What would cause my Ph to test like this?

[jkrupp]

Hi, I am working with a pretty fresh fill (2 week old water) in a 400 gallon covered hot tub, and did have perfectly balanced water. But when I did my complete weekly testing yesterday, my Ph wasn't even on the charts? I have a Taylor 2005 test kit. Here were my numbers 8 days ago:

FC - 5
TC - 5
Ph - 7.6
Alk - 60
Ch - 110
CYA - 30

Since then I tested the chlorine each day, only used the hot tub once, and only added Clorox bleach. Here were my numbers yesterday:

FC - 5
TC - 5
Ph - unreadable. A very bright pink??
Alk - 50
Ch - 110
CYA - a little under 20 (not sure why it fell like that).

Anyone know why my Ph was reading like that? I did the test twice and came back with the hot pink both times. I had thought that would only happen if my FC was above 10, but it has not been above 5.

And on another note, any reason that my CYA dropped like that, in a covered hot tub? I guess that means I have to use dichlor again a couple of times even though I thought I was done with dichlor until the next fresh fill. I DID add about an inch of fresh water (my kids like to splash), but I didn't think it'd make that much of a difference).

 

[JamesW]

You need fasdpd for accurate chlorine testing.

I suspect that your chlorine is probably very high.

Regular dpd beaches out at high fc.

Can you post a picture of the ph test?

 

[jkrupp]

My FC and TC were both at 5, so not very high. It tested at 3.5 on Wed, I added 2 T. bleach. On Thurs it tested 3 so I added another 2 T. bleach. On Fri it tested 3 so I added 3 T. of bleach, so the test of 5 on Saturday makes sense and should be correct.

 

[JamesW]

Are you using fasdpd?

 

[jkrupp]

I'm using whatever came with the Taylor 2005 kit. Based on the Taylor recommendations on this website I went ahead and spent the money on it, so I'd rather not go and buy yet another type of test. But I've been keeping up with the chlorine and have a pretty good idea about how much each tablespoon of bleach will add anyway, so I'm almost positive the 5 is accurate.

I DID just go and test my Ph again (I didn't want to get frustrated by seeing the hot pink again), but to my surprise it is at 7.6. Seems unlikely that it was user error, as I did it twice and came up with the same result? But perhaps an extra drop of Ph regent snuck in there the first two testings? I really have no idea.

- - - Updated - - -

The color on the Ph side was a good match for the chlorine at 10 color on the other side, if that makes sense.

 

[JamesW]

TFTestkits.net

We recommend the Taylor K-2006, not the 2005. You can add the fas test from the link above.

The 2005 has reagents that can bleach out at high fc but should work ok in most cases.

Hot water and aeration can cause ph rise. So, it's not unusual to get a high ph. However, the ph should not go above 8.3 due to aeration or hot water. At 8.3, the ph will be off the chart, but it should not be a crazy high color.

High fc can affect the test and cause it to read way high.

Sometimes the ph test can get erroneous readings. Be sure to double rinse the test vial before and after each test. And mix the ph reagent by inverting a few times.

 

[jkrupp]

Thanks for the information! We are building a pool this Winter, I will upgrade to the fas test you recommend before that I'm sure.

I will just chalk it up to user error then.. I probably did not rinse diligently between the two tests I did yesterday. Hopefully it does not happen again.

Thanks again.

 

[JoyfulNoise]

Your K-2005 has acid demand reagents in it (R-0005). Next time, when your pH is high, use the acid demand drops to see how many drops it takes to get back to a readable range. That can help you diagnose very high pH.