Don't Use Liquid Bleach Warning?

[sbluhm]

Hi,

The owners manul for our new hot tub clearly states in several places "DON'T use household/liquid bleach", and DO use a granular form of sanitizer.

As a happy BBB user for my pool, I'd like to use bleach with the hot tub as well.

Is this warning just the manufacturer trying to protect themselves from some sort of liability, or is there a valid reason?

If I'm correct, if I always use granular chlorine, which is stabilized, the CYA level will continue to rise. I guess it's not too much of an issue since you drain/refill every 4 months anyways?

Thanks!

 

[sandybeach]

We just use our pool water to fill our hot tub , works great, its already balanced

 

[PaulR]

After a refill, I use dichlor for a while until the CYA is in the 20-30 range, then I use (gasp!) bleach. Chlorine is chlorine, no good reason for them to say don't use bleach.

Of course, because I have 12.5%, it's ridiculously small quantities, 15-20ml every couple of days seems to keep my FC in range. I've also seen a claim that this method lets you go much longer between refills although I don't know quite what all goes into that decision.
--paulr

 

[frustratedpoolmom]

Perhaps the hot tub manufacturer also sells spa chemicals. :?:

 

[chem geek]

The reason the tub manufacturers say not to use bleach is that they believe that most people cannot understand the concept of using more than one type of chlorine and if one used ONLY bleach, then the active chlorine level in the tub would be too high and would degrade hot tub covers and possibly other components way too quickly (and would also oxidize swimsuits, skin and hair more quickly). Commercial/public spas typically use chlorine without Cyanuric Acid (CYA) in the water and are harsh because of this, but they are typically designed to handle this.

So the manufacturers take the simplistic approach to just use Dichlor. However, as the CYA level builds up from Dichlor use, the chlorine effeciveness drops. This can potentially lead to hot tub itch bacteria growing after a month or two (still speculative, but there is a small trend for this). Remember that for every 10 ppm Free Chlorine (FC) added by Dichlor, it also increases Cyanuric Acid (CYA) by 9 ppm.

The best approach is a hybrid one of initially using Dichlor for about a week, or whatever amount leads to around 20-30 ppm CYA, and then switch to bleach. That way, you have a consistent chlorine level that is not too harsh on the hot tub cover but is still strong enough to kill bacteria quickly. Note however that you must manage your Total Alkalinity (TA) and keep it low or else the pH will rise and that can lead to scaling. That's another reason the manufacturers say not to use bleach -- if you do and don't keep a lower TA (50-80 ppm), then the rising pH can lead to scale and damage your tub. Again, they figure most people can't comprehend this requirement to keep the TA low and to watch the pH and adjust accordingly.

Richard

 

[sbluhm]

Ah, thanks for all the good information. I should have known not to doubt the bleach!

I thought about filling the hottub with the pool water.. My only concern with that is the fact that I've added salt to the pool, even though it doesn't have an SWCG. I know the ppm of the salt is very low, should the potential corrosiveness of the salt even be a concern? I mean, it's running through the pool pump, and maybe the chlorine is a lot more corrosive anyways? The TA in the pool will be higher than 50-80, but I could always adjust it down.

I have a good test kit and am prepared to break out thepoolcalculator.com at a moments notice...

Do a lot of others fill their hottub from the pool?

 

[launboy]

My plan is to run a stand-alone hot tub on pool water. Course the way I'm doing it is a little different because they are plumbed together and can switch water with the turn of a valve. I do plan to use the original spa pack as part of this set-up and the pool water is saltwater(though no SWCG yet).

HTH,
Adam