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Thread: Is there an SWG primer?

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    Gooserider's Avatar
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    Is there an SWG primer?

    Is there any sort of a "primer" on this whole SWG subject - I keep seeing references to them, but am not really clear on what they are / how they work / what they do and so forth... Obviously they make chlorine, but... It might even be worth a sticky?

    Some of the questions that come to mind...

    1. How salty are we talking about making the water - is it on the order of measurable but not noticeable to swim in, or is it like going to the ocean instead of the lake? How much of a problem is the salt going to be if one just backwashes out on the ground (like I currently do with my DE filter) (i.e. will it kill my grass / trees, pollute the ground water, etc?)

    2. In general numbers how expensive is it to put one in and run it? How does this compare to running straight "pool store" chemistry or BBB? How do the cost / amounts of chemicals involved change? What does it cost to run one in added electricity? What about parts to keep it going?

    3. Does it cut back on the amount of time needed for testing / working on the pool?

    4. I've seen discussion about turning an SWG down / off in the winter, but the people doing it were still leaving their pools set up mostly - what about those of us in the frozen north lands that have to tear everything down, blow out the pipes, etc. to avoid freezing in the winter?

    5. What sorts of changes to plumbing / electrical are needed? Currently I have two 15A 110v circuits to the pool, one for the main filter pump, one for the Polaris booster pump, each is controlled by an Intermatic timer next to the breaker box - would these work, or would I need another dedicated line (which would get expensive, as my breaker panel and conduits are both full....)

    6. Any other stuff on the upsides / downsides of having one that I haven't thought of, but that you'd tell a person considering the idea?

    Gooserider
    Free-form Inground gunnite pool, Estimated 16-17K gallons. New Pentair TR60 ClearPro 24" sand filter and Compupool CPSC-48 SWG, Hayward SP1607X10 Pump w/ 1HP motor, 1.5" plumbing, Polaris Pressure cleaner w/ booster pump. pool is more than 25 yrs old, less than 35. Not painted, deteriorating tile surround. I am paraplegic, get in/out of pool w/ S.R. SMITH PAL portable pool lift (significantly modified)

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    JasonLion's Avatar
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    Re: Is there an SWG primer?

    1) Most SWGs call for salt levels around 3000, far below typical ocean water which is around 35,000. Most, but not all, people can just barely taste salt when the salt level is around 3000. Most people also say that slightly salty water feels better on their skin then plain water. Salt at that level is not normally a problem for plants. A few plants are extremely salt sensitive, but they are rare and if you had one you would probably know that already.

    2) Prices vary quite a bit. A typical in-ground SWG is around $800, but they come significantly cheaper and significantly more expensive. Electricity is trivial, the main cost is replacing the cell every two to four years. The average cost over several years is typically more than for pure BBB but less than for pool store chemicals.

    3) A SWG will usually save you time on testing. Once everything is setup and working you can often test the water every other day or sometimes less, instead of every day.

    4) You winterize the SWG the same way you would any other part of the plumbing. Make sure you get all the water out of the pipes and you should be fine.

    5) In almost all cases you can simply wire the SWG to the pump side of the pump timer and leave it at that. The SWG should be off when the pump is off, and on when the pump is on.

    6) In almost all cases, people who get a SWG love it and don't have problems. Some people with natural stone work have had problems with the stone, apparently because of the salt in the water. This is quite rare, though more common in a few specific areas. There is a long running, unresolved, debate questioning if the salt actually has anything to do with the reported problems.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Gooserider's Avatar
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    Re: Is there an SWG primer?

    Thanks, I appreciate the replies - I don't know that we'd get one if we keep the current pool hardware setup, but it definitely might go on the list if we decide to make major changes...

    A couple of other thoughts

    1. Our current DE filter says "Fresh water ONLY" on the label - would an SWG be a problem for this filter, (or would it limit replacment filter choices?) or is the salt level low enough that it's still considered fresh water?

    2. How does the water in an SWG setup compare to typical chlorine only pool water in terms of corrosion potential? I know sea water is nasty stuff from a corrosion standpoint, and chlorinated water is no great thing either - aside from the possible stone problem you mentioned, would an SWG cause any extra constraints on materials allowed in the pool or near it - i.e. metals used in pool plumbing, heat exchangers or something like that? Or potentially making the poolside BBQ grill rust out sooner?

    Gooserider
    Free-form Inground gunnite pool, Estimated 16-17K gallons. New Pentair TR60 ClearPro 24" sand filter and Compupool CPSC-48 SWG, Hayward SP1607X10 Pump w/ 1HP motor, 1.5" plumbing, Polaris Pressure cleaner w/ booster pump. pool is more than 25 yrs old, less than 35. Not painted, deteriorating tile surround. I am paraplegic, get in/out of pool w/ S.R. SMITH PAL portable pool lift (significantly modified)

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    JasonLion's Avatar
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    Re: Is there an SWG primer?

