HVAC-NW

I've had very good luck using a HortiCare PH Check pen. Been using this same ph pen for several years and they remain very accurate and reliable with only an occasional calibration. I get consistent accuracy to within .1 scale when comparing to the Taylor K-2006. On the other hand I've had bad luck with the Oakton (Fisher Scientific) eco testr/ph 2 pens. Several of them failed for no apparent reason, even with proper care and storage solution used. After 3, I gave up on them. Haven't had even one of the HortiCare's fail going on three years now. https://www.amazon.com/HORTI-HortiCare-pH-Tester-716020/dp/B00AE169SW

The Deuce replacement also calls for a significant increase in calcium hardness from the Ace's recommended 50 to between 200 to 400 ppm with the Deuce. If this is not followed, the warranty is voided.

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.

I agree that having your own K-2006 test kit would be a wise investment and ensure accurate results. Taylor also recommends on page nine of their Pool & Spa Water Chemistry booklet that one should test the water sample immediately after obtaining the sample. They state "If a sample sits for as little as one minute after removal, values may change-- especially when testing sanitizer levels".