Hotsprings Ace System Requires Strange Parameters

[Skyscraper]

Hi All,

I have followed Nitro's advise on hot tub chemistry over several years with great success. I recently purchased a Hotsprings tub with the ACE salt water sanitizing system. It calls for the following parameters:

Salt - 1750 ppm

Hardness - 50 ppm

Alkalinity - 80 ppm

pH - 7.4

Chlorine - 3 ppm

When I plug these numbers into the Pool Calculator, it gives me a Calcite Saturation Index of -.86, which is way lower than Nitro's suggested 0-ish.

Does anyone know, if I dial my water in to these levels, what the possible negative affects will be?

Thanks in advance

[HVAC-NW]

I also recently purchased an Hot Spring Spa (Prodigy @ 290 Gal) with Ace system and wondered the same things as you.  I've had it since July 1st.  What I ended up doing is using the Taylor Watergram that comes with the K-2006 water test kit.  Right now I have the following parameters:

CH = 50

TA = 120

PH = 7.9

FC = 3 to 5

Keep in mind if you're going to supplement with bleach, this will slowly raise the salinity of your tub.  I found this out after increasing my TA with baking soda and supplementing with bleach when the Ace system couldn't keep up after heavy usage.  It ended up pushing my salinity levels up to the point the Ace system tripped off line from too high of salt levels.  I drained 3/4 of the spa water and refilled with fresh tap water.  This lowered my Ace reading to about 1/4 of it's scale.  This also accomplished lowing my CYA back down to the recommended level of 20 to 30.  I was supplementing my sanitizer with Dichlor instead of bleach, which ended up increasing my CYA to above 100. That was before I learned by reading all the great info from this forum. 

Using the first three parameters with the Watergram gives me a balanced spa @ nearly a 0 saturation index.  To get close to balanced (for your present conditions), you would have to raise your PH to around 8 or better, so I would increase your total alkalinity in the area of 100 - 120.  Right now your parameters indicate an acidic condition so I'd make some small changes adjusting the TA and PH upward.  

 

[chem geek]

You only need the CH higher in a spa if you have a plaster surface or to reduce foaming, but the ACE system requires low CH levels usually 50 ppm or lower and they have a calcium remover pouch to lower the CH.  So for ACE you should not try raising the CH.  If your spa is not plaster (most are acrylic instead) then you don't need to worry about the low CH.