TF-100 pH reading off the scale?

VinceL

LifeTime Supporter
Apr 28, 2012
207
Newton, NC
#1
I have been trying to measure the pH in my pool using the TF-100 test kit. I've been using the TF-100 test kit for several years, and this is the first year I've had this problem. I fear the pH of my pool is totally out of whack.

My first test showed that the color of the sample after 5 drops of the reagent was yellow. It looked more like the reading for the chlorine test. I verified I was using the correct reagent and tested again. I realized I was using reagent from about a year ago. So, I ordered a complete test kit refill. Now that I have fresh chemicals, I tried the test again. I'm still getting yellow. As a test, I took a sample from our kitchen faucet. It tested to 6.8 which seems reasonable. So, the test kit is working.

But, I don't know how to interpret the yellow color when testing the pool water. Does it mean way too high, way too low or unable to determine?

I have a Hayward pH sensor. Initially, it was saying the pH was high at about 8.3-8.4. After putting in some acid, the sensor said the pH was still very high. I brought sensor in, cleaned it, and reinstalled it. The reading came down to 7.4-7.5. But, when I took a sample (from the Sense and Dispense outlet), I got the same yellow reading for pH. The pH sensor is almost 5 years old. So, I've ordered a replacement.

But, I am totally stumped on whether use acid to lower the pH or to raise pH with borax.
 

Patrick_B

TFP Expert
LifeTime Supporter
Jun 7, 2011
14,999
Midland TX
#3
Your pH is low. DO NOT add acid.

You need to raise the pH now or as close to it as possible. Its gone on a while, but this is important. Do you have the products on hand to do it? Borax is good. Please let us know ASAP.

We can addres the probe later, but do not let it control anything yet. Unplug the pump..whatever just take it out of the loop.
 
Aug 24, 2016
21
Las Vegas, NV
#6
If I am not mistaken, very high chlorine level can bleach out results of PH test. May need to dilute test water and retest? Chlorine level high? Slamming?
So I retract my comment as 1) high chlorine over 10 ppm may gave a false purple endpoint and 2) you would add one drop of R-007 to neutralize high chlorine, not dilute.

Phenol red turns yellow at PH 6.8
 
OP
OP
VinceL

VinceL

LifeTime Supporter
Apr 28, 2012
207
Newton, NC
#7
Thanks for everyone's quick responses. I had a done a quick search and didn't find the info about what yellow means in the pH test. And, I've been having Internet problems since yesterday afternoon; the cable guy is supposed to be here at noon.

Last night I added about 7 lbs. of Borax and after about an hour of running the pump got the pH up to between 6.8 and 7.0. I put another 1 lb. of Borax in and ran the pump for another hour. This morning the pH is 7.0. I have another 8 lbs. of Borax on-hand; so I can raise pH further if needed. I'm running the chlorine generator which should raise the pH some more.

Doing some backward calculations using Pool Math, I figure the pH must have been down to around 6.1. The TA is 80 so I'm good there, and the FC is 6 with 0 CC.

The Hayward pH probe is reporting a pH of 10.2 :mad:. It was stored in the house over the winter in its storage module with water in it. But, it is from 2012 so I guess it is past its useful life. I'll have a new one from PoolSupplyWorld next week.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,330
San Dimas, CA (LA County)
#8
Aeration will help drive pH up without affecting anything else. Point the return eyeballs up so you see ripples on the surface. If yours is a spillover spa, run it full blast with the bubbles and everything.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
41,197
Tucson, AZ
#9
So I retract my comment as 1) high chlorine over 10 ppm may gave a false purple endpoint and 2) you would add one drop of R-007 to neutralize high chlorine, not dilute.

Phenol red turns yellow at PH 6.8
You cannot neutralize the chlorine to make the pH test work. The act of attempting to neutralize the chlorine actually affect the pH test and makes it invalid.
 
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OP
VinceL

VinceL

LifeTime Supporter
Apr 28, 2012
207
Newton, NC
#10
Aeration will help drive pH up without affecting anything else. Point the return eyeballs up so you see ripples on the surface. If yours is a spillover spa, run it full blast with the bubbles and everything.
I'm running the spillover with the blower on. Lots of bubbles. :)