I'm getting some bids to build my pool and have a few questions about SWG's.
I've read all the negatives regarding the Nature2 units (the cooper it puts into the pool) but one builder is telling me that the nature2/SWG is a better unit (just don't use the mineral cartidge) than getting a stand alone Jandy SWG? Is there any truth to this? He's telling me it is actually cheaper as well compared to the stand alone?
Also, do I need to get a puck chlorinator (rainbow 320) to help out when the SWG doesn't work in the winter? Is there any problem getting the rainbow unit and only using it as a back up?

The nature2/SWG combo units tend to be undersized compared to other brands that claim support for the same size pool. Other than that they have about the same chance of problems as other units. My assumption is that the builder is pushing it because of their profit is higher on that unit, not because of what actually works better, but you never know.

There is no need for a puck feeder, but it can be handy to have one occasionally. They don't get in the way when you aren't using them.

Interjecting dumb question here... why wouldn't a SWG work in the winter?

I can see that maybe the filter won't run much in the winter but then you have to have circulation for the puck chlorinator as well.

Most SWGs will have an automatic shut off at a certain temperature. Mine shuts off at 50 degrees but I have found that algae doesn't grow when the water is that cold so I don't bother with adding chlorine. But then again, the water doesn't usually stay below 50 for more than a week or two and it is at a time of year when chlorine extinction is very low so there may be some carry over.

For the situation that I will be in. I will still need someway to sanitize the spa in the winter? How can I do that with a SWG that turns off?

I winterize my pool and use my attached hot tub all winter. I use chlorine during the winter. Normally, an SWG in that situation won't be your solution. Even running at 10%, it is made to chlorinate your pool and chlorine levels will be too high with the SWG running unless you turn it off/unplug it for the majority of the day. I find adding 1 cup of chlorine in my 600 gallon hot tub about 2-3 times per week to be a no-brainer.

You will need some chlorine when you decide to use the spa but I would assume that you turn on the heat when running the spa, correct? That will heat the water and the SWG will then turn on and you will get plenty of chlorine in the SPA while it heats. But your water may not ever get cold enough to shut off the SWG anyway.

Just remember your SWG is made for the entire volume of the pool and spa, so your chlorine levels may get WAY TOO HIGH if you use it full-time. As I said, it's much easier to disconnect the SWG during the winter and use small amounts of Clorox.

My SWG controller (and most others) have two modes, one for the pool and one for the spa so when in spa mode, the % setting is lower and won't add too much chlorine. With a spa, I would make sure any SWG that you are looking at has this capability.

Thanks for all the advice. I will have to see if my SWG will have a SPA only mode. Otherwise, I can just use the chlorine option.