SWG and Ph balance

[DennyB65]

I have had an aqua rite system for about 6 months now. I know these systems tend to cause ph to drift upward. However, I have been adding 2 cups of acid every other day to keep it around 7.4. This seems like alot of acid to me. Has anyone else experienced this situation?

[waterbear]

What is the size and finish of your pool (plaster, vinyl, fiberglass?) and how new is it. These are all factors that need to be taken into consideration. The upward pH drift is normal becuase as the cell generates chlorine it also produces sodium hydroxide as a byproduct. If you pool is small and fiberglass or vinyl a pint of acid a day seems excessive but if it is a large, new plaster pool perhaps not.

[tonyl]

I've had the AquaRite for about 5 years now and the Ph will definitely rise and although you can't stop it, it seems to level out at about 7.8

Rather than fight it every other day, you might let it drift up a bit higher then knock it down to 7.2. For my 20K pool I'm adding acid (1/2 gal) once a week in the heat of the summer. I personally don't think it's critical to keep the ph low and steady as the FC within the cell itself is reportedly 100 ppm~ and my experience has been it sanitizes effectively even if the ph is a hair over.

So I've pretty much learned to relax and enjoy it. Check your water a couple times a week but don't panic to keep it 7.2-7.4, etc. In going on 5 years I've never had an algae outbreak and my water gets 90 in the summer. (My wife likes the heater~)

Hope this helps, Tony

[DennyB65]

My pool is diamond brite surface and is about 12k gal. It is 6 months old so i figured I would be past the period of high ph due to the new surface. Thanks for the info.

[mwsmith2]

The pH will continually rise, I think what you are observing is measurement error on the part of your pH test. The color changes aren't as distinct at higher pH levels. Higher pH usually leads to scale formation, and that's not good for the SWC cell. I generally dump 1 quart of acid in the pool weekly, and that keeps everything happy.

Michael

[kjsmom]

This begins my 3rd year maintaining our pool and I've done well (due to the Forum, thanks), but I'm STILL confused. We have an Aquarite SWG. Aquarite recommends a FC level of 1-3ppm. The first year, I maintained that FC level and had no problems whatsoever. Last year, I kept the FC level around 5ppm, (my CYA was around 30-50, which is below Aquarite's recommended 60-80ppm), and I had some trouble with the pH drifting up. So, my questions are:
1) Is a FC level of 1-3 ppm too low? (The liner mfg also recommends that level.)
2) Do high FC levels cause the pH to drift up?
3) I understand how CYA affects the "shock" FC level, but I don't understand what CYA has to do with maintenance FC levels, other than keeping the CL from disappearing too quickly. In other words, with a CYA of 30-50, why is a higher FC level required than if the CYA is 0?
4) Why does Aquarite recommend the higher CYA levels? According to the "Best Guess" cya chart, with a cya of 80 I'd have to maintain FC of around 8, which I'm afraid would be hard on my liner.
5) How can Aquarite recommend a cya level of 80, and a FC level of only 1-3ppm?
Thanks!
PAT

[mwsmith2]

There is no "trouble" with your pH drifting up (other than needing to keep it down) it's part of the normal operation of a SWC. The cell produces a small ammount of caustic as part of the electrolysis method of making chlorine. It's ALWAYS going to drift up.


The reason higher Cl is needed with higher CYA levels is because CYA inhibits the action of the Cl.

I don't know why they want 80 ppm CYA. I run mine at 40 with no problems.

Michael

[kjsmom]

Thanks Michael --
Needing to keep the pH down is just the trouble I'm talking about. So, if I maintained lower FC levels, the cell would produce less chlorine, and thus less "caustic", and the pH drifting up would be minimized???

Has anyone followed Aquarite's recommendation of 80 CYA and FC of 1-3ppm? I'd sure like to hear how that has worked out! I thought there used to be an Aquarite sales rep on the forum. Might he still be around?

Thanks again.

PAT

[Poolsean]

PAT,

I'm sure Aquarite's results are the same as AutoPilot's. Maintaining 80 ppm cya and 1-3 ppm chlorine is not a problem. It just does not react like a majority of poolforum pool owners that must maintain higher FC with higher cya.
Rest assured, I have a ga-zillion salt customers maintaining their pools with these parameters.

[mwsmith2]

Thanks Michael --
Needing to keep the pH down is just the trouble I'm talking about. So, if I maintained lower FC levels, the cell would produce less chlorine, and thus less "caustic", and the pH drifting up would be minimized???

