What is an SWCG and what should my settings be?

[divnkd101]

I will be the first on this category. This was some of the information that I was looking for when first looking for a pool. So, here are my questions:

1. What is an SWCG (Saltwater Chlorine Generator)?

2. How does it work?

3. Once I have chosen the process of SWCG, what are the most typical settings to use throughout the year?

4. What are some of the pros and cons to my selection?

[chem geek]

I'm going to try and answer your questions in a (mostly) non-technical way and if I fail, hopefully others on this forum will help you out. My answers are below your questions in dark blue

I will be the first on this category. This was some of the information that I was looking for when first looking for a pool. So, here are my questions:

1. What is an SWCG (Saltwater Chlorine Generator)?

This is a device that will generate chlorine automatically using chloride (from salt) that is added to your pool. Because chlorine eventually breaks down or gets used up and turns back into chloride, you only need to add the salt once initially. The device is plugged into a power source and uses electricity to generate the chlorine in the pool water. Usually, this device is placed in-line in your plumbing as the last item before water gets put back into your pool (i.e. it comes after the pump, filter, solar panels, heater, etc.).

2. How does it work?

It works by a process called electrolysis. This just means that electricity is used to create chemical reactions that would not occur naturally by themselves. The SWCG device contains two sets of metal plates, one of which is positively charged and the other is negatively charged (at voltages ranging from around 6 to 27 volts depending on manufacturer). At the positive plate, chlorine gas is produced, but it immediately dissolves in water to produce the disinfecting form of chlorine (hypochlorous acid) plus hydrochloric acid. At the negative plate, hydrogen gas is produced along with hydroxyl ion. The net result is that chloride ions (from salt) in the water are converted to the disinfecting form of chlorine.

The chlorine produced by an SWCG is identical to the chlorine from other sources, including bleach. However, it only consumes electricity to do this and does not introduce other chemicals into the pool.

3. Once I have chosen the process of SWCG, what are the most typical settings to use throughout the year?

I don't know. Someone else can answer this, assuming you mean setting like how long is it typically on or what power setting is used.

4. What are some of the pros and cons to my selection?

Some of the pros don't have to do with the SWCG per se, but rather with having more salt in the pool (typically around 3000 parts-per-million or ppm -- for comparison, the ocean is around 35,000 ppm). The salt in the pool feels silkier and is less harsh on skin and the eyes (less stinging or drying out). The biggest pro for the SWCG itself is convenience. You don't have to buy chlorine and add it to your pool. It is also more likely for your pool to remain sanitary and to not get algae because the SWCG won't "forget" to add chlorine, plus it does some super-chlorination in the SWCG itself.

Some of the cons include a greater tendency for the pH to rise in the pool, requiring you to add acid relatively frequently. There are methods to reduce this problem, but it is not eliminated and is caused primarily by the aeration of pool water from those hydrogen gas bubbles I mentioned that are produced during the electrolysis. The other main con is the initial cost (usually around $1000) and the cost to replace the cell (usually around $300) which may be needed every 3-5 years. The cost of generating the chlorine is quite a bit less than chlorine from other sources.

Other cons are controversial and not seen in all pools and are mostly due to the increased salt in the pool (not the SWCG itself) and include possibly greater corrosion of soft limestone or other susceptible surfaces (if not sealed or hosed off or resistant to salt water). There may be a greater risk of metal corrosion, especially for salt water dripped onto non-stainless steel in pool chairs, etc. The salt water is more conductive to electricity so may increase the risk of shock (mostly tingling) if the pool is not properly bonded.

For the most part, people who have SWG pools love them and find the convenience very compelling.

[divnkd101]

Thanks for the reply CG. I was hoping people such as yourself would respond to this one. You only tend to get the "GOOD" information from the PB's and not some of the cons. Although, I must say that the Pros definitely outway the cons. Thanks again.

[padrefan]

I have a dumb question....How can you tell when the cell needs to be replaced? Mine's coming up on three years and I can't *see* any difference in it since it was first installed.

[divnkd101]

I have a dumb question....How can you tell when the cell needs to be replaced? Mine's coming up on three years and I can't *see* any difference in it since it was first installed.

Great question. For one, your chlorine production will drop off. Your pool chemistry should start telling you that. I am only into my first year of operation on mine. Hopefully some others will chime in with their replacement stories.

