Best method to "dial in" the SWG?

[joshs2000ss]

I've been working for a week and a half on my first ever pool opening. New house, came with a pool. Using the methods described on this forum, my water chemistry is dialed in. Now I need to dial in the SWG. I realize that the usage, spill out and varying temperatures throughout the year will affect the demands on the SWG and my settings, but what is the best way to go about getting the output where it needs to be?

I'm assuming the goal is to minimize pump run time while keeping the SWG output set at the proper level to compensate for FC loss. I'm just looking for the best/proven method to do so.

 

[benavidescj]

Start with a reasonable run time like say 8 hours per day. Enough run time to keep the water filtered well. Then set the SWG to where it gets you enough chorine to compensate for loss. Then monitor the chlorine. If the chlorine tends to drop, bump the time on the pump up a bit. If it tends to go up, bump the run time down a bit. I also tend to bump the percentage on my SWG up or down when the drift is real slow, keeps me from having to adjust the pump run time a lot. After I get the chlorine to shoot past were I need it for a day or two I bring the percentage back to where it was.

 

[JasonLion]

Pump run time should be optimized to get enough filtering done to keep the water clear, while the SWG percentage should be optimized to produce enough chlorine to maintain the correct FC level. Sometimes those two things interact, when the ideal filtering run time is so short that the SWG would have to be higher than 100% to keep up, but for the most part they are completely separate from each other.

There are articles in Pool School covering both of these topics separately, though there isn't much on how they interact.

 

[joshs2000ss]

According to the pump specs and some speculation on the pump "head in feet" numbers, at almost the very least, my pump can turn the pool water "over" in 5 hours. So I'm thinking I could, at the very least, leave the pump off over night and then turn it on before I leave for work and turn it back off when I get home (~11 hours). I guess for the first few days, I can do this and test the FC levels to see where they are with my SWG on maybe 60% (outside temps are supposed to warm up)? I say that because with my generator running for 12 hours through the day today (cold day) at 50% my FC level climbed from 3.5 to 4. So with an hour less run time, it will be closer to maintaining the level and I can adjust accordingly from there.

With that said, is it better to turn the pump off at night and run it in the day, or vice versa, or does it matter?

 

[JasonLion]

If you have time of day electric rates, you should run the pump when the rates are less expensive. If your timer can handle it, it is better to split the run time up into two or more segments spread across the day. If you run out of other reasons, running the pump during the day is a little bit better.

If your levels are properly balanced, especially CYA, you shouldn't need to run the pump any where near that long for the SWG to be just fine.

 

[joshs2000ss]

I'll experiment some and see what I can come up with for a few days. I don't have a timer, so this is all manual. Hope to invest in one sometime in the future though.

Currently we don't have time of day electric rates, but we are going that direction soon. I'm sure that will play a part in my pump running plan when that time comes.

Currently my numbers are looking pretty good. CYA is 70, FC is 4 and CC is 0. I will probably run another full set of tests in the next day or two to make sure everything is holding where I want it. The water temp is pretty cold right now (63 degrees)and I'm sure when the water warms, with the sun and with the heater when I turn it on, I'll have to revisit some of this to get everything setup with those factors in place.

 

[dmtreff]

I might add that you should monitor your daytime chlorine levels carefully if you run the pump (and SWCG of course) at night. This means that your pool is not getting any chlorine production during the day when the sun is bearing down on it. That is the time when you need chlorine to be replenished. The double whammy here is that if you allow your chlorine levels to drop below recommended during the day, you are going to make a more hospitable environment for algae, and nobody wants that... especially when the sun is shining. Algae LOVES the sun.

When I first got my SWCG, I tried running it at night but was unhappy with the fluctuation of chlorine levels by the end of the day and I had a slight algae problem. Since I switched to daytime running, my chlorine levels stay steady through the day, and of course don't budge at all at night when there is no sun. No more green stuff. Of course that failed experiment was before I found TFP and learned more about pool chemistry. Maybe now that I have my water properly balanced and treated with the right dose of stabilizer, I could give it another go without the chlorine levels fluctuating so much.

I guess it's a trade-off. If you can find a compromise whereby you get some cheaper electric rates at night without compromising your water quality, go for it.

Just my $0.02

 

[JasonLion]

I might add that you should monitor your daytime chlorine levels carefully if you run the pump (and SWCG of course) at night. This means that your pool is not getting any chlorine production during the day when the sun is bearing down on it. That is the time when you need chlorine to be replenished. The double whammy here is that if you allow your chlorine levels to drop below recommended during the day, you are going to make a more hospitable environment for algae, and nobody wants that... especially when the sun is shining. Algae LOVES the sun.

This is almost completely a non-issue. There are some small advantages to running a SWG during the day, but running at night works perfectly well and is recommended if you have time of day electricity rates. All you need to do is to adjust the SWG % setting as recommended in Pool School (so the early evening FC level is appropriate) and everything will work just fine.