Chlorine is always low in hot tub

[brother1]

Hi there,

Ive had my hot tub for just over 3 months and have always struggled to keep the chlorine level within range.
I always make sure my TA and PH levels are ok before adding the chlorine.
I've just done my first water change and spent ages getting the TA and PH levels spot on but whenever we go to use the tub the chlorine level is nil.
Is it the case that i need to do the chlorine every day, even if nobody is going to use the tub?
Any advice would be greatly appreciated as this is driving me nuts

 

[ajw22]

TA and PH have no effect on CL level. They are independent.

Is your hot tub outdoors? Is the water uncovered and exposed to sunlight?

 

[jseyfert3]

You can often get away with every other day, if you haven't used the tub recently so there aren't any organic materials eating up the chlorine.

My experience was that even with chlorine good before getting in, and dosing on getting out, and showing before entering, the next day the chlorine would be almost nil again due to organics (sweat, etc) left from being in the tub. After that, usually adding every other day was sufficient to keep the levels within proper TFP levels. Note that I always added enough to bring the level up to the high end of the PPM range, which is 6 PPM for 30 PPM of CYA..

Going every other day I could squeak by without it dropping below the 2 PPM minimum.

Every day is best, though. If you start noticing trends, such as steady chlorine loss of X ppm per day when not being used, you can start adding the proper amount of chlorine every day without testing every day. You can test every two or three days, or what works for you, as long as you are sure you aren't running out of chlorine in the tub.

 

[jza1736]

What TA are you shooting for? Manufacture spec of my tub is 80. But that was impossible to get with the PH balanced. My spa likes TA 50. PH stays in range.

The chlorine, like others have said, is not dependent on PH or TA.

My spa is bromine which is also A PITA. it has a floater. 4 gets to high and 3 is too low. I'm playing with it all the time. I might switch to salt as my pool is truly A TFP!

 

[ant 83]

Well, first, we should probably confirm that you have the recommended testing equipment. You're not using paper dip strips, are you?

Second, have you used a pipe cleaner to clean out the scum in your pipes? TFP recommends ah-some. Pipe scum is an ongoing issue with spas, and definitely increases chlorine demand.

Third, are you being diligent about cleaning out your filter? Ive found that just replacing my filter with a new one can improve things a great deal.

Fourth, you'll want to check your bleach for strength. Test FC, add bleach, then mix for a few minutes, and test FC again. You very well may not be adding as much chlorine as you think.

Fifth, are you testing for CYA numbers? Ive found that low CYA means chlorine disappears faster. Trying to compensate with more chlorine makes CYA drop faster. This effect will snowball into a zero CYA situation if you don't test for CYA.

Sixth, dropping spa temps has very noticeable effect on chlorine demand. Even just 3 degrees is worth doing in my experience. 5-10 degrees is VERY noticeable in lowered chlorine demand.

Seventh, I hesitate to even mention this, because it's NOT a TFP method, and is likely prohibited by your spa warranty, but I have had much better water quality since I started doing it. That is using small chunks of trichlor in a floater that has been dialed back for slow dissolve rate as my source of acid to lower PH. I only add the trichlor in small amounts when PH is higher than 7.6. I use this floater: Amazon.com : Ocean Blue Water Products Floating Chlorine/Bromine Dispenser : Garden Outdoor
The trichlor takes a few days to dissolve, and adds back chlorine, prevents PH from rising, and prevents CYA from falling.

These are all the suggestions I can think of.