[Auburn_Girl]

Having just read the "con" of salt on limestone, I was wondering if anyone knows what it might also do to travertine. I have just paid to have tavertine coping around my saltware pool and had not even thought of it being a potential problem. I hope someone will comment before I put it down and then wish I had not.
Thank-you

[chem geek]

I don't know if travertine is affected by salt very much, but we have a travertine shower and I can tell you that it requires sealing (with a good sealer) about every 3 years or else it develops mold/mildew. On the scale of stone's ability to absorb water, travertine is a little harder (resistant to water absorption) than average, not as soft as some limestone (though "compressed limestone" is quite impervious to water), but not as hard as granite or marble (especially the "manufactured" versions which aren't original material). A simple test is the "water bead" test -- put a drop of water on the stone and see how long it stays as a bead and when it absorbs into the stone. If the water absorbs into the stone in under one minute, it is very porous; 3-4 minutes is still considered porous; average porosity will be around 10-15 minutes while very hard stones while keep water beaded for an hour or more (which also happens when the stone is sealed).

So my guess, and it's really just an educated guess, is that travertine will be better than limestone in terms of resistance to salt water. If you want to play it safe, you can have it sealed which will make it impervious to water. Our textured concrete hardscape gets sealed every year (and we don't even have a salt / SWG pool). Regardless of the type of pool you have, sealing your stone will make it last longer and look great for many years. The good sealants for stone are quite expensive however (especially compared to the sealants for concrete).

[EDIT] After thinking more about it, I think that if you just periodically hose down areas where there is a lot of splash-out or dripping, such as where you get in and out of the pool, then that will be sufficient. You should probably talk to a stone expert on what they think. That's how we found out what to do with our shower which originally had a very cheap and poor sealant when first installed (the sealant only lasted around 6 months). We now use a penetrating sealant that works well, but a local stone/tile expert should be able to tell you what works best for your particular stone.

Remember that even a regular non-salt pool still has salt in it -- it's just less. At 300 ppm CH, there is around 350 ppm salt (chloride measured as ppm sodium chloride salt) in the pool (with 100 ppm TA and 30 ppm CYA it's a TDS of around 525 ppm). This is because initially most of the chloride in a pool comes from calcium chloride. At 1000 ppm TDS, there is around 825 ppm salt in the pool. So in a pool with 3000 ppm salt (around 3175 ppm TDS), there is from 3.6 to 8.6 times as much salt in the water compared to a typical non-salt pool. So generally speaking, though corrosion from salt evaporation cycles is faster from a saltier pool, the quality of the stone and the care of it are far more important determinants in how long it will last. [END-EDIT]

[maxsrents]

"The other main con is the initial cost (usually around $1000)"

Wow...our pb just gave us a quote of $2300, which is a huge con for us. Is that price way out of line? Any opinions will be appreciated.

[SeanB]

"The other main con is the initial cost (usually around $1000)"

Wow...our pb just gave us a quote of $2300, which is a huge con for us. Is that price way out of line? Any opinions will be appreciated.

I know prices are higher in NJ, but sheesh! You might ask what his cost for installation would be. You can get them online for around $800 I believe. Try to negotiate first.

Have you done a contract yet? I'd let him know that price is too high and you are going to shop around if that is still an option.

[DONNIE]

You can find Pool Pilot Digital systems online for under $900.00 depending on cell size.
It seemed complicated at first but with the manual and the aid of a few experts on these boards now it is so simple to use. It's really a matter of getting it adjusted to your pool size and water chemistry then it just does it's thing. I would highly reccomend it.

Donnie

[chem geek]

My estimate of around $1000 for initial SWG cost was for the cost of the SWG unit itself (approximately) at retail. The labor for installation varies and PBs get the units wholesale so they make money from that as well. People have quoted $1300-$1500 for an SWG installed including labor, but obviously that varies quite a lot depending on local labor rates. Areas with lots of pools and lots of competition, like Phoenix, AZ, have unusually low costs for almost anything associated with a pool while other areas where pools are less common have much higher costs.

Even figuring high hourly labor rates, your quote does seem high. Perhaps it should be broken down more specifically -- how much for the SWG unit itself, how many hours of labor, other parts (plumbing), etc.

[maxsrents]

Thanks for the help! I will definately ask our pb to break down his quote.
We signed our contract 9/06 and the work began 11/06 and we are now waiting on our colored concrete patio and interior plaster finish w/ 3m quartz. When we originally signed we weren't even considering the SWG but after reading more about it-we are pretty certain we want it!!

[drogers]

$2300 is far too high, unless that includes a year of pool service too! I just broke down and went for the SWCG at the last minute when my PB got me a good deal - $150 off my automation and the SWCG for $1k installed (down from the original quote of $1200). I could have bought the same SWCG (intellichlor 40) for 8-900 online, and installed it myself, but the discount from pentair applied to both pieces, so i went for it.

Unless your SWCG option includes an automation upgrade and a better pump, your PB is trying to soak you for about $1000...

