PH readings acting strangley

[rmturner54]

I got a strange thing going on with the PH readings I have been taking for the past week. I just happened to stumble on to it when I tested the water and got a low PH reading around 7.2, I retested with the same sample water in the same bottle and the PH 7.8, because I suspected that it wasnt right. I then tested again and again with same water on got 7.8.
Now everytime I test my PH the same thing happens. I have tried taking sample water from different locations with the same results. First test 7.0 approx, all tests thereafter 7.8( with same sample water). I am every careful in rinsing the test tube before and after each test. I gather water from as deep as i can. Could it be an issue with the reagent. It's a year old, been keep in the house in the closet(cool location). Never stored in direct sunlight or outside.

 

[JasonLion]

If it was a reagent problem it would be the same every time. You need to look at what is different the first time from every other time.

I wonder, do you rinse the test vial out indoors with tap water? You presumably don't do that each time in a series of tests.

 

[JamesW]

Are you also rinsing the cap to the vial?

Also, try mixing the reagent by turning it upside down a few times before testing.

 

[gtemkin]

I'm using Tapatalk so if your test equipment information is in your signature I can't see it, so I'm sorry if this is already stated, but this sounds eerily familiar with what happened when I used to use a LaMotte ColorQ tester. Would that be the case here? What tester are you using?

 

[rmturner54]

Yes test kit taylor 2006 in signature. Yes i mixed reagent bottle several times before using. And rinsed top also.

 

[rmturner54]

First thing Monday morning i will try new bottle of reagent

 

[rmturner54]

I rinse with the sample water drawn for testing.

 

[duraleigh]

First thing Monday morning i will try new bottle of reagent

As JL says above, I can't see how that will help. Bad reagent will be bad on every test.....not just the first one.

 

[rmturner54]

Iam almost positive that i prerinse the test tube before putting in sample water. I will test again monday.
Makes sense now that i think about the bad reagent. It would be bad all the time

 

[rmturner54]

Tested this morning. Steps as follows. Rinsed sample bottle with sample water. Drew sample. Rinsed test tube with sample water. Shook reagent bottle vigorously applied drops and took reading of 7.6 to 7.8 first test.
The shaking vigorously is the only difference

 

[Patrick_B]

Ok, good, you could t repeat the different ones as before?

 

[rmturner54]

Its odd that i never had a problem the first year and never had to focus on the testing the PH...just test and log results.

 

[JamesW]

I would replace the reagent. It seems that, for some reason, the reagent is separating and not staying mixed. That would match your results. The first test mixes the reagent when you turn it upside down.

 

[rmturner54]

I will probably buy new reagent. Thats cheap insurance yo mak8ng it right

 

[rmturner54]

update- bought new bottle of R-0004 reagent for PH test. First test w/o shaking up bottle was 7.8, so was second test.
Conclusion-after a year with the bottle stored in a control temp room, the reagent had started to seperate enough to cause first test out of the bottle to be off by 0.4 to 0.6. Have since thrown out old reagent.

 

[rmturner54]

Update again- I double checked my PH readings again just to put my mind at ease. I thought this was fixed. Again first test 7.4, second test 7.8 to 8.0

 

[Patrick_B]

How long is it that you get the higher reading on the pH test? And this is with new reagent correct, or no?

 

[rmturner54]

I don't understand your first question. And yes new reagent

 

[JamesW]

I occasionally get different readings from the first test and a subsequent test. I'm not always sure why this can happen. I would suggest the following:

1) Mix the reagent before testing.
2) Rinse the test tube and cap before and after each test.
3) Test twice to ensure accuracy.
4) Note that the readings can be inaccurate at high chlorine levels.
5) Try using a speed stir to ensure fast and thorough mixing.

 

[Patrick_B]

I don't understand your first question. And yes new reagent

I'm sorry. I meant, how long is it before you run another test and get a new and different reading?