cya ?

chip85

New member
May 23, 2007
3
I'm trying to lower my cya in my 25,000 vinyl pool. Currently, the pool is about half empty and my cya reading is 140. Does anyone know a best guess as to what my cya might be if I fill the pool at this point? I know it will dilute some but just not sure how much. thanks

fc - 5.0
tc - 5.0
cc - 0
ph - 7.3
alk - 58
cya - 140
 

DavidD

Well-known member
Mar 29, 2007
91
If your CYA was 140 and you drain half and refill with unstabilized water, your CYA should be around 70......
I say "IF" because a CYA reading of 140 sounds a little suspicious as does the alk of 58 ppm-Sounds pool store-ish :?
Also, be very careful when draining large amounts of water as liners have been known to contract and then bust instead of expand when refilling :shock: . I have always found that replacing water slowly is not only better on the pool (no matter what the type) but also easier on the wallet if you spread it out over two or even more water bills....

Dave
 

chip85

New member
May 23, 2007
3
Just curious as to why the numbers seem suspicious? Do you believe the cya is higher or lower than stated? What about the alk? I noticed the corners of the liner had contracted .....hoping they expand back as a new liner was not in the plan for this year :cry:
 

JohnT

Admin
Mod Squad
TFP Expert
Apr 4, 2007
9,607
SW Indiana
chip85 said:
Just curious as to why the numbers seem suspicious? Do you believe the cya is higher or lower than stated? What about the alk? I noticed the corners of the liner had contracted .....hoping they expand back as a new liner was not in the plan for this year :cry:
The numbers that stand out are the 58 for TA and 140 for CYA. Most TA tests only measure increments of 10ppm, and most CYA tests only go up to 100ppm.
 

DavidD

Well-known member
Mar 29, 2007
91
chip85 said:
Just curious as to why the numbers seem suspicious? Do you believe the cya is higher or lower than stated? What about the alk? I noticed the corners of the liner had contracted .....hoping they expand back as a new liner was not in the plan for this year :cry:
John answered the "suspicions" for me. I would suggest you get a test kit and do your own testing for precisely this reason. Believe it or not, you doing the test will be more reliable than MOST pool stores! 8)

Again, refill the pool slowly and next time, drain less so the corners won't contract. It will take longer to dilute however you have less risk of liner damage.

Dave
 
G

Guest

The numbers may or may not be suspect, depends on just how they were obtained.

The LaMotte waterlink express uses a colorimeter for testing and will test CYA up to 150 ppm (+10 ppm/-25 ppm) and the TA test is +10/- 20 ppm. The colorimeter will read to the ones digit so it will produce numbers like 58 for TA. With the accuracy of this test that means the TA can be as low as 38 ppm or as high as 68 ppm. Also, the computer software (DataMate) does the calculation for adjusted alkalinity, which will be lower than the unadjusted alkalinity if CYA is present. If that is an adjusted alkalinity measure then the TA before correction is in the neighborhood of 110 ppm. If they are using that for testing the numbers are probably close. If it is a strip reader they would be suspect.
 

chip85

New member
May 23, 2007
3
Thanks for all of the advice. So, I guess I need to get a good test kit. Any recommendations? I want to get this cya down so I'll need to test several times. Also, when you say to fill the pool slowly .....how slow is slow?

thanks again .....
 

DavidD

Well-known member
Mar 29, 2007
91
chip85 said:
Thanks for all of the advice. So, I guess I need to get a good test kit. Any recommendations? I want to get this cya down so I'll need to test several times. Also, when you say to fill the pool slowly .....how slow is slow?

thanks again .....
I should have said "drain and refill a little at a time" :oops: meaning don't try to do all of the dilution all at once. Just use a regular garden hose or two to refill and you'll be fine.

Dave