Testing, learning to trust my own eyes

[George N]

I had an interesting day. I had a hard time being sure about my CYA and Ph test levels so I headed to town to get a free pool store water test.
I went to three different stores in two towns (all close to me). Below are all the readings.

Mine
Ph 7.5
FC 4.5
TA 60
CH 120
CYA 30
Bor 50

Store 1
Ph 7.6
FC 3.5
TA 66
CH 190
CYA 68
Bor 58

Store 2
Ph 6.5
FC 4.0
TA 100
CH 150
CYA 90
Bor No test

Store 3
Ph 7.8
FC 5.0
TA 90
CH 200
CYA 40
Bor No test

I didn’t report Salt here as I know it’s slightly low but waiting until I can run the SWCG in the spring.

The one with the FC of 3.5 (Store 1) wanted to sell me some chlorine neutralizer. And stuff to raise the alkalinity. Quote (3.5 can ruin my vinyl over the winter.)

The one with 4.0 Chlorine (store 2) wanted to sell me some something to increase the CH to 200.

I guess I need to trust my own readings (eyes).

 

[duraleigh]

I guess I need to trust my own readings (eyes).

Right on the money! There is no one who cares about the accuracy of your tests as much as you do and, surprisingly, there always seems to be wide discrepancies in pool store testing.

 

[George N]

I can't hardly tell the difference between the 8.2 and the 7.8. I guess I'll keep it in the 7.5
The CYA is hard to tell with or without my glasses but I think I'll manage.

 

[ProPoolGuy]

lol, the different readings kills me. Goes to show the how simple messing up a test can be. SOO many things to pay attention to when doing the test right. One time i kept getting weird alkalinity readings even though all the solutions were new. I was refilling them from larger containers. It was the DPD #9 solution! The sulfuric acid had slowly made a bigger hole and gave everyone low alkalinity readings!

Anyhow, Keep adding a PH reducer until it looks like a nice PEACH color. Slightly red is a little high. Have a women read it, cause men can be color blind to reds. Women can be color blind to Yellow...if using OTO still.
BTW 1-1/3 cups = 1lb sodium bisulfate, careful not to over add. And I think its only 1/4lb for that size pool?? 1/3 cup per dose per 2-4 hours. If you use acid demand, 2 drops = 1 dose.

 

[ProPoolGuy]

btw, store 1 is probably the closest...

You do have low alkalinity and calcium hardness.... Fix the alkalinity for sure. If you really care about your intex pool and plan on having it for years then raise the calcium. Low calcium will damage the liner slowly over time. Chlorine over 4 damage the liner though... ya maybe. Never float tablets, thats for sure, they will slowly kill the liner. Vynl liner manufactures recommend .5-2ppm CL or it degrades the liner. Very tough to always have it there...

 

[duraleigh]

I would leave your pool right where it is. There is little evidence to show that lack of CH is harmful to a vinyl pool. Your pH is fine.

A "peach" color on the vast majority of pH tests would indicate a pH of lower than 7.0....don't do that.

At some point this summer, you may choose to increase your CYA but I would leave your pool alone for now.

 

[George N]

Appreciate all the help. I do plan to leave as is for now then when the temps warm add CYA and salt before turning the SWCG back on. I must say its fun learning all this.

 

[supertune]

Hi George N,
Stay the course with your TF-100 kit!
In my Intex 16 X 48 I had about 110 TA in the beginning, but my PH was always going up to 7.8-8.0
I followed advice from Dave and some of the other mods here (pool school gives a procedure) and lowered it down to 90. My PH now stays steady 7.5-7.6
My Intex pool see's about 65-70% of sun during the day.
My numbers were really consistent most of the summer, with a little up and down with chlorine swinging from always having big pool party's (like every weekend/Pool has been perfect for swimming)
FC averaged 3.5, mostly 3-5 range (up to 7 after some heavy dosing from the party's)
CC was 0 to .5 almost all the time (once or twice I saw 1 but this was in the evening after a big party or the next day after a good dosing)
PH was always 7.5-7.6 if I tested while everyone was in the pool or just after, it read a bit higher but would settle right back the next day.
CH has been between 240-260 every time I checked it (5 or 6 times I tested for it)
CYA 40-45 every time I checked it after getting it in there with a sock and using the pool calculator (used 4300 gals).
My temps were between 80-88*F all summer.

I would think that a little more TA for your pool if your NOT running a SWG and I'm guessing it wouldn't hurt if the CH was up to 200-250, although it has been a general concision here that it's no big deal for my vinyl pool.

Chuck

 

[Richard320]

Trust yourself.

For what it's worth, I have the best luck reading pH by holding it out at arm's length and sorta squinting, so it gets a little fuzzy to where I can't read the black numbers, with a white backdrop some distance behind. In my case, one of those cheap resin stacking chairs.

 

[chem geek]

You do have low alkalinity and calcium hardness.... Fix the alkalinity for sure. If you really care about your intex pool and plan on having it for years then raise the calcium. Low calcium will damage the liner slowly over time. Chlorine over 4 damage the liner though... ya maybe. Never float tablets, thats for sure, they will slowly kill the liner. Vynl liner manufactures recommend .5-2ppm CL or it degrades the liner. Very tough to always have it there...

There was a technical discussion about calcium levels and vinyl in this thread as well as others. The main detriment to vinyl is low pH, not chlorine or calcium. Chlorine is especially not an issue when there is CYA in the water that significantly lowers the active chlorine (hypochlorous acid) level.