High CYA and CH - The Question To Drain or Not

[bluesmoke]

Hey everyone new member here!

I recently bought a house, and while I wasn't looking for a pool, it came with. The fiancee... now wife also had some say in wanting the pool as well

Anyways, as far as I can tell it was most likely installed back near 1997 and is a Shasta PebbleTec pool with a Shasta TR100 sand filter on it. The pump specs are worn off, but from the lack of controls and standard metal intermatic timer, I have to believe its a single speed. There is an oxidizer, but I've read their worthless and so I left it shutoff like the previous owner left it. I'm near Phoenix AZ and I get sun 365 days a year and our water has high calcium. The previous owner was a pool store devotee by the trichlor puck and phosphate remover cans left behind. I just got my TF100 test kit and the results are below. All tests were done twice to eliminate rookie mistakes.

Fill Water
-------------
FC - 1-2
CC - 0
TC - 2
pH - 7.5
TA - 120-130
CH - 325
CYA - 0
--------------

--------------
Pool Water Taken 2 foot below surface ~70 degrees
Ambient Air 80 degrees (tests performed inside at 78 degrees, water did have a short time to warm)
--------------
FC - 0
CC - 0
TC - 0
pH - 8.0
TA - 160-170
CH - 750
CYA - 100+ (did the dilution and estimated around 150-160, tested outside with sun shining to back, and tested at different times)
--------------


So, the main question I have is should I drain and refill. The pool calculator estimates to fix CYA 60% of water and for Calcium 100% needs to be drained.
I've backflushed the filter 3 times this month and no change in CYA. I just got a hold of the instructions for the filter and I need to extend the backflush time so that may help (was at 2min should be 3-6 min). I believe its really a 9400 gallon pool, but I am going worst case with rectangle at 10K.

I apologize for the FC numbers, I know there is some algae coming, and I am prepared (with liquid CL) to SLAM at FC 45, but I just wanted to see if I should drain first.

Thanks for all your help in advance!

 

[jblizzle]

Welcome to TFP!

Sounds like you have been doing some reading

You definitely want to drain to get the CYA more reasonable. I would drain 75%, retest CYA, and SLAM away.

 

[BoDarville]

Yep...given your pool's CYA level, definitely drain first and then SLAM.

 

[duraleigh]

Welcome to the forum. :lol: Nice work on the tests.

Just reinforcing the others, time for a partial drain and refill. I would do 50% drain first, then retest and do final drain.

 

[Isaac-1]

Same here, I would say drain 50% refill and go from there, you might need to do another partial drain afterward, but it is best not to expose plaster finishes so they can dry out.

 

[bluesmoke]

I apologize for the late update to this thread. Real-life events forced me away for a time, hopefully I will be back around more often now.

Congratulations to jblizzle 75% worked great! I used a harbor freight 1/6hp pump and drained the pool to ~75% over a 20hr period. Then I filled it up with two hoses and the pool fill valve in ~8 hours. Slammed for 3 days straight and no CC's after (.5 after the second day). CYA is 60 and the pool seems to be using a normal amount of chlorine now and looks and feels great.

Thanks for all the help!

 

[soupy8728]

Isn't it amazing how a pool can "feel" great? I've had some friends over since getting my pool in order and all of them have commented on how the water "feels". I've had it compared to silk! Hahaha!

 

[jblizzle]

So did you confirm the SLAM was done by Performing the Overnight Chlorine Loss Test?

 

[bluesmoke]

Yes I did confirm by the overnight chlorine loss test. In this case it was hard to do without that, because near the end of the first day and into the second the CC test was at .5 already.
I wanted to be sure because I had already fought algae once before draining, so I kept it going and the overnight test confirmed it. I even kept the CL higher in the 4th and 5th days just to make sure.

 

[jblizzle]

Sounds good! Congratulations on taking control