PS234s results (trying to run high pH)

[CAL7]

I am a few days into converting to an AutoPilot Dig220/SC-60, so I expect to see the Cl levels fluctuate as I adjust the unit. But, here is what I have now:

Pool: Inground gunite (4 mo old DiamondBrite finish), 34K gals., propane spa heater, Autopilot SWG
FC 6.0
CC 0
TC 6.0
pH 8.2 (Maybe more - see below)
Alk 130
Cal 350 (normally this would be within range, but above "high pH" recommendations - link below)
Cya 58 (interpolated between 50 & 60)
Salt 3300ppm (per Autopilot; PS234s tip causes drops which are too small for a valid test)
Temp 81F

Before the SWG, I was pouring in Muratic Acid at a rate of (about) a quart a day; despite some contrary reports here, I expect to see the acid demand go up even more with the SWG. This had me researching high pH pools, ref: http://www.poolsolutions.com/gd/hiphpool.html. Following the recipe and satisfying all Ben's "ifs", I decided to give it a try. Note that the Calcium at 350 is higher than required level of 300 specified in the link, but the levels have been coming down since the new finish was applied, so I am hopeful Cal will get to 300 in time.

First Question: Anybody see issues with what I am trying to do?

2nd Question: I was expecting the PS234s kit to give me an improved pH test over what I had (PS200 equivalent), but the only pH test is the PS200. So, I am unable to test pH levels over 8.2. For all I know, my pH is way above 8.2. Diluting with distilled water did not seem to work to test for high pH. How can I get an accurate reading of pH above 8.2?

Thanks for any advice.

[waterbear]

How can I get an accurate reading of pH above 8.2?

Thanks for any advice.

You need to use a different indicator than phenol red which will only test pH in the range of 6.8 to 8.2.

[CAL7]

You need to use a different indicator than phenol red which will only test pH in the range of 6.8 to 8.2.

Do I need to get base-demand and acid-demand reagents to do this? Do I need a complete kit, or can I go to the pool store and just look for Taylor reagent refills to accomplish what I want?

Also, if I can assure I am actually at 8.2, are there any comments about running my pool this way on a permanent basis?

[cwstnsko]

Just my thoughts, not an authority.

According to my calculations, your water right now has a saturation index of 0.70 This number will go even higher if as the temperature increases. Ideallly you want this to be below 0.30 At 0.70, I would expect you will get calcium scale at the waterline, and quite a bit of scaling in the SC-60 cell. To keep the cell from getting overly scaled between voltage reversals, I would reduce the time between voltage reversals to something less than the standard 4 hours, this will shorten cell life, but it will keep the cell from becoming excessivly scaled. I'd try 2 hours and watch for build-up in the cell. You will probably get little white flakes of calcium in the pool each time the cell reverses and sheds the build-up.

If you want to run the PH that high, you'll have a lot better water balance if you can get the Alk down to about 80 and the Calcium down to 200 or less. It'll be a lot easier to manage at those numbers.

The alk can be dropped with acid and aeration, but the Calcium will need to be reduced through a water change or some sort of softener setup.

Have you tested your make-up water? The nature of your make-up water may factor into the plan as well.

[PatL34]

If you try to run the SWC at pH levels above 7.8, there will be next to no chlorine production. Ben's method will only work with bleach, and you sort of need to do a paradigm shift when converting to a SWC.

Best Cl production will be between 7.2 - 7.6 pH.

This will also help to keep your CH under control as you are probably still curing, even after 3 months. As cwstnsko said, you will need frequent water changes, to bring the CH down, and I would not go >200 ppm.

Your TA at 130 ppm is not too high, but I would start doing some dearation if goes higher. Again a lower pH will help to keep this in check as well.

Hope this helps.

Pat

[waterbear]

another thing to condsider is that the amount of hypochlorus acid in the water is going to be minimal and most of your chlorine will be in the form of hypochlorite ions at that high a pH. Hypochlorus acid is what actually is a sanitizer, hypochlorite ions are not.

SWGs are different because they are producing sodium hydroxide (lye) when they generate chlorine which is what causes the pH rise. Running a high pH pool is more of finding where a plaster pool wants to go and not fighting it all the time when sanitized by manual chlorine addition.

To test pH that high you need a different indicator and test block or a pH meter. That pH range is not normal for pool/spa use so you will have to look outside of the pool test kits to find it.Taylor and LaMotte probably have some kits that will test that pH range (I bellive that some of LaMotte's soil testing labs do) but be aware that you are getting into 'experimental waters' so to speak.

The Hamilton Index is what is ususally used to run a pool at a higher pH and that does not use Calcium hardness but rather total (calcium and magnesium) hardness in the equation. Temperature becomes much more important in this equation also and it is accepted that the sanitizing abilities of the chlorine are lessened too.

The Hamilton index is probably about as useful as the Langelier and Ryzner indecies for balancing a pool which, IMHO, are not really usefull tools. (But that is a different and somewhat technical discussion that is probably best in the China Shop!)