Calibrating a Hayward T-15 SWCG

fatherfigure

New member
Apr 27, 2023
4
Chandler, AZ
Hello. First post here. I think I've got a handle on my situation but wanted to gather any additional feedback from this pool (no pun intended) of experienced users.

I've got a ~35K gallon SW pool. Current salinity is around 3Kppm. New T-15 in place.

I use the Taylor K2005 to keep my chemicals balanced throughout the week.

My ranges are typically right around:

pH: 7.4-7.6
Total alkalinity: 90-110
Calcium hardness: 480
CYA: 50

My question is concerning the chlorinator. I disabled my chlorinator for a few days and allowed all the free chlorine to dissipate through UV exposure (hot long sunny days in AZ). That seemed to work just fine. FC dropped like a weight from 6ppm to near 0 in 2 days. Now I'm working on establishing a healthy % based chlorinator setting. I set it to 35% overnight and woke up to test the water and it was at 5ppm, left it to run for a full additional day and it jumped to 10ppm. Turned it off, and it seems to drop anywhere from 4-5ppm every day it isn't running from pure UV exposure.

Based on this data, I have concluded (barring unmentioned external factors) that a natural UV burn rate of FC 4-5ppm per day exists, and that is while the cell is running at 35%. So without the cell running, I lose 4-5ppm per day, but with it running at 35% it rises 4-5ppm per day (while simultaneously experiencing UV burn).

So if I am understanding what's happening, 35% chlorinator setting is really generating more like 10ppm per day, which is being reduced to 5ppm per day after UV burn.

In order to maintain a consistently safe and ideal level of FC, what rate and percentage should I be setting my chlorinator at, and should I only be generating chlorine during the day or at night or both?

Also, for whatever reason, it appears with Hayward you can set the chlorinator on a schedule, but it doesn't actually function. You have to manually turn it on or off which kind of defeats the purpose of having a schedule option, and makes it difficult to automate chlorine generation.

Sorry in advance for the convoluted breakdown of data. I tried to make it as straightforward as possible based on what I have collected.
 
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Welcome to the forum!

Per spec, the T-15 cell will add 1.45 lbs/day of CL when set at 100% and running for 24 hrs. At most this would be a FC rise of 5 ppm per day in a 35k pool. At 35% it should only be about 1.75 ppm so something is not adding up.

Are you sure you have a 35k Pool?

Do you have only one T-15 cell?

How old are the reagents in your test kit?

Also, please fill out your signature:

 
Thanks, Mark.

Pool gallons are estimated since I've never done fill, going by diameter and depth.

Only one T-15, and it's brand new and tested.

Reagents are brand new and results are closely in line with Leslie's water test. I know they aren't looked on kindly here for various reasons, but that's really all I have to go by for comparison at the moment.

Thank you!
 
Ascertaining the volume of water in the pool is going to be a problem. It has variable depth as several places and an amorphous edge design, not ovular, circular, rectangular or square. It is free form. Builder made. I am attempting to get the exact design specs from the builder, but they transferred everything to another company after going out of business, so I'm working with my HOA on finding that.
 
My suggestion is to set the swg at 10% and let it run for a few days and see where it stabilizes. Adjust from there to get to 10% of CYA OR 5 PPM FC.

Turning off the SWG to measure UV extinction is not accuract as low FC levels will encourage bacteria and algae consuming CL.

FC levels should never dip lower than 5% of cya levels.
 
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