Ok what the heck is eating my chlorine?

[watson524]

I had to start a separate thread on this.

Friday, fresh water fill (from a well) after ahh-some, drain, clean, refill, drain, clean, refill.

Adding 1oz dichlor, FC after 20 minutes was 9.0 (at 11pm)

Checked yesterday, 2pm FC was 7.4ppm. Reasonable loss I think

Checked today at 5:30pm, FC = 3.8ppm

Haven't been in it since we drained and filled so no bather waste.

What the heck would eat more chlorine in the last 28 hours than in the prior 15?

This just seems weird to me.

 

[woodyp]

Less clouds, more sun, hotter water, bather load?

 

[ship of fools]

Is it fresh water as of two days ago?? If so then the previous 15 days are irrelevant.

If it is all fresh water then it has no CYA and the chlorine will burn right off.

 

[chem geek]

Did an ozonator turn on? Did the temperature rise?

 

[watson524]

Woodyp - it's covered at all times, unless we're in it at nite, so no sun impact. Haven't been in it, so no bather waste ever in this water. But your temp question is valid. Cold water at fill then warmed up (see below re: my question to chem geek)

Ship - those are hours, not days, so first 15 hours vs next 28

Chem Geek - no ozonator BUT, initial fill temp was 53. Measured FC = 9.0 after 20 minutes. At 2pm the next day (15 hours later), water at 91 degrees, FC 7.4. 28 hours after that, water up to temp at 100F and FC at 3.8

So ok, hotter water uses more chlorine. I forgot about that. I'm going to go measure it again to see what has happened between 5:30pm today when I measured FC 3.8 and now (4.5 hours later). I darn well better see very little to no FC loss.

 

[watson524]

So now we get FC = 3.0ppm. Only 4.5 hours after getting 3.8 so a 21% loss in 4.5 hours??? Is it because of the only 8.1 CYA level that it's eating it quick?

 

[woodyp]

Dose that cya to 30 to 40 range.

 

[watson524]

Going to take some time to build up to that since we'll be using mostly the Nature2/MPS to start but at least if I know this is expected, given the low CYA levels, it'll make me feel better. I did just add 0.5oz of dichlor which takes the FC up by 4.1 and the CYA up 3.8 so 11.9 total accumulated CYA now.

 

[woodyp]

Why not just buy some pure CYA granules from Walmart?

 

[chem geek]

Yes, a lower CYA will have faster loss during the day, but the hotter temperature is also contributing though that loss from temperature would be overnight as well, but not nearly as much as the loss from sunlight during the day.

 

[pooldv]

Tub is covered during the day. Actually, covered all the time when not in use.

 

[chem geek]

Oh, with a tub the hot water would normally have up to 25% FC loss over 24 hours. If it's higher, then there is something it's oxidizing, either something in the well water or perhaps you need to use Ahh-Some in your spa.

 

[watson524]

Did the ahh-some before drain, clean, refill, drain, clean and refill. Possibly the well water I suppose. Any idea what you'd get it tested for? Bacterial contaminates I guess? From the last time we had our well sampled (about 9 years ago) all was fine there with say choloform and the like but I suppose it could have changed.

 

[chem geek]

It's probably not worth testing if you are able to overcome the issues. If you have a persistent problem, then you can check for things like the dissolved organic content, the iron level, and presence of iron bacteria.

 

[watson524]

Ok so for something like this, I should be able to kill it totally off right? I don't want to go to shock level since I want to use the MPS for a while, tho I suppose I could shock with clorox and not raise the CYA so much right off the bat. Iron and Copper are both 0ppm at last check.

Maybe I'm just overly paranoid but my day job is working with data all day every day so I track the numbers closely.

 

[chem geek]

Usually chlorine will get rid of whatever is causing chlorine demand, but not always. While we can test for the most important things in a pool and deal with most of them analytically, there are still some items that aren't measured or handled though they are rare.

 

[watson524]

Ok it looks like things are getting under control. Tested just now (23.5 hours from last test) and FC went from 7.1 (or what should have been 7.1, I didn't test after adding dichlor last nite but let's assume it raised it as much as it was supposed to) to 7.0 so a mere 2% loss over nite.

I'll take it. Tho I am curious about our water now and since my husband works for the state department of environmental protection, I might ask him about getting the water tested somehow (last time we did it he was in the private sector).