Shelf Life for Cal Hypo 73

mmcwhorter

Silver Supporter
Bronze Supporter
Jul 13, 2015
212
Huntingtown, MD
As I do almost always in early spring.....I opened my approx. 1000 gallon (???) Spa only 2 weeks ago by peeling back the cover over the spa area, pulling the spa return plugs, preparing/priming the filter/pump, and setting the valves to circulate water only thru the spa/filter/heater. Water Temp around 48-53F. I did not backwash the filter, as that was the last thing I did in the Fall when closing the pool. After a few water tests over a couple of days to get the pH / TA / CYA right, I noticed the water didn't smell great as one may expect while we were using the spa a few times.... So I added about 2 oz ounces by volume of Cal Hypo 73% and got it up to >5 ppm. I noticed the CL was pretty strong when we used the spa an hour later.... The Cal Hypo was purchased in spring 2020 and stored in a deck box all winter, outside, we probably never got much below +24 F this winter. I didn't do a CL drop test, but it was strong and definitely above 5 ppm on the Taylor test kit. The next day, it was all gone. Zero....I added Cal Hypo 73 again, about the same amount and it was all gone again a day later. Meaning no change from clear to yellow in the Taylor DPD test kit. It would seem to me the CL should last longer given it's greater than 5 ppm less than 24 hours earlier. I confirmed CYA is about 25-30, CAL= 375, TA at 60, and pH has been inconsistent between 7.2 and >8 (deep purple)......and I have been adding very small amounts of Muriatic Acid to keep it closer to 7.4 while pump running. QUESTION: DOES CAL HYPO HAVE A SHELF LIFE OR STORAGE TEMPERATURE LIMIT ON THE COLD SIDE?. Or is my Spa / Pump and Filter just eating up the CL as it gets rid of all the nasty stuff built up in the system all winter? I'll open the entire pool in 2 more weeks and SLAM it. I hate to SLAM my Spa only LOL.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
39,695
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If you smell chlorine, that is CC. Run the FAS-DPD test of the spa water. Do the FC then CC test.

Cal Hypo will last a very long time if kept dry.
 
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