    Salt levels around 3000 are counted as fresh water.

    There are materials that will rust out. In almost every case they will rust out with or without salt. Typically they rust more quickly with salt than without, but they are going to fail either way. The swimming pool industry already knows not to use these materials. Every now and then someone skimps on materials and you get a part made of inferior materials that rusts out, but that is rare and will happen eventually with or without salt.

    The extra salt does increase the corrosion potential, but not by very much at all. Salt around 3000 is nowhere near the corrosion potential of ocean water. Also, keep in mind that there is always some salt in the water, even if you never add any. Most of the chemicals you add to the pool end up adding salt. Chlorine essentially turns into salt after it is used up disinfecting contaminates. It is common for a non-salt pool to have salt levels over 1000.

    The largest risk is for places where splash out evaporates and salt accumulates over time, like the edges of a waterfall. If you wash those places off occasionally that will normally take care of it, but if enough salt accumulates, there can eventually be damage in those spots. This is usually only a problem in areas with low rain fall combined with situations, like waterfalls, that cause a lot of splashing that evaporates.

    The vast majority of pools never see any damage from SWG levels of salt, even after many years. About the only situation that I would worry about is where you have put huge amounts of money into natural stone work that is not underwater and is constantly getting splashed on (think waterfall).

    Comparing the corrosiveness of salt to chlorine is tricky. They tend to affect different materials in different situations. Chlorine used with CYA, as should be done in any outdoor pool, causes very little corrosion. Chlorine used without CYA, as is often done in indoor pools, is far far more corrosive. Even then, the materials used in swimming pool construction are normally fine.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Gooserider's Avatar
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    Re: Is there an SWG primer?

    OK, sounds good - I guess I was just being paranoid about the salt in some ways, as I spend much time messing with boats as I was growing up, and saw the tremendous difference in how stuff held up that was used in fresh water as opposed to salt.

    However the GF may need more convincing - she is quite willing to give BBB a try, but doesn't see what an SWG gives to justify the up front cost.

    Either way, thanks for the info. It will help me better follow some of the other discussions (And I still think it might either make a good sticky, or possibly rework into an "SWG 101" article for the Pool School)

    Gooserider
    Free-form Inground gunnite pool, Estimated 16-17K gallons. New Pentair TR60 ClearPro 24" sand filter and Compupool CPSC-48 SWG, Hayward SP1607X10 Pump w/ 1HP motor, 1.5" plumbing, Polaris Pressure cleaner w/ booster pump. pool is more than 25 yrs old, less than 35. Not painted, deteriorating tile surround. I am paraplegic, get in/out of pool w/ S.R. SMITH PAL portable pool lift (significantly modified)

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    Re: Is there an SWG primer?

    Goose,

    good to see you here as well, that hearth.com site can be hard to get away from. I use a SWG on my AGP and love it. We only bought our pool last year and after some research here, we went out and purchased the SWG. The pool was great all summer! At the end of the year we just dumped all the water into the tree and have seen no ill effects. I will be watching closely this spring to make sure all trees are OK. If not the BIS will get them!

    North of 54th
    -inBamaNow

    16x32 Hydra Liner, Hayward 24" Pro Sand Filter, WhisperFlo 1HP Pump, Hayward CL200, AquaChem Test Kit =[

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    Gooserider's Avatar
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    Re: Is there an SWG primer?

    Quote Originally Posted by donnest
    Goose,

    good to see you here as well, that hearth.com site can be hard to get away from. I use a SWG on my AGP and love it. We only bought our pool last year and after some research here, we went out and purchased the SWG. The pool was great all summer! At the end of the year we just dumped all the water into the tree and have seen no ill effects. I will be watching closely this spring to make sure all trees are OK. If not the BIS will get them!

    North of 54th
    Thanks... (Though I do have to mention that it was a thread on the Hearth that got me over here - I've found asking for pointers to other relevant boards can be a really helpful thing for everyone )

    Gooserider
    Free-form Inground gunnite pool, Estimated 16-17K gallons. New Pentair TR60 ClearPro 24" sand filter and Compupool CPSC-48 SWG, Hayward SP1607X10 Pump w/ 1HP motor, 1.5" plumbing, Polaris Pressure cleaner w/ booster pump. pool is more than 25 yrs old, less than 35. Not painted, deteriorating tile surround. I am paraplegic, get in/out of pool w/ S.R. SMITH PAL portable pool lift (significantly modified)

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