PB says with SWG you are just trading muriatic acid for chlorine

Foosman

Bronze Supporter
Jul 21, 2016
361
Austin, TX
I asked a coworker about his SWG and he says he adds muriatic acid to his pool at least twice a week. A pool builder said the salt changes the PH level and says there is no point to a SWG as it eliminates the need to add chlorine, but now you have to add muriatic acid. Can someone comment, as I'm trying to decide on SWG for a new pool.
 

JamesW

TFP Expert
Mar 2, 2011
21,549
SWGs are ph neutral. Any ph rise comes from a TA that is too high.

Once you get your TA right, you should almost never have to add acid. What's your fill water TA?
 

fkrobertson

Bronze Supporter
May 23, 2016
11
Phoenix, AZ
I switched and we do use more acid. That is mainly due to our fill water having high TA and large amounts of evaporation in the hot Arizona summer. When I say "more" I mean about a 1/2 gallon of 31.45% MA a week. Keep in mind our fill water TA is 130, I have a 20K gal pool, the pool is in full sun, and the temperature is regularly above 105. If you don't have high TA or have a lower evaporation rate than I do, it will be easier to dial in your TA and you won't be battling ph. I've seen many post on here where SWG owners add acid very rarely.

Even if your fill water TA is a little high, consider that muriatic acid can be purchased at high concentrations and has a long shelf life. Liquid Chlorine is less concentrated and does expire. If you're worried about lugging gallons of MA instead of Chlorine, I'd guess you'll be lugging less MA with a SWG than you would be lugging gallons of Chlorine without one. These are just my anecdotal numbers, but I need to add about 64oz of MA to drop my pool from 8.0 to 7.5. I do that about once a week. So 2 gallons of MA lasts a month. Contrast that with the 1.5-2 ppm FC loss I experience daily. I need 32 oz of 12.5% Liquid Chlorine or 64 oz of household bleach a day to meet my chlorine needs. That works out to 7.5 gallons of 12.5% or 15 gallons of house hold bleach every month. I can make one trip to the local hardware store and get a month's supply of MA relatively easily. Before I had a SWG, I did weekly bleach runs.

Others may disagree with only adjusting pH weekly. People more knowledgeable than me will chime in. I've found that I can add acid and let the pH drift up over a week or so without negative consequence. On the contrary missing a chlorine addition for even a day or two can get you into trouble fast. For my money, the SWG is probably a little more expensive than manually adding chlorine, but it is a lot more convenient and forgiving.
 

grottoguy

LifeTime Supporter
Aug 24, 2014
462
NJ
I add about a gallon every nine days when I do not run my waterfall or other aeration ( which would make me add it more often). My TA is only 60 and I don't think I should lower it any more than that. From my experience I think your PB is right, but others do add very little acid. You may want to consider a Stennar pump that will add chlorine automatically ( you just fill it up every month or so) and you can add salt to the pool if you like the feel of it.
 
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lightingguy

LifeTime Supporter
Jun 17, 2010
513
Glendale, CA
Salt changing the PH level is silly.

As mentioned the source of PH rise in pools is TA - which is compounded by the SWG. The SWG causes CO2 to out-gas and thus raise the PH.

Lowering the TA will indeed help lessen this affect - though it may not reduce it entirely. Adding borates to the pool can also help decrease the PH rise.

PH rise happens much faster at lower PH than higher - so depending on the CH content of your water you might be able to live with a higher PH.

I think most people who find a stable PH with an SWG have low TA, lowish CH and are happy with a PH up around 7.8/8

Regardless - I have an SWG and LOVE it. Adding acid once a week or 10 days is no comparison to adding chlorine daily.
 

chiefwej

LifeTime Supporter
TFP Guide
Jun 12, 2011
3,531
Tucson
I also have extreme evaporation rates, 300+ days a year with very bright sunshine, high CH and high TA in my fill water. I started out needing to add acid every two days. I used acid and aeration to lower my TA from 170 down to 70. Acid additions dropped to every four days or so. Borated the pool to 50 ppm and now I can go more than a week between acid additions.
 

grottoguy

LifeTime Supporter
Aug 24, 2014
462
NJ
Salt changing the PH level is silly.

As mentioned the source of PH rise in pools is TA - which is compounded by the SWG. The SWG causes CO2 to out-gas and thus raise the PH.

Lowering the TA will indeed help lessen this affect - though it may not reduce it entirely. Adding borates to the pool can also help decrease the PH rise.

PH rise happens much faster at lower PH than higher - so depending on the CH content of your water you might be able to live with a higher PH.

I think most people who find a stable PH with an SWG have low TA, lowish CH and are happy with a PH up around 7.8/8

Regardless - I have an SWG and LOVE it. Adding acid once a week or 10 days is no comparison to adding chlorine daily.
When the PB said salt raises the PH he meant a SWG and he was correct. As you said, it causes out gassing of Co2 which causes PH to rise. Their are ways to combat it, but it may cause more additions of acid. You should do a search on this forum of different between an SWG and a Stennar for benefits and cons of each
 

isriam

Well-known member
Jan 15, 2015
197
PHX
I'd trade Chlorine for MA any day of the week. Can put the bottles in my garage and buy 5-10 at a time. Also add less per day than chlorine, and you can skip more days.
 

pabeader

LifeTime Supporter
TFP Guide
May 14, 2015
4,349
Cartersville Ga
Isriam - Just a note: It is not recommended to have MA in the same area as metal. The bottle will vent and have been known to cause rust on yard tools and other metallic objects.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
14,963
Evans, Georgia
I wonder if this PB also warns against fountains, spa spill overs, deck jets and any other water feature that by their nature also causes a rise in pH? Or is he just selective with the warning on the SWG systems?
 

grottoguy

LifeTime Supporter
Aug 24, 2014
462
NJ
If there are any experts on this thread I would be curious to know the relative effects of a SWG compared to a waterfall, bubbler, etc in raising PH.
 

