black staining sporadically appearing on the vinyl liner throughout the pool yesterday… more so in the deep end. I vacuumed the normal stuff off the bottom, but even with a brush the stains would not come off.
That’s when I tested the chlorine level. The kit I use is not the strips, it is called ‘pool trouble shooter’ and it only allows me to test the chorine, Ph, and alkalinity, and involves putting the drops in the little color coded container etc. My chlorine level was 0 when I checked this.
The thing that is confusing me is that my Chlorinator is using up the pucks…actually in what appears to be a pretty fast pace. So I know the chlorine is going into the pool, but I don’t get why it is not showing up on the test... and why I started to get the black stains. After putting in the liquid shock yesterday eve the stains from the bottom are gone this morning. I checked the chlorine levels with the test kit after putting in the shock, just out of curiosity (to rule out whether the test chemicals have gone bad over the winter) but sure enough it turned pink.
So my question is…why is the chlorine from the pucks not registering on the test kit. I keep the chlorinator at about a setting of 4, and like I said it’s flying through the pucks (I keep it full) so I know it’s going into the pool. The water is crystal clear but I started getting that dark staining...which disappeared with liquid shock. I know little about stabilizer… but the pucks I use are supposed to be stabilizing pucks (big tub from Costco).

Thanks in Advance for your help!
Adam

 

[Butterfly]

Hi Adam78 and welcome

Without reliable test results, my guess is that your pool is overstabilized. Those tabs are the cause and also the reason for the pH drop.

If you have done some reading around here, you know we recommend only a few test kits. If you really want to take control and understand your pool, and make it smooth sailing from now on, order one of the test kits. The fav around here is the TF100. Link in my sig.

 

[CeeElGee]

Yeah, Adam, you're probably going to get lectured fairly quickly about using the chlorinator and the trichlor pucks. By now your CYA has to be through the roof, way beyond what is recommended here. Unfortunately the only remedy is partial draining and refilling. And you have to be able to test the CYA.

Short story about my chlorinator: We had an original "blue" Intex for two years and struggled mightily with the SWCG. A year ago during the offseason we made a plan to replace it with something nicer, and after talking with someone from a nearby pool store we planned on using the pucks with a Hayward chlorinator. Even found one on eBay cheap and bought it. Then I found this website and decided to take total control over my water and what goes into it. The chlorinator still sits on a shelf in the garage and I couldn't be happier!