So how come there aren't a LOT of sick people?

[Tredge]

It's not that SWGs are "different", it's that when running properly they have two advantages over other chlorination systems:
1) They are constantly gen'ing chlorine at low levels. You don't actually need a lot of chlorine to keep your pool sanitary, but it has to be able to respond to demands on it--like people and suntan oils, etc. A residual level gives you a safe lee-way or metabolizing stuff will drop you below that sanitary level, leaving your water vulnerable to contamination. But an SWG takes over for that
2) They super-chlorinate the water that passes through them, killing everything in it.

Remember: SWGs ARE chlorine systems and follow chlorination rules. But rules of thumb may not be as applicable.

I've read the threads and the very informative PDF link on CYA....I'm trying to understand.

If SWG's constantly generate new chlorine then there should be less need for CYA not more!

They way I understand it CYA acts as a time release but the tradeoff is that the chlorine isnt as "active". I understand the value of that tradeoff if I were adding chlorine once a day but a SWG adds all day and night.

I also understand that a SWG superchlorinates at the cell and in the pipes...but high CYA has nothing to do with chlorine in the pipes, its intended for keeping chlorine in the pool longer (Protection from sunlight esp)

I'm sure SWG's opperate safely at these CYA levels...I guess I just cant get my mind around the science behind it.

[aquarium]

The part of that PDF article that got my interest is this chart:



He suggests that 5-12ppm is good for an automated pool, no more than 20ppm for a manually managed pool.

[PatL34]

If SWG's constantly generate new chlorine then there should be less need for CYA not more!

Actually you need more! The cell instantaneously generates a high concentration of chlorine that destroys the chloramines AT the cell.

If there was not a high CYA level, most of it would be used up before it got into the pool proper. The alternative would be to run at high chlorinating outputs, resulting in rapid reduction of cell life.

Hope this helps.

Pat

[Rangeball]

Tredge, I don't get the feel that SWG owners are operating their units 24/7, and as such need the CYA to keep the residual when the unit's off.

[Tredge]

My SWG manufacturer recommends 24/7 but they could be unique.

I'm just hearing conflicting things and the technical evidence in this thread supports a lower CYA....especially for SWG systems.

I understand a high CYA can extend the Cell life because you can maintain a lower chlorine ppm at a lower setting, but does that really mean a healthier pool?

Would it be incorrect to say that a SWG system running at 0 CYA and 1ppm chlorine 24/7 is the most effective? (Not taking cell life into account).

I dont want to contradict this forum, perhaps a new thread in the "china shop" is more appropriate?

[aquarium]

If you run a SWG 24/7 does that mean the main pool pump is also running 24/7?

[Tredge]

If you run a SWG 24/7 does that mean the main pool pump is also running 24/7?

No it runs on its own or with the filter running. It has its own pump that is capable of pulling water through the filter.....although not nearly as fast of course.

[PatL34]

My SWG manufacturer recommends 24/7 but they could be unique.

I'm just hearing conflicting things and the technical evidence in this thread supports a lower CYA....especially for SWG systems.

I understand a high CYA can extend the Cell life because you can maintain a lower chlorine ppm at a lower setting, but does that really mean a healthier pool?

You use whatever setting YOUR pool needs to be healthy. It will depend on bather load, weather, and any other kind of upsets. The lower the setting you can use on the pool the better.

Would it be incorrect to say that a SWG system running at 0 CYA and 1ppm chlorine 24/7 is the most effective? (Not taking cell life into account).

Yes it would be incorrect. Please reread what I said in my post above. You need the CYA ppm for the reasons stated.

I dont want to contradict this forum, perhaps a new thread in the "china shop" is more appropriate?

Hope this helps.

Pat

[bbb]

Actually you need more! The cell instantaneously generates a high concentration of chlorine that destroys the chloramines AT the cell.

If there was not a high CYA level, most of it would be used up before it got into the pool proper. The alternative would be to run at high chlorinating outputs, resulting in rapid reduction of cell life.

Hope this helps.

Pat

:lightbulb lighting over head:

Thanks, Pat. This is about the 10th time I read that if there was not a high CYA level, most of the SWG-produced chlorine in the cell would be used up before it got into the pool proper - and I finally figured it out -

Without the added CYA, the superchlorination at the cell is TOO effective, so, under higher bather load or organic contaminant conditions, there isn't much unused FC left after the water passes the cell and goes toward your return!

With additional CYA present (say 60-80 ppm), there is a little less superchlorination at the cell (because chlorine is less effective per PPM with CYA present), so there is more residual left as the chlorine passes back into the water into your pool, where it can fight contamination of the water actually in the pool and (keeping this sort of on topic), preventing people from getting sick from stuff in the pool!

Finally, because there is still effective (just a little less powerful per PPM because of the 60-80 ppm CYA) superchlorination going on in your water because the salt water generator cell is operating, you should be able to run with a (slightly) lower amount of FC residual in your SWG pool than with a pool chlorinated in batch form (like bleach or cal-hypo) or drip form (chlorine feeders, trichlor pucks) for your given level of CYA.



ps - the "benefactor or bomb" article is very good but needs to be taken with a grain of salt (whether or not you are running a SWG! ) PoolDoc has excellent comments elsewhere on the forum about it - here is the link. CYA is NOT "bad" -- running your pool with too much of it and not enough chlorine (like anyone using a constant amount of trichlor pucks in a feeder all year, and using a test kit or strip that only counts to 5 or 10ppm of chlorine) IS "bad". It's that simple. And for people who have very sunny pools (aylad comes to mind), CYA is a huge help. My pool isn't that sunny, but when I cholorinated exclusively with bleach last year, I chose a higher CYA rate so I could add bleach every other day instead of every day. And now that I have an SWG, I am slowly increasing my CYA from 35 to (probably) around 60.

My understanding: with the addition of common sense and real-world experience to the "benefactor or bomb" material, you get Ben's "Best Guess" chart.

[Tredge]

PoolDoc has excellent comments elsewhere on the forum about it - here is the link.

Thanks for linking that. Ben does an excellent job as usual responding to that article.

The folks in this forum are really impressive.