Downsides of SWGs - fact or fiction?

[Vickery]

I did the TA reduction per the TFP instructions, added the borax and ma, then installed an Intex 8110. After spending 5 years of fighting algae and listening to the pool store people (nice folks...but their agenda is to sell stuff, not keep my pool clean) we have sparkling clear water (guests marvel at it and declare that they would never spend all the time they think is required to get it so bright.) I vacuum once a week, add a qt of ma twice a month. Ph - 7.6, tc 7. I'm almost embarrassed by how easy it is to keep the pool sparkling. The swg runs 2 hours per day. Granted, the chlorine load isn't high other than from rain debris.
After 25+ years in industrial system design and sales, the idea that slightly saline water is so corrosive compared to chlorinated water is really a joke. Chlorinated tap water is used as a baseline for corrosive resistance. Water itself is THE universal solvent. Proper water balance is key. Salt can build up on aprons...but here at the coast it can build up on anything and everything. When we had to replace the liner we got to start with new water. No puck residuals, no left overs from whatever the pool store folks recommended. Just TFP advice. And now a CLEAN, TROUBLE FREE POOL! If salt buildup is a concern...wash it off! If the flagstone (or bluestone, or tile, or whatever) is soft enough to suffer from a little salt then seal it with a stone sealer. It's too easy now for me to ever go back!

THANKS, TFP!!!

 

[Brad S]

If the flagstone (or bluestone, or tile, or whatever) is soft enough to suffer from a little salt then seal it with a stone sealer.

Yep, thats what i did. Pretty easy to do. IMO, any stone coping should be sealed, regardless of salt or not.

 

[Beez]

It's clear that with SWGs it's VERY important to keep T/A at the low end of the range or lower (around 80ppm) or you'll face the constant rising pH problem.

I can vouch for the fact that rising PH is not just a problem for SWGs. I manually chlorinate with bleach and had a persistent rising PH until I lowered my TA to 50-60. Even with the lower TA, I still have to add acid regularly, just not as much.

 

[Durk]

I have considered an SWG for the convenience but I believe the cost implications make it a no-go in my particular case. I have an oversize single speed 1.5 hp pump on a system with all 2" lines and no spa or features. A 4-hour run (two in the AM for skimmer cleaning and two at night at chem time) keeps the water crystal clear and is one turnover. My NJ electric rates are brutal; 8-hour runs were killing me back in 2004 when I started cutting back and they are much higher now. Aside from the installation cost of the SWG, I would need a variable speed pump as well, plus probably a controller, and still face increased electric use for the cell and more pump time. I'll look again when this pump goes, but for now I'll stick to LC. $18 per month for six months for LC (5 gal 12%) plus maybe 3 gal per year of MA at $7 each plus a manageable electric bill says I can do without the 'convenience'.

 

[Brad S]

How much is a KW of electricity in NJ? I pay 9 cents in Mass.

 

[JohnT]

How much is a KW of electricity in NJ? I pay 9 cents in Mass.

Here's a link to state-by-state numbers http://www.neo.ne.gov/statshtml/115.htm

Massachusetts is a little different than other states, since delivery and actual power are charged separately. For example, Mass avg power cost is a little less than 10 cents a KWh, but service costs about 8 cents a KWh, yielding one of the highest rates in the nation. That's excluding some programs that can reduce costs to individual homes. About double what I pay NJ is high too.

 

[Brad S]

Not sure that chart is exactly correct as parts of california pay over 40 cents.
As for Mass, the generation charge is 9 cents to 12 cents depending on the provider. The transmission charge is not unique to Mass either. Also, its not a one to one charge. In other words, one kW in generation charge at 9 cents is not 8 cents per kW in transmission charge (it's not linear).

 

[chem geek]

OK, now the question for those of us in Texas who have flagstone but do not have SWG's... how much salt does it take to have this effect?

I can see my waterfall is decaying, I see sand in the pool below it -- is it the salt I have due to bleach or is it due to adding MA to control pH?

Bleach will add to the salt level (ALL sources of chlorine increase the salt level, but bleach and chlorinating liquid do so twice as quickly). The Muriatic Acid will increase chloride, but at some point you are probably adding (intentionally or via evaporation/refill) to TA and that usually increases sodium (or calcium and magnesium if from refill). The bottom line is that overall salt levels increase from continued use of chlorine unless you dilute the water.