Yes. But why? I run mine at 40% and drop 1 quart of acid in it a week. I'm not sure what the problem here is? Any time you add Cl in any form, you are going to affect the pH:


SWC increases pH
Bleach increases pH
Di-Chlor/Tri-Chlor decreases pHRunning your pool at lower Cl levels is a sure way to create a problem waiting to happen, either with algae or sanitation. Run 3 - 5 ppm Cl, dump in the acid for the pH and be happy!

Michael

[kjsmom]

Hi Michael --
It's not a "problem", I'm just trying to simplify my life! My, shall we say, "issues" are:

1) I have a new Pacific Pools liner; Pacific says to maintain FC at 1-3ppm. The old liner was temporarily patched last fall - 2 years old - and I was amazed at how much darker the patch was than the rest of the liner. Soooo, to help preserve the color of the new liner, I'd like to maintain the lowest FC possible, without compromising sanitation.

2) Aquarite recommends a FC level of 1-3ppm as "ideal".

3) My drop test kit shows a FC level of 1.0 as "ideal".

3) The first year we had the pool & the Aquarite, I actually did maintain FC at 1-3ppm and my pH was always perfect & I had no other problems. That may well have been dumb luck. The only thing I did differently last year was maintain higher FC levels because I was worried my water was not sanitary; my pH went up and I had to start adding stuff to bring it down.

If soda ash (sodium hydroxide) raises pH, and is a by-product of CL, then it would make sense that maintaining the lowest safe CL level would minimize the soda ash and thus the pH?? I guess the bottom line is, why is the higher CL level recommended here?

I appreciate your comments.
PAT

PAT

[mwsmith2]

The higher Cl level has been developed from heuristic methods by Ben. It's what "works" out in the field. Cl has been scientifically proven to be less effective at higher CYA levels. My other reason for keeping a higher that 1 Cl level is that it gives you some sanitation "reserve" in certain circumstances. I'd prefer to keep it at 3 and give myself some wiggle room, than to be bumping along the lower limit at 1.

However!

If it ain't broke, by all means, don't fix it!

Michael

[kjsmom]

Thanks Sean, You are the sales rep I remember from the old forum -- sorry I got your company mixed up.

I think I'll try actually adhering to Aquarite's recommendations this year and see what happens!
PAT

[waterbear]

Thanks Michael --
Needing to keep the pH down is just the trouble I'm talking about. So, if I maintained lower FC levels, the cell would produce less chlorine, and thus less "caustic", and the pH drifting up would be minimized???

Has anyone followed Aquarite's recommendation of 80 CYA and FC of 1-3ppm? I'd sure like to hear how that has worked out! I thought there used to be an Aquarite sales rep on the forum. Might he still be around?

Thanks again.

PAT I have the Aqualogic ps-8 (same salt cell as aquarite) and I keep my CYA at around 80 (it's a bit low right now at 55 but I am gonna wait until it goes close to 40 OR my builder fixes the leak in my skimmer before I bring it back up) and I keep my FC in my pool at 3 ppm and in my spa at about 4-5 ppm and I have had no problems so far.
Also, I wonder if the fact that the water in the cell is constantly being 'shocked' when the cell is operating vs. manually adding chlorine and shocking might cause a difference in how the pool reacts to the CYA and FC levels. That would be an intersting piece of research!

[kjsmom]

Also, I wonder if the fact that the water in the cell is constantly being 'shocked' when the cell is operating vs. manually adding chlorine and shocking might cause a difference in how the pool reacts to the CYA and FC levels. That would be an intersting piece of research!

I agree; there was talk on the "old" forum about the steadier flow of cl keeping the water chemistry more stable. Thanks.
PAT

[mwsmith2]

Also, I wonder if the fact that the water in the cell is constantly being 'shocked' when the cell is operating vs. manually adding chlorine and shocking might cause a difference in how the pool reacts to the CYA and FC levels. That would be an intersting piece of research!

Already been done. :D The answer is yes. Prior to installing my SWC, I used bleach and always had about 0.5 CC. After installing the SWC, my CC dropped to 0 and has been there ever since. Sean has also mentioned in the past that the concentration of Cl is high enough that it does act like a continual "shocking" process. I can definitely confirm the results, as I have not had to shock the pool since I installed the SWC.

Michael