Getting started

[discreet_mayor]

Hi!
I've owned a pool for about 10 years now, but have only used test strips to keep an eye on water quality. My track record is spotty

This year, more as a learning experience and for the pleasure of it, I designed my own pool monitoring / chlorine injection system (uses sodium hypochlorite at 10.8%). ORP and PH probes are well-calibrated (orp reads 470 mV in 470 mV solution, ph reads 7 & 10 in respective solutions).

I am now suddenly exposed to how much stuff is going on in the water, and find that I need advice from more experienced people to keep things in check.

Had a water check done yesterday morning at 10:00:

Volume is roughly 10,000 gallons
Free chlorine: 1.54 ppm
Total chlorine: 1.76 ppm
CYA: 29 ppm
PH: 7.6
TA: 96 ppm
Calcium: 190 ppm

Here, at 11:00 I am adjusting PH down by adding "PH minus", presumably some acid, in crystal form, to bring PH down to 7.5 or so.



What is surprising to me is that it has climbed back up to 7.8 or so overnight. Water jets were oriented upwards, which I suppose could introduce air, and increase PH. Blue marker is when I oriented them down. So, that's question 1. What else could explain this?

Now ORP:

Test strips indicate 1PPM chlorine at the moment (added 250 mL chlorine yesterday evening, water currently registering at ~686 mV ORP). I am thinking it's maintained through the night, then sunrise and chlorine breaks down (?):



So, again, in short, just want to double check that this makes sense, and get some advice on PH observations/management.

Thanks!

 

[cowboycasey]

Welcome to TFP

I do not and have never used ORP... But I have read using PH minus or dry acid is harmful to the sensors.. You should only be using Muriatic acid to drop PH..

Test strips... or we like to call them guess strips, who knows what you have as you can not trust them, they are not worth the money you spent on them...

FC at 1 with a CYA at 30 if that is actually what you have is way to low to keep your pool clear from algae... FC/CYA Levels

I would recommend you get a Taylor K-2006C and start testing your water so you and I and everyone here can know exactly what is going on and we can all help you to keep a TFP clear pool..

 

[Mike1162]

Your chlorine level is too low. I'd go add a half gallon of your 10.8%.
We don't trust test strips. You should order one of the recommended test kits.
Test Kits Compared

 

[discreet_mayor]

OK, so yeah, 1 ppm seems low, but the oxidation potential is high, which adds some confusion. The probe indicates all's well in terms of disinfection (and as stated, I calibrated it well a couple days ago). What are your thoughts there?

I guess I'll keep an eye on readings and add chlorine, remeasure.

Thanks for the tip on muriatic acid - will do that.

 

[Mike1162]

Here's three short articles that will help you maintain a trouble free pool.
Chlorine/CYA Chart
Overnight Chlorine Loss Test
Shock Level And Maintain

 

[discreet_mayor]

Excellent, thank you. Noted.

I failed to mention there's a small ozonator in use, I suppose it could explain higher than expected orp.