However, unlike CYA when using stabilized chlorine, the proportional rate of increase is a lot slower. At 1 ppm FC per day, Trichlor would increase CYA by over 100 ppm in 6 months while bleach or chlorinating liquid would inrcrease salt levels by almost 300 ppm in that same time period. 100 ppm CYA is a lot worse in its side effects than 300 ppm salt. Also, in terms of water dilution, a dilution of 5% of the water will reduce a CYA level of 50 to 47.5 or about 4 days of Trichlor use (at 1 ppm FC per day) while it will reduce a salt level of 1000 by 50 or about a month of bleach or chlorinating liquid use.

As for what level becomes a problem, that's a very hard question to answer. For stone, it's probably roughly closer to a linear relationship -- twice as much TDS, then twice as much salt splashed out. Then water evaporates and the salt recrystallizes. What makes this more complicated is that the type of salt matters in terms of the kind of damage that can be done. It looks like magnesium sulfate is the worst offender so if one has hard water and one uses dry acid or non-chlorine shock (MPS) which both increase sulfates, then that is probably worse.

Richard

 

[waste]

FIELD REPORT-

The company I work for has well over 100 SWCG units installed (the oldest being ~ 6 years) I haven't seen the pH rise that I expected on the pools we've built. The only theory that I can come up with is that we have 8 - 12 returns on any given pool (more if there is a spill over spa involved) and that releasing the hydrogen gas byproduct through that many returns keeps the aeration to a 'dull roar'. I also follow Waterbear's advice and keep the TA ~ 70 - 80. I could count on one hand the number of pools I've had to go out and dose with muriatic acid because the pH had climbed too high.

My apologies, Waterbear. I did not gear my advice toward the few people who actually care to research anything (TFP users). I work with customers and clients around the L.A. area; fast paced, instant gratification lifestyles for the most part. So, all I ever deal with on swgs, day in and day out, are problems. SO, if done as you do, SWG's would be great! If I tell my customers (even the DIY-ers), or write out instructions for even the simplest things, I usually get these blank stares... I'm happy to work for a new pool company, though, where the customers just tell us to "do what needs to be done," rather than the thousands of DIY-ers with NO experience I had to re-explain EVERYTHING to, regularly! If only every DIY-er used TFP...

Dude I feel your pain I've tried to get so many of our customers to understand the need for at least weekly maintenance/ testing, but they just won't do it Also, I've given ~ 20 customers this site and, while they all seemed sincere in REALLY wanting to take control of their pools, not a 1 of them has ever shown up here - I'm risking my job to help them and they won't even follow the best advice I can give them

As for salt damage, SWCG owners need to keep a hose handy and rinse off the deck, chairs and any other poolside metal after folks use the pool

Thanks for the thread

 

[kln]

Corrosive to Flagstone - is a sw pool corrosive to concrete? We have a faux rock waterfall and faux rock coping around our pool all made of colored concrete. We have been considering a swg. Would it be corrosive? Thanks!

 

[Strannik]

Aside from the installation cost of the SWG, I would need a variable speed pump as well, plus probably a controller, and still face increased electric use for the cell and more pump time.

SWG has nothing to do with this. You can buy SWG which will satisfy your needs with this run time. This is, in fact, what we suggest to our customers with big pumps - buy a higher output model.

If 4 hours is enough to properly chlorinate your pool using bleach, it will be enough to chlorinate it using the SWG with equivalent output.

 

[Guest]

Corrosive to Flagstone - is a sw pool corrosive to concrete? We have a faux rock waterfall and faux rock coping around our pool all made of colored concrete. We have been considering a swg. Would it be corrosive? Thanks!

not that I have ever heard of.

 

[kln]

thanks waterbear!

 

[cobra46]

Not sure that chart is exactly correct as parts of california pay over 40 cents.
As for Mass, the generation charge is 9 cents to 12 cents depending on the provider. The transmission charge is not unique to Mass either. Also, its not a one to one charge. In other words, one kW in generation charge at 9 cents is not 8 cents per kW in transmission charge (it's not linear).

These number could very well be correct. The chart says 'across all sectors'. Commercial power rates are far far lower than residential rates.