Using a lot of Muriatic acid each week with a SWCG. Let's do real maths here.

Justworkhere

Gold Supporter
Mar 11, 2020
6
Fort Worth, TX
I go through about a gallon a week. It's a plaster pool that is still relatively new. I usually go to the pool store and get a box of 4 gallons and don't let them sell me anything else. I'm good for about a month. When I test my water and it's above 8, I add about 1/2 a gallon and test the next day. It's usually down in the 7.6 range and by the time I test again in a few days it's back up around 8 so I add another 1/2 gallon. Sometimes, I feel like I am the only person on the forum who isn't using measuring cups.

This....

I am a relatively new pool owner. I have a Saltwater Generator that has been off through my relatively short time of ownership (6 mo) due to it being winter time. I have a 12,000 gallon pool that needs about a half gallon a week of muriatic acid as well. I don't use measuring cups either. It's pretty much always a half gallon that does the trick, unless there was a significant amount of rain that week. It was replastered about 4 years ago. I keep the TA around 100. The Ph fluctuates the same as above. I go from 8.0 down to 7.4 back up to 8.0 every week. Is 1/2 gallon a week too much to add for this size pool? I feel like I am missing something else.
I'm also adding about 5 lbs of baking soda every other week to keep the TA at 100 to counteract all of the muriatic acid I am adding.

I'm adding bleach for chlorine while the SWG is off and try to keep it around 3-4.

Is there anything I could be missing or is this just normal for some pools? I live in Fort Worth.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
19,403
Bedford, TX
jwh,

I find that with a SWCG pool, a pH of 7.8 is just about right. Dropping down to 7.2 or 7.4 just means using more acid...

I would not do anything about TA unless it drops below 50..

I have three saltwater pools in the DFW area and use a total of about a gallon a month.

Thanks,

Jim R
 

JamesW

TFP Expert
Mar 2, 2011
21,075
I'm also adding about 5 lbs of baking soda every other week to keep the TA at 100 to counteract all of the muriatic acid I am adding.
This is the main problem. If you keep the pH at 7.8 to 7.9, the CYA at about 60 and the CSI between -0.3 and 0.0, you can probably get the acid demand to about 1 gallon per year.

If you need to lower the pH, don't go below 7.9.

I would allow the TA to go to 50 if necessary. Even below 50 is ok as long as the CSI is good.

If you need to raise the TA, don't go above 50 or 60.

People tend to believe that the pH will begin to "bounce" around if the TA is low, but this is not accurate.

The pH will not move very much unless something acidic or basic is added.

pH doesn't just begin to fluctuate wildly for no reason.
 
Last edited:

Justworkhere

Gold Supporter
Mar 11, 2020
6
Fort Worth, TX
This is the main problem. If you keep the pH at 7.8 to 7.9, the CYA at about 60 and the CSI between -0.3 and 0.0, you can probably get the acid demand to about 1 gallon per year.
Thanks, so at 7.8 or 7.9 I don't have to worry about scale building up as well as the chlorine not being as effective?

The pH will not move very much unless something acidic or basic is added.
When I turn the SWG on it will start going basic, correct?
 

JamesW

TFP Expert
Mar 2, 2011
21,075
Scale depends on the CSI, not the pH.

Chlorine will be plenty effective as long as you maintain the correct fc/cya ratio of at least 7.5%.

SWGs are pH neutral when the amount of chlorine being generated is in equilibrium with the amount of chlorine being lost.
 

Rattus Suffocatus

Silver Supporter
Jun 5, 2019
1,236
Corona de Tucson, AZ
Interesting. So in another thread I was told I should get my TA down to 80 and drop the pH to the 7.5-7.6 pH range if I add a SWCG-- implied even before I do it. I am *thinking* about it (but I think I'm going to wait until the panic is over with in case I have to sell the house instead) but I have been very stable at 7.8 and 120 TA, CH 225. CSI around 0. Is that okay for a cell? Or is it not okay?

I suspect since I am in AZ that the CH will creep up over time so I probably will have to eventually drop the numbers downwards eventually, but if I keep CSI near 0, I am good, right? Or am I missing something special with the SWCG's?
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
13,760
Pleasanton, CA
The PH inside a SWG near the plates is going to be higher than the pool water so there would still be some potential for scaling even with a CSI of 0, as measured from the general pool water. I find my cell can still scale even with a negative CSI but I also have much higher CH levels than you.
 
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Rattus Suffocatus

Silver Supporter
Jun 5, 2019
1,236
Corona de Tucson, AZ
Thanks. It's a fairly well know fact that in Tucson (and in Phoenix I suppose) the CH levels will creep up quickly over time, and even to ridiculous levels as some others have had happen. (My detached water system luckily is a little better than the main Tucson system.) But hopefully if and when I add a cell I don't need to go to extremes to bring the balance point down to a lower pH before I can even run the cell at all. To do this in a hurry with high TA requires aeration and that turned out to be an inexact science and a bigger pain than one would think on the detached hot tub the two times I've done it so far.... I would prefer to creep it down over time....