Zero CYA

Southern Swimming

In The Industry
Oct 21, 2020
11
Hi all,

I posted several weeks ago regarding CYA dropping rapidly over the course of a few weeks. I am running into a new issue that I would like advice on.
I picked up a new account roughly 5 weeks ago. The previous pool guy could not keep the pool clear so home owner called me up to get a second opinion. I tested as follows:
FC:0
CYA:0
PH:8+
TA: 150
CH: not tested
I thought “no wonder he is having a tough time, there’s no CYA in the pool” and 95 degree heat week after week plus rain will crush this pool.

I took the job expecting an easy fix. Added 2 gal of Leslie’s instant conditioner, shocked the pool, and cleaned cartridge filters (24psi and overdue for cleaning). After a week the pool was crystal clear so I handed it over to my employee for weekly cleaning every Thursday. Pool went green two weeks in a row by Tuesday so I checked his job notes which stated 0 CYA every visit since then so I instructed him to start using Leslie’s Chlorbrite (dichlor) to shock the pool. This was last Thursday and this Thursday. Today is Friday, one day after he used the chlorbrite, so I made a visit to check on the pool to find CYA still at 0ppm.

What could be preventing this pool from holding CYA? Astonishingly, the pool held chlorine over night last so I’m completely stumped. TIA
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,982
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
How are you testing?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,982
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If the pool holds chlorine there is not an ammonia/ bacteria problem. So if you added enough stabilizer to get to xx ppm, and it is not there, the product used was faulty.
 

Southern Swimming

In The Industry
Oct 21, 2020
11
If the pool holds chlorine there is not an ammonia/ bacteria problem. So if you added enough stabilizer to get to xx ppm, and it is not there, the product used was faulty.
Is there any additional reading I could do on CYA? I feel like I’m missing something chemically.

I had a tech add 2 more gal of instant conditioner which should add 30ppm CYA. If tomorrow’s test comes up negative, I’d like to dig a bit deeper. Do you have any additional info on the bacteria issue? I’ve read that it is a rare instance and requires water to be anaerobic (stagnant) and requires certain other parameters that I can’t remember.