AimeeH

LifeTime Supporter
TFP Guide
Apr 2, 2012
2,028
Columbia SC
I have a SWG, I aerate with a sprinkler to cool the pool a pretty significant part of the summer and I almost never need to add acid........not once this season. My fill water is extremely low TA. I usually have to add baking soda to raise TA once at opening and that is it. So low TA keeps PH from rising too much.
 

Vickery

Gold Supporter
Silver Supporter
Feb 22, 2009
432
Perfection, NC
It all depends upon your fill water. Topping off with high TA water will mean more acid required. Softened water will allow you to maintain an easier balance point. I add 1/2 gal of MA every two weeks. And that's the total of my chemical additions.
 

Griswald

Well-known member
Jul 7, 2014
751
Hope Mills, NC
Number one, dont ever use that pool builder for anything.

I have a SWG pool and bouht a galon of muratic acid last fall. There is about 2 cups left in it. You can get things set up so that your pH holds fairly steady. Its not too difficult.
 

Tul9033

Member
Mar 31, 2016
19
NE OK
I am having a similar issue. A quart of MA every 2-3 days in a SWG 15K River Rok pool. My TA is holding steady at 80 despite the MA additions. If I can't get get the TA down to 50-60 (or if I do and still have high pH) I am considering a Stenner pump for daily MA addition.

My fill water TA is 120.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,445
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
If there are any experts on this thread I would be curious to know the relative effects of a SWG compared to a waterfall, bubbler, etc in raising PH.
It's very hard to say. While the chemistry is fairly straightforward, the process is a mechanical one which depends on the flow of water into the pool, the amount of bubbles created, temperature and whole bunch of other parameters. In it's simplest description you can think of a bubble under water as an entirely unique atmosphere. As the bubble sits in contact with the water, the process of diffusion and equilibrium gas exchange (Henry's Law) is what occurs. Pool water is over-carbonated relative to the atmosphere, so there is a greater concentration of dissolved inorganic carbon in the water than outside of it. When an air bubble sits under water in contact with the solution around it, there is a chemical driving force for the CO2 in the pool water to diffuse into the bubble. The bubble then eventually makes it up to the surface of the water and releases any CO2 is has absorbed along the way to the atmosphere.

SWG's create bubbles of hydrogen gas (very low solubility in water) and chlorine gas (much higher solubility in water). If the hydrogen bubbles sit in the water for a long enough contact time (say a really long run of pipe from the equipment pad to the pool), then most of the chlorine gas generated dissolves into the water but very little of the hydrogen gas does. So, this bubble of hydrogen gas has absolutely no CO2 in it when it forms and there is a huge concentration difference between the inside of the bubble (zero CO2) and the water it is in contact with (at a pH of 7.5 and a TA of 70ppm, your water has almost six times as much CO2 in it relative to atmospheric levels, see this chart by Richard). Thus, the hydrogen bubble can absorb quite a bit of CO2 before it leaves the pool. Water features can generate quite a bit of splashing and bubbles too but I think they often run a lot less (or should be run less) than an SWG.

Again, it's very hard to quantify in exact terms which one would be dominant....
 

chiefwej

LifeTime Supporter
TFP Guide
Jun 12, 2011
3,531
Tucson
I was having to add MA every two days. So, I lowered my TA using acid and aeration from 170 down to about 70. Now, my MA additions were every four days. Borated to 50 ppm and now my pH remains stable for more than a week between adjustments. That's a level I can deal with. With my very high TA in the fill water, I know I occasionally have to readjust the TA, but that's only every few months.
 

sargent

Well-known member
Aug 19, 2013
291
Tulsa, OK
I'm on my third year with a SWG. The first year I used quite a bit of MA until my TA came down (maybe a total of two gallons, but not all at once). Then I added boric acid and my pH was pretty stable so that I only added a couple of cups of MA every 10 days or so. The second year I used a total of 2 cups of MA all summer. I think that is because we received a fair bit of rain, so I did not have to add a lot of fill water. This summer I have used 6 cups of MA so far. I try to keep my pH at 7.5, and if I see it is getting close to 7.8, I add 2 cups of MA. I have done that three times this year.
 

Foosman

Bronze Supporter
Jul 21, 2016
361
Austin, TX
I appreciate all the great responses. I think we are going with a SWG, as we are dealing with kiddos with eczema and they get rave reviews from everyone I can find that owns one. As an aside I had additional conversations with the PB as to what he recommended. He suggests pucks and explained to me that you just partially drain your pool once a year. He never heard of the TFP way. He also runs a pool cleaning company and is shoving pucks in all his customers pools. He claims it is impossible to avoid partial draining. Unfortunately he didn't have a good answer to drought years where it is illegal to drain and fill a pool.