Looking for Advice - Possible SWG Convert

[SteveK2]

Tony, thanks for the response. It is appreciated.

They way I was looking at things, in a pool without SWG, there is no correlation between chlorination and filter run times. But with an SWG, there must be, since the SWG will be generating chlorine ONLY if there is water flow (isn't that the function of the flow switch -- to ensure that water is flowing through the system otherwise gases may build up in the SWG cell?)

I don't get the significance of the 100 minute cycle you mentioned. (Just me perhaps). BTW, I think the last part of your example (minutes 200-240), there will only be 20 minutes (50% of 40 minutes) of SWG "on-time". Bottomline is this -- if the SWG is set to 50%, then it will only be "on" 50% of the time that water is flowing (filtering) in the system. In doing some more reading on SWGs (the Aquarite in particular), its spec sheet says it will generate up to 1.45 pounds of chlorine per day. That would be @24hours filtering/pumping time. At 8 hours per day (my schedule), one-third of that amount of chlorine would be produced if I set the switch @100%. So the question is -- will 0.48 pounds of generated chlorine be enough to sanitize the pool?

Using the bleach calculator from this site MIGHT be useful in answering this question. So, using bleachcalc, I plugged-in my relevant numbers: 30,000 gallon pool, 6 PPM desired PPM target, 100% bleach strength for generated chlorine (would this be correct?). The result says I need to add 2 cups, 7 ounces to the pool. I don't know how to equate liquid chlorine volume with generated chlorine's "weight".

Am I making a valid comparison here?

Maybe someone who is familiar with that calculator can tell me if

[tonyl]

I didn't explain myself very well with the 100 minute cycle example. It operates as if there will always be 100 minutes to work with. In the last example of 200-240, there will only be 40 minutes of generation because although the generator is set at 50%, it won't know the timer will turn the pump off at the 240 minute mark. It "thinks" there will be a 200-300 minute cycle.

Chlorine demand varies greatly depending on a variety of factors like bather load, number of kids, etc. I have a wife and two young girls and my pump runs 8 hours a day at about 25% setting in the summer and free chlorine level at 2~ and our pool gets full sun. I also keep the salt level at the max. recommended level of 3400 which helps me lower the output setting for efficiency and cell life. CYA gets bumped up to 70-80 as well which also helps the chlorine stick around. So again, there's a few things that have to be considered relative to how much chlorine your pool will need.

Hope this helps, Tony

[chem geek]

1 pound of chlorine gas is equivalent to 15.3 cups of 12.5% (trade) chlorinating liquid or 31.1 cups of 6% (weight; 5.7% available chlorine) bleach.

I doubt that you are adding 6 ppm FC every day -- that is your target number, not your usage number. Your usage may be about half that, or 3 ppm FC. For your 30,000 gallon pool, that would require about 23.3 cups of 6% bleach which is the same as 12 ounces of chlorine gas. That's 12/(16*1.45) = 52% on-time assuming their numbers are correct and that your true FC requirement is 3 ppm per day.

Richard

[SteveK2]

Tony,
OK, thanks. Now I get the 100 minute cycle significance. And thanks for describing your pool environment - it helps quite a bit and is similar to my environment. Can you just let me know the gallonage of your pool? That would help me make a better comparison of the overall environment.

Richard,
Thanks for the info comparing generated chlorine to the liquids. Yes, you are probably right that my chlorine consumption is no where near 6PPM per day. I can't say I know my 'typical' daily consumption, because I haven't really tried to track that. So if I really need to replenish 3PPM every day, then a 52% "on-time" is between12 and 13 hours of filter/pump time with the output set at 100%.

Thanks again to both of you!

[chem geek]

You know, if pump time is the main concern there are a couple of solutions for that. First is to get a more powerful SWG -- even get a second one if you don't want to replace the first with a larger unit. Your 30,000 pool size is on the large size so is why a typical SWG unit has to be on so much. With more SWG power, you can run your pump a shorter period of time.

Another alternative to keep pump costs down is to use a variable speed pump and run at a slower speed. That way, you can have your long run time, but not use as much electricity while still getting the minimum single turnover per day that you need.

Richard

[tonyl]

Steve,
Glad I can help. My pool is right at 20k gallons. (18X36 sport pool, 5.5' in the middle and 3.5' on each end) Anything else I can help you with let me know.
Tony

[SteveK2]

Richard,
Good suggestions and very much appreciated. Although it probably doesn't seem to be the case, filter run time isn't that big of a concern. I am just trying to understand what to expect. My main goal is convenience and not cost savings, but I want to know up front if my costs (like filter run time) will go up.
Thanks again. The info from you and all others will help make a decision (which I expect to make very shortly).

[SteveK2]

Thanks to everyone who provided information on this topic. I have placed an order for an Aquarite SWG. Looking forward to installation followed by relaxation and a summer of enjoyment!
:-)

[PatL34]

Thought I would add my two cents on this particular topic, and also raise a few eyebrows at the same time.

I have been out of the Pool Forum loop since September 2006, owing to medical problems and other things.

As I maintain the pool, it obviously has not received the TLC that many members normally give to their pools.

Why is that? I could have had a pool supply service the pool, but why waste money when I know I can do the job better.

I have not added the muriatic acid on a regular basis like I should have, so I was waiting for the algae to show up eventually. Remember we were in winter at the time in Central Florida. Water analyses have been done, but only when I was in the mood.

Now many of you are thinking that I don't give a damn. But I do. I had to have the pool relined with Diamond Brite, because the original plasterer added sand to the mix to make it cheaper.

The plasterer who finally did the job correctly, has given me a pool that can withstand more abuse than any pool that I have come across.

I am now adding acid on a regular basis, and finding that the pH is the only thing I have to control.

I have not checked the cell in all this time, but feel I may have to one of these days.

The point I am trying to get at, is that SWCGs require a lot less maintenance then people realize.

I have had a SWCG since 1998, which was part of a package including solar panels. I upgraded to a PoolPilot 3 years ago, and have never looked back.

So with apologies to CarlD, SWCGs save an awful lot of trips to the pool store, requiring the use of gasoline, hefting cans of liquid chlorine.

I did a cost analysis of what it would cost to run a SWCG, (ignoring the initial purchase cost of the unit), in this forum a year or more ago. Compare that to what you have to pay in liquid chlorine cans and gasoline, for the same effect as a SWCG.

Pat

[nater]

Welcome back Pat, its good to see your thoughts in the forum again! Best wishes with your health, I hope you'll be able to fully enjoy your new plaster this year