pH rise with SWCG?

[JamesR]

A few weeks ago I installed a Circupool RJ60+. Then I went on vacation for 16 days. While away I had my daughter check salt levels and chlorine levels every other day and adjust as needed. She had to add one 40 pound bag of salt. And twice she added a gallon of chlorine.
My CYA is at 60. I had her try to keep the chlorine at about 6–8 ppm while I was gone just to be safe. She did that.
Now that I’m back home I did a full analysis. pH spiked up to 8.2. Is this expected with a SWCG? My pH was always very stable at about 7.5 prior. Another odd result was that my CH dropped from 350ppm to 250ppn.
What’s the explanation for that? She added no water to the pool. Between the normal evaporation and the rain, the water level remained fine.

 

[needsajet]

How were you doing chlorine before the SWCG?

 

[JamesR]

I was adding liquid chlorine. Using the 12.5% jugs from Ocean State Job Lot.
In the summer it was probably 4-5 gallons a week. Just not practical. So I installed a Hayward VSP and Circupool SWCG.

 

[RookiePick]

Why did you have her checking salt every second day?

 

[JamesR]

Because this was a new setup for me. Never had a SWCG before. I was out of the country for over 2 weeks and did not want to come home to a swamp. I had zero data on salt usage or stability. So I figured it was best to track it often.

 

[RookiePick]

You will only lose salt to splash out plus top up and dilution from rain + pumping out water.

It is one of the more awkward tests with less friendly reagents so I wouldn't sweat it too much. Once a month should be fine I think unless you have a big water exchange event.

Can't hurt though, just expensive testing.

 

[JamesR]

So what’s the theory on the rise in pH and the drop in CH?

 

[Newdude]

Everybody needs to reach their comfort level of things not changing, in order to extend the testing intervals. Do not micro manage the salt. The test has a wide variance for error and you cab get into trouble adding salt frequently. Once the cell is working, only step in at the low threshold when the cell complains. Verify, of course, first.

Over time you'll see the salt is as stable as the CH. CYA burns off a little, but the other 2 only dilute. For both of them to drop considerably, water was added if the testing wasn't done in error.

pH spiked up to 8.2. Is this expected with a SWCG?

Did you increase your pump run time due to the SWG ? Usually the extra aeration which ensues causes said PH rise. Many blame the SWG, but it's really the pump. You can lower your returns a little to help either way.

 

[JamesR]

Yes…. I run the new pump 24/7 now as opposed to 10 hours a day.

 

[mgtfp]

Lower TA will help to reduce the pH rise. Lower TA means less carbonates in the water and therefore less CO2 outgassing.

Lower TA would also help to reduce your CSI a bit. With a SWG you want that slightly negative (-0.3 to 0) to reduce scaling on the SWG cell plates.

 

[setsailsoon]

A few weeks ago I installed a Circupool RJ60+. Then I went on vacation for 16 days. While away I had my daughter check salt levels and chlorine levels every other day and adjust as needed. She had to add one 40 pound bag of salt. And twice she added a gallon of chlorine.
My CYA is at 60. I had her try to keep the chlorine at about 6–8 ppm while I was gone just to be safe. She did that.
Now that I’m back home I did a full analysis. pH spiked up to 8.2. Is this expected with a SWCG? My pH was always very stable at about 7.5 prior. Another odd result was that my CH dropped from 350ppm to 250ppn.
What’s the explanation for that? She added no water to the pool. Between the normal evaporation and the rain, the water level remained fine.

James,

At 10 hrs per day you were only adding 1.7 ppm FC per day. Too low for this time of year even up north. 3 ppm or even higher is more likely required. At 24 hrs per day you are 4 ppm which is in range for this time of year... watch it and tweak a little lower with either reduced run time or lower %. Don't chase this or you'll go nuts. Let it cycle in a range with the highest number always being the high target or a little higher. Use Pool Math to estimate settings, it's very helpful. If FC gets too low as you tweak continue to adjust quickly with liquid... this shouldn't take long at all. I always got mine cycling in the proper range in just a few days. If you ever see it drop unexpectedly low do an OCLT test to be sure you don't have the beginnings of an algae issue. After a month or two when you're in town you'll get to know the pool with the SWG and you'll be on easy street.

As to the salt level, it only changes by water addition or removal from the pool. So you must have had some big rains and that explains a lot of the variations. I would also recommend you get the K-1766 test kit and do not rely on salt readings from the cell. Sooner or later they will become unreliable. Sometimes you will notice pH rise right after adding liquid bleach but the net effect is zero change as it reacts to sanitize your pool. With SWG the FC is added so slowly and continuously you won't see the change. If your pH is rising that's normal and due to aeration. You will need to add acid for this and lowering your TA to as low as 50 will help stabilize the additions. I ran this way for years and it was much improved. If it doesn't stabilize consider adding borates. I would try lower TA for at least a while since borates are just another chemical to monitor. You'll find a lot of subjective benefits about borates documented. I didn't see any of them. They only stabilized my pH.

I hope this helps.

Chris

 

[drsipe]

My PH tends to creep up when my TA is too high. I have found that a TA of 60-70 greatly slows my PH creep.

I would use muriatic acid to lower your PH to 7.2 -7.5, this will also lower your TA. You can experiment at what TA level your PH creep slows/stops, just keep the TA above 50.

Your CSI is a little high, and you may start to experience calcium building up on the plates of your SWG. You can play with pool math to determine what you need to do to get a negative CSI. My CSI is usually around -.2 to -.3, and I have no build up of calcium on my SWG.

I can't give you a logical explanation of why your CH has dropped, the usual explanations are drain/fill with lower CH water. I don't think if you have calcium build up in your SWG, it would be enough to effect your water chemistry, but with a positive CSI I guess it could be possible.

 

[setsailsoon]

I certainly agree on the csi. Ran mine slightly negative at all times... Pool Math is a great tool to figure out easiest way to reduce the TA.

 

[needsajet]

You'll likely eventually settle with accepting pH around 7.8 as fine.

It works and minimizes the frequency of adding acid. I wait to see 8.0 and then correct to 7.8. It's been around a cup a week for as long as I can remember.

Does your pool have a water feature at all?

I'd be looking to get the pump run time down, but my bias is because electricity is expensive here compared to there, so perhaps that's not a big deal.

 

[JamesR]

No auto fill for the water.
Electric rates aren’t too bad right now. We are allowed to shop for electric suppliers here in PA. I am paying about 9.6 cents /KwH. With distribution charges it comes to about 14 cents /kwh.

 

[needsajet]

Yeh that's very good electrical cost. No, I was wondering about if you have a water feature such as a waterfall or bubblers or fountain kinda things, not autofill

 

[JamesR]

No bubblers or fountains. No aeration of any sort except for when the spa is running. But that has not been used in this heat wave.

 

[ajw22]

The aeration from the hydrogen bubbles the SWG creates does seem to cause more pH rise. Keeping your TA around 60 seems to limit that. Just lower the pH when it gets above 8.

The higher the SWG %, the more the SWG generates, and the faster you see the pH rise. So as you get into the summer and increase the % you see it more. As you decrease the % in the fall you will see it less.

 

[JamesR]

There is a steady flow of H2 bubbles when it’s running. So that could be the culprit.
I’ll keep dropping the pH. That should slowly lower the TA. I’m at 90 TA now.

 

[mknauss]

Does the spillover spa now run 24 hours per day?