Trading bleach for MA w/ a SWG?

[Nectarologist]

Hi. I was planning on getting a SWG but have some reservations about needing to add muriatic acid. It seems some people are adding it a lot. Am I saving that much time with the SWG if I need to be concerned about the pH, and going to buy it like I do bleach? As it is now my pH was balanced at the start of the season and I test it regularly and have never needed to do anything else with it.

 

[tlevy]

You need less MA by volume than bleach, and generally don't need to add daily, vs daily bleach requirement with nonSWG.

Others more schooled will probably weigh in here, but that is my experience


18000 IG, SWG, 1/2 HP Tri Star + Solar PV direct DC Lorentz pump, Sand filtrt

 

[yann]

Hi

It's true that with a SWG, pH tends to creep up due to aeration.
However this could be managed with a lower TA.

I haven't added any MA to my SWG pool in 3 weeks and my pH is stable at 7.4-7.6

 

[JamesW]

SWGs are pH neutral. They do not raise pH.

Any pH rise is due to carbon dioxide offgassing. Lower TA (about 60) and higher pH (about 7.8) will reduce pH rise very close to zero.

If you have a high TA fill water source, that can create TA rise and pH rise.

SWGs create minor aeration and can create some pH rise if the pH is kept too low or the TA is kept too high.

 

[JoyfulNoise]

Even with my high TA fill water and multiple sources of aeration (waterfall and spillway), my acid addition frequency is 7-10 days. I used to get 14 days but my CH is very high now so I have to maintain a lower pH level than I like to in order to keep CSI in range. I have a cheap source of acid that supplies in refillable 1 gallon jugs so the overall expense is about $30-$40 worth of acid the entire season.

That’s A LOT easier than liquid chlorine dosing in my book...

 

[YippeeSkippy]

I've only added MA to my pool twice this summer. My pH likes to hang at 7.8 it seems. That's within normal range (7.2-7.8) so I don't sweat it. I don't have any special water features that encourage pH rise either, so that helps.

Maddie

 

[needsajet]

I like not lugging all the liquid around (store to car to shed to pool). During my first year, the SWG produced chlorine equivalent to about 500 lbs of 12.5% chlorine. I used 50 lbs of 32% acid.

You may have bumped into the Wikipedia article - Salt water chlorination - Wikipedia - which is wrong on many counts. That article includes significant errors, particularly with respect to conversion of chloride ions to free chlorine, and also the comments suggesting that hydrochloric acid is required to "balance" the replenishment of free chlorine.

 

[peirek]

Aren't borates an option to help buffer the pH rise?

 

[Bandit5]

I was in the same boat a few months ago. I decided to install a Stenner pump instead. See signature for details. I chose it over the SWG for the following reasons: 1) Cost of SWG was much higher, 2) Eventual replacement cost of cells, and 3) Didn't want to deal with more acid. Apparently not all SWG experience an increase in pH, which I did not know before. With the Stenner pump, I add a 5-gallon carboy of 12.5% chlorine every few weeks. Personally I find handling chlorine much easier than handling MA. I use it enough in my spa and the fumes can be really irritating. I would still consider a SWCG as a viable option though.

 

[Perpetual summer]

With my pool my TA rose to 120 and my PH stayed at 7.6 all summer, this past week it rose to 7.7. I keep solar cover on when not in use.

 

[JoyfulNoise]

One has to be careful when saying the "cost of this" is less than the "cost of that". As it turns out, the cost of running an SWG and the cost of using liquid chlorine dosing (whether by hand or stenner pump) are practically equivalent. See here - Economics of Saltwater Chlorine Generators. With an SWG, you are simply purchasing all of your chlorine up front whereas with liquid chlorine, you are distributing the cost of chlorine over much smaller increments.

It is certainly true that installing an SWG will cost you a lot in terms of up front costs; so if you don't happen to have $1,000-$1,500 in your savings account, it can be a harder choice to make.

Pay me now, or pay me later.... as the saying goes.

 

[JamesW]

Aren't borates an option to help buffer the pH rise?

Borates and cyanurates provide alkalinity that does not create carbon dioxide.

For a pool with 60 TA, 7.8 pH, 50 ppm borates and 60 ppm CYA, the TA is 25 ppm carbonate, 14 ppm borate and 21 ppm cyanurate.

25 ppm carbonate alkalinity and 7.8 pH creates low enough carbon dioxide that you should not have any pH rise.

 

[Bandit5]

One has to be careful when saying the "cost of this" is less than the "cost of that". As it turns out, the cost of running an SWG and the cost of using liquid chlorine dosing (whether by hand or stenner pump) are practically equivalent. See here - Economics of Saltwater Chlorine Generators. With an SWG, you are simply purchasing all of your chlorine up front whereas with liquid chlorine, you are distributing the cost of chlorine over much smaller increments.

It is certainly true that installing an SWG will cost you a lot in terms of up front costs; so if you don't happen to have $1,000-$1,500 in your savings account, it can be a harder choice to make.

Pay me now, or pay me later.... as the saying goes.

That is true. But the operating costs between the two are difficult to compare. Yes, you have to purchase chlorine with a Stenner pump, but you also need electricity to run both pumps. I am unable to find the power draw of a Stenner pump, but I would bet that it is lower than the SWCG, how much lower and the cost difference the two I don't even have a guess - if it is lower at all. And the eventual repair. Would I spend less on chlorine than the ~$750 I would need to replace the cell in an IC60? (What I would need for my pool) Yes, it is possible if it lasts for many years. But if I only get two or three seasons out of it, maybe not. Replacement parts for a Stenner pump are much cheaper by comparison, even replacing the entire unit is still much less expensive.

But you are right, depending on your outcome and your specific requirements, it is difficult to say that a Stenner is cheaper overall.

 

[needsajet]

In case it helps with your comparison, power for the Stenner is negligible/near zero (small motor and intermittent use). My SWG ran 1150 hours last year and draws 110 watts. I pay $0.23 for a kWh, so that's about $30 per year.

Some people get very short life from a SWG cell, but an IC60 in a 22K pool should last for 7 or more years providing 2.5 ppm FC per day for six months. The shoulders of the swim season require less FC, so that figure is probably more like 10+ years. The key to long cell life is balanced water (and no dry acid) so that the cell doesn't need any acid-cleaning. Another factor is owners that allow a nascent algae bloom to exist and run the SWG harder to keep the algae from showing up as a green pool. Both issues can be avoided by using TFPC.

 

[CaptainCannonball]

No doubt every situation is different.

When I did the research for my situation, the salt cell that matched my Jandy automation had a rating of 6 amps but operated at 1.25 amps at 230v for 289 watts an hour. The cost of having to run the SWG 6-8 hours a day and the pump an extra 4-6 hours a day quickly pushed energy consumption over $2 a day with $0.39/kWh energy costs.

Then I thought about how convenient not lugging jugs would be. This started to be offset with the additional maintenance of salt testing, salt replacement (because we have pretty substantial splash out) and periodic cell cleaning/replacement. I also factored (possibly incorrectly) additional muratic acid demand and that made the decision easy.

For us, the electricity costs basically would cost the same as buying the bleach. When we put pool solar panels up and run higher pump speeds and longer durations anyway, the pump electricity costs get dropped from the equation making a SWG more desirable.

Then there is that whole winter thing where I have to use bleach anyway when water temps drop. In that case, I would still have to manually dose bleach (albeit not as frequently) during the cold months. It sure is nice to fill up the Stenner, set it and forget it.