SWG Pool Chemistry Targets

Oct 2, 2016
20
Tampa/FL
#1
1st post... :p

I am narrowing the chemistry targets based on all that I have learned thus far and just have a few questions. Please refer to my signature for the pool specifics. The pool is not heavily used (weekends with the family mostly).

I have been doing the pool chemistry adjustments since the first couple of weeks after startup and for the most part, it's been quite easy. Basically, it seems the pH increases steadily and I just have to add muriatic to keep it in range (about 1/2-3/4 gallon a week). I also occasionally add CYA. I was told that the acid is steadily needed because the pool finish is curing, but I am starting to wonder about that.

Typical Pool Values
FC=4
PH=7.6-8.2
TA=50-60
CH=200-300
CYA=40-80
Salt=2300-2500

Variances in Published Targets
Parameter/ Pool Finish&SWG Manual/ TFP Pool School
FC/2-3/4-6
TA/80-100/60-80
CH/200-400/350-450
CYA/30-50/70-80

Questions:
1. pH - Do you see any reason why I have to continually and steadily add acid each week?
2. FC - Are there any known issues associated with keeping the FC elevated above these targets? I am sure my equipment/finish is not unique.
3. TA - Same question as 2 for TA? Also, I tend to sit on the low end (50-60ppm) of the target and do not adjust it. Do you feel this is a concern? why?
4. CH - What is the basis for the higher calcium for plaster pools? If my pool finish info says to keep it at a lower value, should this override? I tend to sit at the lower end of the range. What is the concern about staying below the suggested range?
5. CYA - What is the concern with keeping the CYA at 30-60 or basis for keeping it at 70-80? Any known issues with the finish or equipment operating at the lower range?

Thanks again. Just trying to understand the differences to make final decisions about the targets.
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
41,197
Tucson, AZ
#2
Welcome to TFP!

1. New plaster will drive up the pH as it cures. A SWG will also drive up the pH as it generates. Although there are ways to slow it.

2. I am not sure what ranges you are referring to, but recommend you check out Pool School for the levels we suggest to avoid problems. The required FC level is a function of your CYA level.

3. Lower TA like you have can help slow the pH rise, especially with a SWG running.

4. If your CSI stays too low, the water can leach CH out of the plaster. My CH is currently way below recommendations, but by keeping the pH higher, the CSI is not too low.

5. The CYA has no impact on the finish. The higher CYA for SWG pools allows the SWG to not work as hard and thus the cell should last longer.
 

Naplespool

Well-known member
Mar 26, 2017
78
Naples/FL
#3
Hi and welcome, the advisors/members here are terrific.

I'm in Naples and just fired up a 17,250 g, plaster, SWG pool in December. I'm using 2-3 quarts of MA per week. I've reached the conclusion that it is the SWG causing most of the PH rise. I've slowed it down some by:

1) bringing the cya to 80 (cya shouldn't vary quickly) so that the swg can be set to run less. I'm now at 35% for 12 hours which is 17.5% of the day. I've chosen to run 12 hrs to add chlorine during the daylight hrs. when it is mostly consumed.

2) keeping TA between 70-80 ppm.

3) not running bubblers and spa more than needed. Do you have a spillover?

4) I also added Boric Acid but later was advised it is better to wait until you know your pool.

Here are my targets:

FC: 9 at cya=80 per Chem Geek's revised CYA/Chlorine chart
CC: 0 - <0.5 ppm
CYA: 70-80
PH: 7.6-8.0
TA: 60-80
CH: 350-450
Salt: 3400-3700
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
10,494
Bedford, TX
#4
pg,

Welcome to TFP... A Great resource for all your increasing pH questions.. :shark:

Your pH is continually increasing due to your new plaster, your SWCG, and your spillover or other water features.

You can't do anything about the plaster but wait. But as time goes by the effect that new plaster has will continue to decrease.

The less you can run your SWCG the less pH increase there will be. A CYA of 70 or 80 will allow you to dial the SWCG's output back.

The less you run your spillover and other water features, the less it will cause your pH to increase.

In your question #3, you say you don't adjust your TA, but oh yes you do... Adding MA reduces both TA and pH. I believe the reason your TA is so low is because of all the acid you are using.

Most SWCG pools like there pH at 7.8. My pool will stay at 7.8 for several weeks at a time, it will stay at 7.5 for about 30 seconds.. :cool:

Some questions for you...

1. What is your percent of output on your SWCG?
2. How long do you run your pump each day?
3. Other than the spillover, do you have other water features?
4. How many hours per day does your spillover or water features run?
5. What test kit are you using to get to your numbers?

Thanks for posting,

Jim R.
 
Oct 2, 2016
20
Tampa/FL
#5
Thanks to everyone that replied.

1. SWCG@40%
2. Need to verify but I think the pump runs 10 hours per day. 9am-7pm
3,4. I have a spillover that is usu running with the pump. I usually keep the bubbler off.
5. I got a basic kit with the pool. OTO chlorine is always vivid yellow which I think is always at least 4ppm FC. I also take samples to Leslie's and they usually agree with my basic tests but I have thus far relied on their FC readings vs mine. But, I ordered a Taylor 2006-salt this weekend, so I can dial in the Chlorinator better.

I just kicked up CYA to 70-80. This requires me to kick up FC to 8-9 right? But you mentioned I should be able to reduce the SWG setting. Does higher CYA need more chlorine from the SWG or less to get a sl higher FC level? What about to get the same FC level?

Also, sounds like I should increase TA a bit with baking soda. Will that increase or decrease PH stability? I think I got conflicting answers on that.

Also, is anyone familiar with the pool finish life expectancy factors able to answer what the effect of higher CYA and FC is on the life of the finish? Higher when comparing TFP targets to the pool finish vendor recommendations (see 1st post).

Thanks again.
 
Last edited:

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
10,494
Bedford, TX
#6
Pg,

Check out this chart... https://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock

Notice there is a SWG section... With a CYA of 80 your target FC should be 6, with the very minimum at 4 ppm. My thought is that it will be easier for the SWCG to maintain 5 or 6 ppm with a CYA of 80 than 4 ppm with a CYA of 40.

If you can, shut the continual spillover off. If you have automation, you can schedule it to come on for an hour a day to keep your spa chlorinated. If no automation, then you might try reducing the amount of spillover to a trickle.

The CYA/FC levels recommended by TFP will not harm your plaster

Thanks,

Jim R.
 
Oct 2, 2016
20
Tampa/FL
#7
In Naplespool's post above, I was studying the chemgeek chart to undestand how he got a FC target of 9 with CYA=80. That value is for a manually chlorinated pool. For SWG, the FC should be 6.

See note 3 in Chem geeks chart. It hints at the difference and the green text and link at the top to the simplified chart agrees.

Chlorine/CYA Chart
 
Last edited:

Naplespool

Well-known member
Mar 26, 2017
78
Naples/FL
#8
Yes, you are correct. In the fine print below his chart chem geek says 4.5% of cya for FC min. That means a minimum of around 4 ppm and a target of 6. Thanks both of you for the clarification.