SALT POOLS feedback please

[chem geek]

Sean,

As you know from other posts on this forum, many (but not all) SWG users experience rising pH which requires regular additions of acid to maintain pH (and possibly adding baking soda to maintain TA over a longer period of time). Non-SWG users using BBB or liquid chlorine do not generally see the pH rise unless they have high TA, low pH, aeration from water features, or a new plaster pool (that is curing). waterbear (Evan) has found that using 50 ppm Borates significantly reduced this acid demand, possibly by reducing chlorine demand and allowing for lower power levels or run times of SWG generation. We never definitively determined the cause of this pH rise but I believe it due to the hydrogen gas bubbles causing aeration to outgas carbon dioxide (the other primary candidate is outgassing of undissolved chlorine gas bubbles, but I find that less likely). Users who have tried running at lower TA levels (and avoided lower starting pH) have had less acid demand as well which is consistent with the carbon dioxide outgassing theory. I suggest that SWG manufacturers experiment with different approaches to managing the hydrogen gas bubble production, possibly segmenting or otherwise capturing the flow of hydrogen bubbles through the outlets so that they have less contact time with pool water or varying bubble size (if possible) since larger bubbles should be less effective at pulling carbon dioxide out of the water.

The issue that dawndenise has raised is valid in that normally SWG systems do not experience algae, but when they do you need to shock with a heck of a lot of chlorine due to the high CYA (70-80 ppm) recommended by most SWG manufacturers. Though the superchlorination effect in part of the volume of water through the cell seems to keep algae at bay for most users, it isn't perfect and the high CYA and typical recommended FC level (3 ppm) from the SWG manufacturer means a disinfecting chlorine level that is sufficient for sanitation, but not ideal for algae prevention if for some reason algae takes hold on pool surfaces and does not circulate through the cell. I would like to see the SWG manufacturers consider using larger (longer) plate areas (probably in longer cells) so that the power per unit area can be cut down which should allow for lower CYA levels to be used. A doubling of plate area (and a lowering of voltage to keep the total current the same or a reduction in "on" time to keep the total FC production rate the same) should allow the cell to operate efficiently at 35-40 ppm CYA instead of 70-80 ppm CYA.

That's my two cents worth. I don't own an SWG system (yet) so can only comment on what others have said.

Richard

[nater]

What type of pool finish do you have?
Vinyl Inground

How old is your system?
System is 2 years old, has been in use for 10 months.

What Salt level do you maintain?
3000-3400

What are the benefits you're experienced from switching to salt?
No algae. Consistent Chlorine levels. Easy maintenance. Freeze protection feature is very handy this time of year as I don't "close" my pool.

What are the problems you've experienced since switching to salt?
No Pool issues. I have been going through cooling fans (bearing failures), but my unit is an older model. New fans are cheap at Radio Shack and easy to replace, just a minor annoyance I think that owners of newer systems don't experience.

How often do you have to clean your cell from calcium scale?
Never, even on the longest reverse time setting. I check it once a month.

How often do you test your water?
Every 2-3 days during swimming season, once a month during off season.

Thank you for your involvement on this forum Sean!

[Phillbo]

What type of pool finish do you have?
Inground Plaster

How old is your system?
9 months

What Salt level do you maintain?
3200 PPM

What are the benefits you're experienced from switching to salt?
lower maintenance ( just add acid every other week). Love the soft water feel and no need to wash chlorine off after a long swim.

What are the problems you've experienced since switching to salt?
None

How often do you have to clean your cell from calcium scale?
I check it every 3 months or so but have yet to need to clean it

How often do you test your water?
Weekly in the summer, Monthly in the winter

[tonyl]

What type of pool finish do you have?
Vinyl Inground

How old is your system?
Four years. Pool is open 6 months a year.

What Salt level do you maintain?
3300-3400

What are the benefits you're experienced from switching to salt?
Ease of maintenance. Consistant chlorine supply. Much easier on the skin, especially noted by my kids with skin dryness prior to switching.

What are the problems you've experienced since switching to salt?
None.

How often do you have to clean your cell from calcium scale?
Never, but I check it every 3 months. It's always been scale free.

How often do you test your water?
Weekly during the swim season

[waterbear]

Sean,

As you know from other posts on this forum, many (but not all) SWG users experience rising pH which requires regular additions of acid to maintain pH (and possibly adding baking soda to maintain TA over a longer period of time). Non-SWG users using BBB or liquid chlorine do not generally see the pH rise unless they have high TA, low pH, aeration from water features, or a new plaster pool (that is curing). waterbear (Evan) has found that using 50 ppm Borates significantly reduced this acid demand, possibly by reducing chlorine demand and allowing for lower power levels or run times of SWG generation.


Richard

Sean,
Richard is correct. Since adding the 50 ppm sodium tetraborate my acid use has decreased from about 24 oz every 2-3 week to about 6 oz evey 5 weeks and my pH tends to stay right around 7.6. I have also found that by lowering my adjusted TA to about 70 ppm has been beneficial. Since I have done that I have not seen my pH rise above about 7.9 while before it was not uncommen for it to read 8.2. I have also seen a huge decrease in chlorine demand since I can now run my cell at between 4-10% output depending on temperature (Goldline Aqualogic PS-8) to maintain my FC of 4-5 ppm while before I added the tetraborates I ran the cell at 15-25%! Also, my pool gets constant aeration from the spillover spa and water features (deck jets and spillover pots). I maintain my CYA at about 70 ppm and am located (as you know) in N. FL.
Evan