SWG hot tub...what chemical levels should I be at?

[ndakotaninja]

So I know I can't be the only person with the same set up, so hopefully someone can chime in with how they do things. I have an in-ground pool with an in-ground spa. They both use the same equipment (pump, filter, heater, SWG), but you can turn the valves to draw in only pool water, only spa water, or some from both, and then output to either the pool, the spa, or once again, both. There's also a pipe underwater connecting the 2 together that I can leave open to make sure the water balances out, i.e. if someone sets it to draw from the spa and output to the pool, water can flow back into the spa from the pool if the water gets too low so you don't blow your pump motor out. I also have a cover for the hot tub that normally stays on to protect it from the sun/keep it clean/keep it warm. Unless I'm planning on using the hot tub and want to keep it warm overnight so it takes less to heat back up the next day, I have been leaving the pipe open to allow water/chemicals/etc to flow and keep everything sanitized.

So I have 2 questions. I've seen the recommended chemical levels for hot tubs and they're different from the recommended levels for my pool. So is it a problem that, because the 2 are connected and all the water is essentially the same, my spa chemical levels are not ideal for a spa setting? It seems that the chlorine levels should be about the same, but if I have several people in the spa using it, would I still have to shock it and worry about getting the chlorine level back up, or should it act the same as if I had several people in the pool (I assume 4 people swimming in a pool would do relatively little in terms of the chlorine levels and shouldn't need shock...so same for my hot tub?). Secondly, because it has a cover, hot tubs CYA should be around 30ppm, but my pool should have around 70. Again, is this a concern, or does it really matter?

Second part is related to the fact that I use a SWG to produce my chlorine. I run my SWG at a fairly high % to keep up with demands in the pool. However, I've noticed that when I shut off the pool intake/outtakes and just use the spa, the water starts to get a whitish color from all the chlorine that's getting pumped into it. I can turn it down or shut it off while I'm using the hot tub, however I could forget to turn it back up/on afterwards and cause other problems with the pool like algae. So the question is, should I bother adjusting the SWG when I use the hot tub? I don't like the way it looks, but as long as it won't hurt anything or get too high, I guess it's safe still. Or is it recommended to turn it down/off while using the hot tub?

 

[JasonLion]

When a pool and spa share plumbing you maintain the combination at swimming pool levels, and setup the circulation system so the two bodies of water are mixed together at least once every 24 hours.

You don't want the SWG on at pool levels of production when in spa mode. When in spa mode, you should either turn off the SWG, or turn it down to about 1/10th of the percentage setting you would otherwise be using.

 

[ndakotaninja]

That's good information to have. I'll have to make sure I train my significant other to also turn the SWG off/on if she switches the system to spa mode and back.

Should I get in the practice of testing the chlorine/pH of both sets of water each day as well? Or will that not matter so much as long as both are clean and I run it in combination together to mix them up on a regular basis (I'm sure when I'm swimming every day like I plan I'll combine them daily, but for now it's about every 2-3 days I run them together for the day, then turn it back to pool only.

 

[JasonLion]

Normally, you only need to test the pool. As long as the pool and spa are getting mixed together daily it is effectively one body of water. If you mix less often, there could be issues in the spa.

 

[chem geek]

Also, you should try and mix the water between the spa and pool soon after you get out of the spa. Depending on your bather load in the spa, the chlorine could get used up and allow bacteria to grow so you don't want to wait many hours before either mixing with the pool or adding chlorine to the spa when you get out.

If you have 3 ppm FC with your 70 ppm CYA in the pool, then starting with that level in a hot spa should handle up to 25 person-minutes of soaking in a 350 gallon spa. If you test your chlorine level in the spa about an hour after you get out and if it's near zero, then you should either add chlorine to the spa manually (say, adding bleach or chlorinating liquid) or mix the water with the pool within an hour or two of getting out of the spa.