Can't explain high chlorine loss

[ti_chris]

I've been having issues keeping the chlorine in the pool ever since the water has been reset after 1.5yr of stagnant water and I've never quite experienced this unless I'm not measuring things right. In the past, I used to add less than half a gallon of liquid 10% chlorine daily and that used to do the trick to keep algae at bay. To be clear, I have no algae problems now either, but I'm dumbfounded by the fact that chlorine just doesn't seem to stay in the pool at all. I've measured my CYA and from what I can tell it seems to be somewhere between 50-60 which is rather high for a pool that's treated purely in liquid chlorine. At about 60ppm, chlorine virtually goes back to 0 after adding a half gallon the next day. I tried shocking it and keeping it high for 24hrs and my baseline was to keep it at roughly 3ppm before adding a half gallon per day (ie: in a ~25k gallon pool). Something doesn't add up here for me.

• I don't see any algae which is good, but I'd expect some given the leafs that fall in there and the virtual lack of chlorine in the afternoon
• A high CYA should keep chlorine around a lot longer than this in my experience.
• pH is around 7.6 right now
• This has been going on for a few months weirdly

 

[PoolStored]

You likely have algae, even if you can't see it.

Do an OCLT. Link-->Overnight Chlorine Loss Test

 

[JessBlount617]

Hey there @ti_chris

Let's do some checking of the things...

1. What sort of test kit are you working with?
2. Algae - you are sure none is hiding in the nooks and crannies?
3. CYA - If you're really between 50-60; you need to shoot for 6 - 9 (and I'd aim high at 9 - in case you have algae you can't see)

What about fill water? Have you tested the fill water source to see if anything wonky is going on with that?

I'm trying to think of all the things that I've run into this season... and see if any of it applies.

Orrrrr go with @PoolStored and run an OCLT - because he beat me to it

 

[ti_chris]

You likely have algae, even if you can't see it.

Do an OCLT. Link-->Overnight Chlorine Loss Test

Yah; might be right. I should definitely test it overnight to get a sense of where that stands.

Hey there @ti_chris

Let's do some checking of the things...

1. What sort of test kit are you working with?

I use a Taylor kit (the one with all of the rare tests that you don't perform very often)

2. Algae - you are sure none is hiding in the nooks and crannies?

It's always possible, but I did go completely nuclear on it for a while to clear all of the heavy algae when I first opened the pool.

3. CYA - If you're really between 50-60; you need to shoot for 6 - 9 (and I'd aim high at 9 - in case you have algae you can't see)

What about fill water? Have you tested the fill water source to see if anything wonky is going on with that?

I'm trying to think of all the things that I've run into this season... and see if any of it applies.

Orrrrr go with @PoolStored and run an OCLT - because he beat me to it

I haven't tested our fill water recently, but the heavy evaporation usually has us fill the pool by 1-2" every week. Our tap water is typically a little high on calcium, but nothing that would really mess with the pool I'd guess. OCLT sounds like a good plan however.