Pros and cons of SWG

[Brendon]

I have seen many comments about "SWG is the way to go", etc. I am interested to hear what the pros and cons are.

Thanks!

 

[Eauclaire]

In Canada, Toronto has a bylaw forbidding pool salt water discharge directly to the storm drainage (i.e. the street) system, so salt water pool owners have the option of either connecting to the sanitary system or trucking the water out. A number of companies now refuse pool closures for fear of legal reprisals.
These rules are simply an extension of snow-discharge regulations, which forbid the direct dumping of salt-ladened snow to water bodies. Snow clearing operators use discharge sites, which consist of retention ponds, to protect the St Lawrence River ecosystem.

 

[JoyfulNoise]

I would say that the biggest PRO, in my opinion, is that the SWG (like other types of injection systems) acts as a constant source of FC in your water as opposed to adding chlorinating liquid in one large bolus dumped in all at once. It also works without complaining about weather or if "the game" is on or if it just doesn't feel like getting off the couch....in other words, it's the consistency I like.

The downside....ABSOLUTELY NOTHING!!! Ok, not true. SWG's do affect your water chemistry in other ways. Typically, you go from having to add bleach everyday, to having to add acid more frequently than normal because SWG's will often raise pH over time with use. As well, since the cell is sensitive to calcium scale, if you live somewhere with hard water (high CH), it's adds to the list of things you have to manage.

As for cost comparisons, well, that horse has been beaten to death. Whether you use liquid chlorine everyday or an SWG, the costs differences are minimal. See Economics of Saltwater Chlorine Generators by chem geek.

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In Canada, Toronto has a bylaw forbidding pool salt water discharge directly to the storm drainage (i.e. the street) system, so salt water pool owners have the option of either connecting to the sanitary system or trucking the water out. A number of companies now refuse pool closures for fear of legal reprisals.
These rules are simply an extension of snow-discharge regulations, which forbid the direct dumping of salt-ladened snow to water bodies. Snow clearing operators use discharge sites, which consist of retention ponds, to protect the St Lawrence River ecosystem.

Interesting. Can you simply "water your lawn" with pool water backwash?

 

[Eauclaire]

Yes, you can! But I was thinking of the autumn drawdown, which is more volume than back washing.

 

[wayner]

I have had a SWCG since I had my pool built about 8 years ago. I live in Toronto so the pool is covered from mid October to mid May. Once my pool isn't opened in May I have to add salt to get to 3000 ppm and CYA to get to about 60 and then there is very little else to do. I just added a bit of MA this past week as my pH has edged up to 7.8.

It may be sacrilege on this site but, at least for me, my pool is pretty much set it and forget it.

 

[4knights]

I have had a SWCG since I had my pool built about 8 years ago.

It may be sacrilege on this site but, at least for me, my pool is pretty much set it and forget it.

I do test my levels most weeks, but the swcg is a set and sim deal for us too. Only add salt if lots of rain or splash out occurs. Only Con- temp has to be above 50-60f otherwise it's fantastic!

 

[wayner]

I never have to add salt in the season as the dilution caused by rain is never enough to move the needle as it is a very small percentage of the volume of water - same for splashing. Regarding temps - when it gets that cold it is time to close the pool.

 

[chiefwej]

I do test my levels most weeks, but the swcg is a set and sim deal for us too. Only add salt if lots of rain or splash out occurs. Only Con- temp has to be above 50-60f otherwise it's fantastic!

Since the OP is in Alberta, I'm pretty sure when his water drops down to 50f (10c) he won't be swimming, he'll be closing the pool for the season

 

[ping]

SWGC Pros and Cons
Pros:
1. Convenience, it eliminates buying, handling, and storing chlorine.
2. Pool is more stable with a constant supply of chlorine which makes it less likely to need SLAM the pool.
3. Able to go on vacations with less risk of pool developing algae.
4. Some people save money on the cost of chlorine over the lifespan of the SWG, but mostly we say it is a break-even deal.
5. Improved water feel from the salt, which can also be added to any pool.
Cons:
1. Upfront cost is high.
2. Pool might use more muriatic acid due to rising pH. Helps if you follow TFP SWG recommended levels for SWG’s.
3. Repair cost of parts that need replacing.
4. A few places have rules regarding the draining of water from SWG pools.
5. Can cause corrosion of soft stone and cheap metal.
6. Very few dislike the salt taste of the water.
7. Some people need to increase pump run time to make enough chlorine.
8. More difficult to SLAM the pool due to higher CYA level.

 

[Pool Tool]

Chief, I think 4knights mentioned the temp to set the expectation that while opening (and closing) the pool the OP will still have to add FC by some other means, hopefully liquid chlorine. Often springtime posts reflect people concerned that their SWCG isn't working and questioning replacement but really the water just hasn't warmed enough for it to work efficiently.

I think the cool water can also cause the cell to report erroneously low salt levels, which need to be verified by an independent dip test rather than dumping in more salt.

Thanks to all for the information as I'm hoping to get a SWCG installed next season. My kids are allergic to chlorine...just kidding. I know its still chlorine, but I wanted to poke fun at all the bad info out on the web.

