Switched to SWG, Couple questions.


May 8, 2017
Columbus, GA
I've been a lurker for a while and understand the basic of water chemistry. I'm not expert by any means, but I get the big points. I have a FAS/DPD, of course; Taylor 2006, so all my test results are from that*. I just finished SLAMing my pool for open, and everything blued up and looking great. I just installed a Hayward AquaTrol, though I'm not generating right now as I'm waiting for FC levels to come down. Unfortunately I ran out of 0871 on my last day of SLAM, so my chlorine numbers are off of strips until more reagent comes in. I also have a little hot-tub, that I have been running an drop in SWG for about 3 years, again water looks great.

Pool (7600gal):
FC: 10+ (Strips)
PH: 7.5
TA: 125
CH: 200
CYA: 50
Temp: 68
CSI: -.036

Spa (175gal):
FC: 2 (Strips)
PH: 8+ (6 Drops on the demand test)
TA: 125
CH: 250
CYA: 60
Temp: 100

I know my TA a little high on both, with kids splashing and just general use the pool will come down on it's own and for the hottub fixing the PH may bring that down some. Alright, where I need some help and advice. This is the first year I've cared about CYA in my hottub/pool. Before now I was using TriChlor in pool (Frog, I know boo-hiss!), and the CYA build up over the year was why I switched in the first place. I hadn't added any CYA to the hottub until now, because I had thought with it being a covered hottub, I didn't have to worry about losing chlorine to the sun. Lately I have been reading the CYA helps longevity of the SWG cells, and the Hayward manual says it's needed between 60-80, and TFP charts say 70-80. (Okay, okay, I get it! =P ) Using the CSI math and poolcalc, I'm trying to keep my CSI between .2 & -.2, per my Hayward manual -- largely using CH to give me some wiggle room.

Am I on the right path with CYA/CSI, that's something that's completely new to me. Second question, calculating how much Acid to put in for 6 drops on a 175gal tub. None of the charts go down that low. Also, I do plan adding Borates to get that silky smooth and PH stabilization I've been reading about.

Anything I'm missing or that might apply to my tub/pool?


Bronze Supporter
Dec 22, 2016
Arlington, Texas
Use the taylor book. Acid additions are linear. 6 drops for 1000 gallons is 5.5 fl oz. So 5.5/1000*175=.9625 fl oz. I would hold off on borates. Actively get your TA down to 60-80(probably closer to 60) and see how your pH mellows out.

Also, CYA in the hot tub reduces harshness of the FC, so it is a very good thing to have.


May 8, 2017
Columbus, GA
How much does CSI matter to the SWG Cells, Pool, and Hottub? Lowering TA to 60, drops the CSI to -.4, lower than Hayward recommendations. To stay around -.2, it's 60/400 or 70/300 (TA/CH). Oh and I now my Spa's FC is low. I have the SWG in boost (extended cycle) catching up for the CYA addition.


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

SWCG pools tend to stay at 7.8 for pH...

Just letting your pH go up to 7.8 and leaving everything else alone, your CSI drops to -.01 which is perfect...

What I know about Spa's would fit into the period at the end of this sentence.


Jim R.


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
Aug 10, 2012
FL panhandle
Keeping CSI negative will help prevent scale in the pool and the SWG cell. -0.3 to 0 is best. But, -0.4 is ok too. +1 to Jim on letting pH stay 7.8, don't lower it until it rises to 8.0.