Odd winter test results

Johnny B

LifeTime Supporter
Mar 19, 2009
574
Charlotte, NC
Date 1.20.2019 51days since Last Test and treatment with acid & chlorine,
19,381 gal is the current winter/closed volume

pH 7.9; Target pH7.7 (not 7.6 because 7.6 is corrosive ) with 6oz acid
FC 3.5 Target 8; gave it 242 oz 6% Bleach
TA 50 with a 25ml sample so Target 70 with 5.6 lbs say 5 lbs, only gave 4 lbs
CH closing Target400 so assume some dilution say 350- 375
46° F
CSI: potential corrosive to plaster, but a CH of 375 is balanced & is likely, if pH7.7 & TA is 70 then balanced

Date 1.24.2019 3days since Last Test
19,381 gal

pH >8.2 which is suspicious unless above TA change / baking soda does that, Target pH7.7 (not 7.6 because 7.6 is corrosive ) with 16oz acid, play it safe, say Target 7.9 with 9 oz say 10 oz acid then re-test the pH in a few hours (or should it be days? Or weeks? If weeks then I will not add the aforementioned 10oz acid, so I am awaiting your suggestions )
FC 8.0
TA 70 so leave, do not add that 5th lb mentioned above
CH Sept closing Target400 ; CH tested 190 today
46° F
CSI: potential corrosive to plaster, but a CH of 375 is balanced & is likely, if pH7.7 & TA is 70 then balanced.

CH has always held over the winters, when I open in spring the CH is in the 325 range.
Yes I wait until the sample water is room temperature. Yes the reagents are fresh & stored inside room temperature in a cabinet. Yes, I circulate the water with a brush before & after getting a water sample & after chemicals are added ( and I waited 3 days between tests).
1- You guys want me to bring the CH up to my closing level 400 range? Something doesn’t seem right with the CH. I have no issue adjg the pH & FC & TA, but the CH is weird, no? Yes, weve had plenty rain so dilution but not too different than previous winters,. I don’t think I ever felt compelled to test CH in previous winters because it always held until spring. I”ll open in late May. My plaster is in bad shape & will re-plaster only when forced to, does that make a difference ? (hasn’t the previous winters)
2 - If ph changes take weeks at this water temperature then I will not add the aforementioned 10oz acid till I hear from you
Thanks
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
"If" your CH is truly about 175 your plaster is fine (CSI balanced @ about -0.16) IF you let the pH ride up to about 8.0. I would do that. It's easiest to do and the quickest to adjust once the water temps increase later. I know the pH can be hard to read (purple shades) at about 8.0 or more but keeping it at 8.0-8.2 will work in your favor.

As for the odd CH drop … well … we know CH doesn't just disappear. I'm sure the CH could drop a little from winter prep and follow-on snow/rain but unless you had a significant water exchange it might simply be a testing issue. If you still show 175 in the spring you might look closely to ensure there are no slow leaks around. Hope that helps.
 

Johnny B

LifeTime Supporter
Mar 19, 2009
574
Charlotte, NC
Thanks. Yes, that helps. I just have to believe the CH is in the 325 probably 350 range, and CSI is still balanced at a CH350.

I worry about CSI in winter because my plaster corroded ; I was told here on TFP because “the the pH was too high for too long”.
I see that I remain balanced at pH 7.9 with CH at both at 190 & 350, so I think I will drop pHto 7.9 since it always creeps up, otherwise I’ll have to retest too soon, and as you say pH is hard to read in the 8.2 range. You guys are ok with that?
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
I worry about CSI in winter because my plaster corroded ; I was told here on TFP because “the the pH was too high for too long”.
Johnny, just to clarify that statement ………. plaster corrosion occurs when the pH and/or other CSI factors drop too LOW for an extended period of time. When the pH gets too high (typically in the summer w/warmer water) that's when scale occurs. The colder water temp is your challenging variable for now that is pulling the CSI a bit low. Hence maintaining a slightly higher pH level.
 

Johnny B

LifeTime Supporter
Mar 19, 2009
574
Charlotte, NC
Thanks to you both.
I may have misspoke, scaling, not corrosion. But my plaster is old & needs re-doing either way/ no matter what my condition is, I'm delaying it as long as I can.

Also, as a newbie yrs ago, I may have misunderstood what the TFP pro was helping me with. The issue back then was: my first winter, I never tested nor treated the water (because wife never did before me). Opened in spring & had the plaster scaling, attributed to CSI being off too long during the winter, “most likely pH too high for too long”, and I may have that wrong, but that is what I recall, hence my concern over the winters with pH & TA & chlorine (never had to fiddle with CYA nor CH, don’t even test those in the winter). All winters thereafter, I test & treat all winter and be sure CSI is balanced.

Thanks again for your help. I didn’t even bother to check CSI on PoolMath with a CH of 190 at a higher pH- CSI is fine. I just had in my head “I always drop the pH to 7.6 or 7.7 & know it creeps up” plus had the worry of “pH too high for too long”, but as you point out I can stay in the pH 7.9-8.2 range no problem.