Some numbers .. Hardness ?

[Phillbo]

Should I try to do anything about the hardness?

[chem geek]

Sorry, when I said that your water balance was near perfect, that means that your hardness (CH) is fine and you can leave it where it is. Also, I wouldn't worry about the alkalinity (TA) either. If you find that you have an upward pH drift over time and need to add acid regularly, then you can consider lowering your TA; otherwise, leave things as they are.

Richard

[mbar]

When you have a SWG, do you not have to keep the minimum chlorine the same as when you don't? The chlorine level of 3.6 is not high enough with a cya of 65 - 76. The minimum should be 5, max 10 and shock 20. THis could be why there is cc of .6

[chem geek]

Marie,

Well, this is a topic of hot debate as parts of this thread shows. Though the thread was mostly concerning the issue of why a higher CYA level is required for an SWCG system, the answers to that question also relate to why a lower chlorine level may be OK in such a system. Most people find that their CC remains at 0 in an SWCG system and I took a poll recently that showed that this is almost true with manual chlorination though some shocking (1-3 times per season) is typical. At least one user with SWCG reported having algae if not following Ben's table, but most found no problem using a lower amount.

So the jury is still out on this one though I'm leaning towards the belief that the continual shocking of a subset of the water plus fairly even continual chlorine dosing allows one to run at lower FC in an SWCG system.

Richard

[Phillbo]

Maybe I should play with the setting a little to see how much higher I have to set it to increase the chlorine to 5. It's a new system and I have been running it for 8 hours a day (overnight ) at about 30%.

I bought a much bigger cell than needed for my pool so I could run a lower setting . Is there a chart available that shows the increase achieved bases on extended run time or higher cell output ? I'll take a look at the manual when i get home but don't remember seeing anything.

[mbar]

Thanks Richard, I guess that's one good reason for looking at the water clarity. If your water doesn't have any problems, then the lower level is fine, on the other hand if the water isn't clear, then it might be better to raise the chlorine level to see if clears up, even if there is no cc.

[chem geek]

True, but you can't see bacteria! Fortunately, the amount of chlorine needed to kill algae is higher than the level to kill "easy-to-moderate" bugs (bacteria, viruses) up to and including E. coli. So if your pool water isn't developing algae, then it is more likely than not to be sanitized as well, but this obviously isn't a sure bet since you could just be "lucky" about having no algae (algae growth is dependent on other factors such as food sources including nitrates and phophates). At any rate, most users of SWCG systems seem to be operating below the minimums in Ben's chart (they are at around 3 ppm FC at up to 80 ppm CYA which is 0.015 HOCl level) and are still higher than that needed for disinfection (0.011 HOCl level roughly corresponding to 650 mV ORP) and since they are constantly generating chlorine to maintain their level, they are probably safe.

Nevertheless, I would prefer that the SWCG manufacturers design "longer" salt cells (more surface area so generation rates can be lowered per unit area) or change the internal flow rates and geometry so that they could operate efficiently using a lower CYA level (30 would be great, though even 50 would be much better). They will still generate high chlorine levels for their "shock" effect, but the lower rate per unit area will give the chlorine time to combine with the lower amount of CYA at normal flow rates (into and out of the cell, not inside the cell near the plates, where the flow is slowed down intentionally).

Richard