Chem Question

[tgenre]

Hi guys. This is my first post ever. My pool was completed in November (used chlorine tablets over the winter, and my SWG was never functioning because of the cold water). Once it started to warm up, I basically quit using the chlorine tablets, thinking my SWG would "kick in" - but now I know the chemistry has to be good for the SWG to work (it wasn't) - so my chlorine went down to virtually nothing, and I developed a green pool. I shocked, and it's now beautiful. I am currently testing daily, tweaking the SWG output (trying to reach my Chlorine goal). Throughout all of this, I realized I have a lot to learn, and I found TFP. I got my TF 100 today and tested for the first time this evening. My numbers are:

FC 9
Ph 7.5
TA 70
CH 425
CYA 45

Problems I'm having:
1. My Ph is ALWAYS drifting up. It seems like I could add acid 3 times a week
2. My CYA reading has ALWAYS been around 70 - but this evening read 45.

I'm hesitant to add conditioner, because I've NEVER had a CYA reading this low (pool store OR with the kit the PB included). One (possible) variable, it DID rain heavily this evening (yes, I got the sample from a foot below the surface). What's your thoughts?

 

[JohnT]

Welcome to TFP!

pH climb in a new plaster pool is normal. pH climb in an SWCG pool is normal. Acid demand may drop off some after about the first year.

The CYA test is pretty tough. Check out the videos on the tftestkits site to get confidence in your results. Nothing going on with your water that calls for urgent action, so you can relax and take your time.

 

[tgenre]

Thanks, JohnT. Would rain affect the CYA reading? I planned on giving it a couple of days and retesting to see what I get. I'll check out the videos.

 

[JohnT]

It would take a lot of rain to affect the CYA test.

 

[Isaac-1]

Since the test needs full bright daylight with the sun to your back to get valid results I have to wonder about the test conditions

 

[tgenre]

Thanks. Will retest on a sunny day.

 

[Divin Dave]

I suspect your surprise at the CYA is subject to who previously tested it and how it was tested.
Since this is your first test with your own test kit, then I assume the pool store has been testing it?
Pool store testing is subject to inaccuracy.
Also, CYA is somewhat subject to water temp as I understand it. If prevuously testing was with colder water vs now, then that could also be a bit of a factor in the different test results.

I would recommend you test it a few more times yourself over the next few days to see if its repeatable and if so, then go with that.
test under the same sunlight conditions and perhaps same time of day for the most accurate results.
Water temp as well within a few degrees.

Hi guys. This is my first post ever. My pool was completed in November (used chlorine tablets over the winter, and my SWG was never functioning because of the cold water). Once it started to warm up, I basically quit using the chlorine tablets, thinking my SWG would "kick in" - but now I know the chemistry has to be good for the SWG to work (it wasn't) - so my chlorine went down to virtually nothing, and I developed a green pool. I shocked, and it's now beautiful. I am currently testing daily, tweaking the SWG output (trying to reach my Chlorine goal). Throughout all of this, I realized I have a lot to learn, and I found TFP. I got my TF 100 today and tested for the first time this evening. My numbers are:

FC 9
Ph 7.5
TA 70
CH 425
CYA 45

Problems I'm having:
1. My Ph is ALWAYS drifting up. It seems like I could add acid 3 times a week
2. My CYA reading has ALWAYS been around 70 - but this evening read 45.

I'm hesitant to add conditioner, because I've NEVER had a CYA reading this low (pool store OR with the kit the PB included). One (possible) variable, it DID rain heavily this evening (yes, I got the sample from a foot below the surface). What's your thoughts?

 

[duraleigh]

Hi, tgenre,

Don't add conditioner!!!

Are you chlorinating now with the SWG or manually?
report that back and then I'll have another comment.

 

[tgenre]

Thanks guys! I'm chlorinating with the SWG. I've repeated the tests and I'm getting about 50 (same time of day). I even had my daughter do it. She got 30 once and 50 once. That further added to my confusion!! I've added no conditioner yet.

 

[duraleigh]

Use CYA of 50 for your pool. The test is not accurate enough to give you the precise answer each time but 50 is close enough for what you will do with your pool.

No hurry, but i would suggets you raise it to 70 for your SWG.

In a new pool, pH rises often dramatically. The rate of that rise slows down as a year goes by but you can plan on adding SOME acid to your pool forever.....just not as much as you are having to right now.

FC should be around 5-8 ppm.

 

[tgenre]

Thanks Duraleigh. I'm going to test it again, and maybe add enough to get it to 60, then retest again before I bring it up to 70 (in case I'm messing up the reading!) Out of curiosity, what effect does water temp have regarding the CYA?

 

[duraleigh]

what effect does water temp have regarding the CYA?

In my experience, not as much as we are sometimes discussing here on the forum. I have tested @ 40-50 degrees and at 85 and noticed very little difference.


Nevertheless, the test has 15 ppm inherit inaccuracy (although I am able to get less than 10 ppm consistently...but with nine years practice) so it's a good idea to eliminate all the variables you can. I suggest always test (everything actually) indoors at room temp.