 

[wayner]

When opening your pool it is generally extremely green or brown so you do have to seriously dose it with Cl to get it cleaned up. Then I guess it depends on the time of year and whether you bother heating the pool. I now have a solar heating system so as long as it is sunny I should be able to keep my pool in the 60s and I also have a NatGas heater so we keep the pool in the 80s during swim season and even in the tails of the season it won't get below 70.

 

[Chuckiechan]

Because my SWG system is always on when the pump is running, it runs a lot since I have pool solar. As a result my chlorine levels are always high.

Since I borated my pool this year my life has been pretty much problem free, acid use is down, and algae is non existent.

You are trading schlepping chlorine for schlepping acid, but trips are fewer and far between in my case.

 

[wayner]

Can't you turn down your SWCG? Mine has a percentage setting where I can have it on from 0-100%. I also have solar so my pump runs from 0600-21000. I just adjust the percentage on the SWCG accordingly.

 

[jmhjgh]

Are you talking about a new build or adding it to an existing pool? I ask because if you go SWCG, you may need to change your diving board stand, basketball system, etc because of salt water corrosion. If you are building new, you can specify materials correctly and not have issues.

 

[Agent99]

Timely thread. I've just now been thinking about a SWG even though I dismissed them a few months ago with my pool remodel.

The hunt for good-priced chlorine is getting a bit tiresome and I haven't even done it for that long. We have a Wallyworld close by even but it is a nightmare in terms of traffic (horrible, awful ingress/egress to this place) to go there so I avoid it like the plague.

 

[Eauclaire]

What determines the optimal CYA level in a salt water pool? If a seasonal pool is always shaded, does it need as much CYA, as a pool in full sun? Does higher CYA reduce wear on the SWG?

 

[JoyfulNoise]

What determines the optimal CYA level in a salt water pool? If a seasonal pool is always shaded, does it need as much CYA, as a pool in full sun? Does higher CYA reduce wear on the SWG?

See this post by mas985.

See the "Certified Pool Operator (CPO) Training - What is not taught" thread and this post.

Basically, with an SWG, you set the CYA level higher in order to generate more bound chlorine (larger reservoir). This allows you to turn down the SWG % power on the cell which has the effect of extending cell life AND reducing the pH rise associated with SWGs. The trade-off (down side) is that your shock level is much higher (~28ppm) should you ever get in trouble.

I know this to be true in my pool by experience. Whenever my CYA falls to 50ppm or lower, my chlorine usage goes way up as measured by % ON-time - that is, I have to run at a higher % output in order to maintain the proper FC/CYA ratio. The difference can be as much as 15-20% on the cell.

 

[chem geek]

The higher CYA is only needed if the pool is exposed to sunlight. So if you have a pool that is always shaded, then you don't need the 80 ppm CYA for the SWG. Indoor pools with an SWG can have a low 20-30 ppm CYA, for example.

When there is sunlight, the savings from the higher CYA level comes from a non-linear CYA shielding effect protecting lower depths from the UV in sunlight. So even at the same FC/CYA ratio, so same amount of unbound chlorine, and the higher FC so higher bound chorine level, the net result is a lower absolute chlorine loss. See this post for a rough estimate of this effect and realize that the loss is varying by CYA level only because of sunlight. If there is no sun, then the loss will not vary much since the unbound chlorine (FC/CYA ratio) is the same. In fact, if anything the loss without sunlight may be a little higher at a higher CYA level due to the slow oxidation of CYA by chlorine (hypochlorite ion).

 

[Semi-retired]

Agree with the above "pro's and con's" - for me, peace of mind when going away for several days is a big plus. In the past with non-SWG pools, I either had to have a pool service take care of it, or a very good neighbor, even if it was only throwing a couple of pucks in the skimmer. Now, can be gone a week or more without much worry. I hated keeping a lot of chlorine products around in my pre-SWG days. They are corrosive (pucks, granulated shock, liquid containers that have been opened) and can actually corrode items if left in a low-ventilated environment.

With that said, besides getting rid of all of those chlorine products, I basically switched from using 20 Mule Team to raise pH in my previous non-SWG pools, to using muriatic acid to lower pH. Besides the SWG I have waterbowl features which tend to drive pH up, so I end up using a fair amount of muriatic acid. However, while I keep the pool parameters at the TFP recommendations for a SWG pool, I haven't as yet "borated" my pool, so perhaps that will help with pH since it should help cut down on chlorine loss (I think), which cuts down on SWG "on" % which should help lower pH rise.

 

[chem geek]

However, while I keep the pool parameters at the TFP recommendations for a SWG pool, I haven't as yet "borated" my pool, so perhaps that will help with pH since it should help cut down on chlorine loss (I think), which cuts down on SWG "on" % which should help lower pH rise.

It's the higher CYA level of 80 ppm that cuts down on chlorine loss from sunlight and lets you turn down the SWG % ontime. The use of 50 ppm Borates just adds additional pH buffering so that the rate of pH rise is slower though it shouldn't reduce the total amount of acid that you need to add. The Borates are also a mild algaecide so if your pool was on the edge of having algae growth, then that would help to lower chlorine usage and therefore lower the % ontime, but the better way is to make sure the FC/CYA level is correct and if necessary kill off any algae first. You can also lower the amount of acid needed from the carbon dioxide outgassing from the waterbowl features by having a low TA level. If you go lower than the recommended levels for TA, you can compensate with a higher CH level. Also, having a higher pH target helps reduce carbon dioxide outgassing.