[maxsrents]

I just spoke w/ our PB and he uses a Jandy AP1400. Does anyone have opinions on this brand? I did notice that the automatic chlorine feeder is already installed.
Does anyone know of a reputable online retailer for this brand?
Thanks again for all of the help and insight-it really helps to unconfuse a confused newbie.

[divnkd101]

I just spoke w/ our PB and he uses a Jandy AP1400. Does anyone have opinions on this brand? I did notice that the automatic chlorine feeder is already installed.
Does anyone know of a reputable online retailer for this brand?
Thanks again for all of the help and insight-it really helps to unconfuse a confused newbie.

Regarding opinions, this is the unit that is installed on my pool and I have had no troubles with mine. Now my pool is fairly new (Sept. 06). I currently have mine operating at 50% production. All of my water test results dictate the same readouts on my PS-8 regarding salt levels, etc. I am sure that others will jump in that have a little more experience. I do not have any websites to suggest. Good luck in your search.

[TheOne]

New pool owner here..

Chemically does the sodium and chloride stay at constant levels so the SWCG creates chlorine over and over without adding more salt? If the chlorine is disinfecting the pool or evaporating during the day how do you not get higher sodium levels with lower chloride levels? You would think this would cause your ppm of salt to drop and require periodic additions of salt.

[chem geek]

For the most part, the chlorine in the pool gets broken down by sunlight or disinfects or oxidizes and when this happens you end up with chloride ion (i.e. salt). The SWG converts the chloride to chlorine (hypochlorous acid) so the cycle is complete.

So generally speaking, the salt level in the pool remains fairly constant. However, splash-out or backwashing and then refilling with water that is not salty will result in a loss of salt and a lowering of salt level (ppm).

It is true that some chlorine is lost though outgassing, but this amount is very, very small, especially compared with the salt level in the pool. The CYA in the pool not only helps protect the chlorine from breakdown by sunlight, but it slows down its outgassing as well.

By the way, the salt test actually measures chloride level only, though the measurement is in ppm units of sodium chloride.

[TheOne]

For the most part, the chlorine in the pool gets broken down by sunlight or disinfects or oxidizes and when this happens you end up with chloride ion (i.e. salt). The SWG converts the chloride to chlorine (hypochlorous acid) so the cycle is complete.

Odd as you would think when the chlorine is broken down (ie used up) you would be left with the sodium ion (Na) without the chlorine ion (CL).

Works for me though if you dont have to buy bags of salt all the time

[chem geek]

You need to think of the term "used up" as meaning "transformed", not literally disintegrated. Unless you are dealing with nuclear reactions, atoms don't ever disappear or go away. They are always conserved. So the chlorine atom will never go away, but it can be in different forms.

When the chlorine atom is in what we call "chlorine" which in water is really hypochlorous acid or HOCl, the chlorine atom is attached to the oxygen and hydrogen that came from water -- in effect, one of the two hydrogen atoms in water is replaced with the chlorine atom. The chlorine atom in this state has a lot of what might be called "potential chemical energy". Essentially this means that it can participate in powerful chemical reactions that cause organic molecules to break apart and eventually get converted to carbon dioxide and water. In some sense, it is like "burning" -- just like burning wood in a fireplace except that in a pool this is done chemically with a powerful oxidizer (i.e. chlorine) rather than with heat and oxygen (technically, oxygen is an oxidizer, but is weaker than chlorine and needs the heat to make the reactions go quickly).

When the chlorine oxidizes a chemical, it itself gets reduced which means that the chlorine goes from the powerful state into a rather inert state that is called a chloride ion. It is this chloride ion that is part of "sodium chloride" salt. So an SWG takes the inert chloride ion and transforms it (boosts its potential energy) to a higher state in the form of chlorine. Then this chlorine participates in chemical reactions as part of disinfection or oxidation or getting hit by ultraviolet light -- all of which cause the chlorine to give up this potential energy and fall back down to its inert chloride ion state.

I hope that all made some sense.

Richard

[Rob]

I'm sure Chem Geek will correct me if I'm wrong, but here's something how it works (for reference, I have my BSc. in Chemistry, but I'm a non-practicing Chem Geek, having transitioned to Computer Geek (more lucrative )

NaCl + H2O + energy = NaOHCL + H2

NaOHCl exists as OHCl- and Na+ in solution, but I'll write them as associated to you know what happens to the sodium during all of this (basically nothing, balanced in solution)

NaOHCl + stable organic = H2O + NaCl + unstable organic(a hydrogen ripped off)

The unstable organic (ideally, part of a living algae cell) can now continue to react in numerous ways to break down (again, ideally) into CO2 and H2O, but probably not quite that cleanly