keep cya in salt pool low???

[ssmith1092]

hello everyone.

so i been doing some thinking and not sure if im right or not. i know in a salt pool cya should be 50 to 70 ppm, so the sun doesnt eat up all the FC. but with cya being that, you lose chlorine strength. so lately i have just not been adding cya and just keeping my FC high. so far i been keep the generator on 45% and even on the most sunny hot day, by FC doesnt go under 6ppm. i also keep ph low, 7.2-7.6 and i keep salt around 3200-3500. is this a cost effectice way about going without cya.

 

[tim5055]

No, the most cost effective way i sto keep the CYA higher. The chlorine does not loose strength, it is just bound ot the CYA and is available to be released for sanitation.

Stick with the Salt section of the [FC/CYA][/FC/CYA]

 

[JoyfulNoise]

How many hours per day is your pump/SWG running?

 

[ssmith1092]

pump is running 12 hours a day.

 

[JoyfulNoise]

So right now your pool loses about 1.4ppm FC per day (based on your pump run times). As the CYA gets lower, you'll see more loss which will mean your FC level will drop OR you'll have to run your pump longer to achieve the same FC. You live in Delaware which is not a particularly hot climate or high in UV exposure so I would not expect you to need very high levels of CYA. That said, keeping your CYA up at the higher recommended TFP levels could potentially save you a few hours of pump run time.

As a comparison, I live in a much hotter and dryer climate than you and my FC loss is only, at most, 1ppm/day. My SWG runs at 40% and my pump runs at higher speed less than 6 hours per day. My CYA is kept at 90ppm.

 

[ssmith1092]

how was you able to calculate FC lost?

but my fc lost is probably less then that. my pool gets alot of shade. its now 10am and only about 1/3 of the poik has sun right now. and about 3 hours before sunset, my pool is completely shaded. heating my pool will be nextbsummer project.

 

[JoyfulNoise]

You have a T-15 Hayward cell and it produces 1.25lbs of chlorine gas per 24 hours of run time. So, for the cell running at 45% for 12 hours, you get -

1.25 x (12/24) x 0.45 = 0.28125 lbs of chlorine gas

Assuming it all dissolves into your pool, the ppm's of FC added are -

0.28125 / (25000 x 8.34) = 1.35ppm

So, if you measure your FC and you see no change in FC day-to-day, then the amount of chlorine added to your pool by the SWG is offsetting the amount of chlorine lost each day.

With the shading you report, then I would expect your FC loss rate to be quite low as sunlight is the biggest source of daily FC loss. You can probably just maintain 60-70ppm CYA and that would be more than enough to protect the chlorine generated by the SWG. My pool, by contrast, gets full sun from early in the morning until sunset and so it needs higher levels of CYA to achieve lower total FC loss. If my CYA goes below 70ppm, I see a very noticeable increase in FC loss.

 

[ssmith1092]

ok cool.

now even with my current cya being under 30ppm. i like to keep fc high as a algae provention. what should my fc be say if i raise to 60. i know accorsing to the cya/fc chart. but i like to be extra safe

 

[JoyfulNoise]

ok cool.

now even with my current cya being under 30ppm. i like to keep fc high as a algae provention. what should my fc be say if i raise to 60. i know accorsing to the cya/fc chart. but i like to be extra safe

You really don't want to operate that way. The standard FC/CYA ratio for an SWG pool is 5%. So, at 60ppm CYA your minimum value is 3ppm FC. If you maintain a target of 4-5ppm, you will be fine.

When you add chlorine in excess of the standard FC/CYA ratio, you are simply wasting chlorine as it degrades faster at higher concentrations. In your case, you're running pump much longer than really have to and thereby wasting money on utility electric bills. If you were manually chlorinating, you'd be wasting money on excess bleach.

Just stick to the TFP recommended levels and your pool will be fine.

 

[jblizzle]

Shouldn't the T15 be producing 1.4 or 1.45 lb of chlorine? I thought it was the T9 that produced 1.25 pounds.

 

[JoyfulNoise]

Hmmmm...JamesW can tell us. I always thought the T-15 produced less chlorine than the Pentair IC-40....but maybe Hayward has increased it....

- - - Updated - - -

If it were 1.4lbs/day then it would be 1.5ppm/day FC loss.....still on the low side.

 

[Swampwoman]

I think its 1.45 lbs, as I recall. At least, that's what I've used for my calcs and it does what I predict