what about cyanuric acid?

[txwillie]

Do I need it? Just switched from bromine to dichlor last weekend. After the daily soak and dichlor dose, the free CL reads in the 5 ppm range, next morning, ZERO. Shocked the heck out of it using dichlor last night, over 10 ppm. Just checked and it is down to around 4 ppm, so I think that looks right, but do I need cyanuric acid (stabilizer)? Back when I had in ground pools, the shock and tabs both contained cyanuric acid, but the dichlor I use with the spa does not.

thanks,

txwillie

[HotTubMan]

Do you need it, no?

If you want to use dichlor or granular bromine, you've got it anyway. It is used in the process of making dichlor. Most bromine powders use dichlor in there manufacturing.

[Spatech_tuo]

Do I need it?

IMO, one of the best things about using dichlor in a spa is that it does as you stated. Add it after you get out and you'll drive up the chlorine level but the next day you go in the residual is low and when you get out you simply hit it again and repeat the cycle. Do you really want to go into the spa with a high chlroine level? With Bromine you get a constant sanitizer level which works well but smells like chemical soup IMO. the dichlor method is what I prefer as you spike the level when you get out, go in to a reasonably low level of chlorine and spike it again when you get out.

[txwillie]

I get ya spatech tuo, just a bit surprised to see the cl level at zero 6-8 hours after dosing. may not have been dosing quite enough, still getting the feel for the new routine. I can say for sure that the chemical odor with dichlor is much less than bromine. Water still has that new water sparkle. after  a week or so on bromine it loses that quality. I want to see how it compares at 1 month, 2, etc.

txwillie

[tony]

Dichlor contains cyanuric acid also....almost 50% by volume.  Dichlor can also be used in a pool, but it's high cost makes it prohibitive.  CYA protects chlorine from sunlight.  If you sanitize a pool with trichlor or dichlor, you constantly add CYA.  If you use an alternative chlorine such as cal hypo or liquid chlorine, you should add CYA separately.  This only applies to outdoor pools.  Indoor pools should not use anything that contains CYA as it does not break down.  The only way to diminish is to dilute.

Dichlor is great for spas because of its quick dissolving characteristics and its neutral pH.  CYA is not a concern because (a) the spa is covered most of the time and (b) water is changed often enough that CYA overdose does not really apply.  If you have a Taylor test kit, you can keep tabs on your CYA level.

[Steve]

Very good post Tony!

Steve

[tony]

Thank you, Steve.