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The important factor is that at higher pH the chlorine needs to be higher...

Following Jock's treatment plan there is no longer a need to super chlorinate...

I have used UC products since 1984 and have found nothing but success...

Bill Tech II

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Bill Tech II

So what happens to the chloramines then? Do they not form at a pH of 7.8 and higher?

Bill there is nothing wrong with UC's chemicals, but I do not like (never have) Jock's idea of keeping the pH at 7.8 - 8.2 and never below 7.6. Water at pH 7.2 - 7.6 always looks better and everything works better than when the pH is higher.

Okay Ross, I'm ready to take you up on your offer to help me balance my water. I've done a little balancing myself this week and took a sample into Leslies tonight for a workup. Unfortunately I failed to ask them to measure TH (total hardness?) so I'm not able to give you complete information. Here's what I can tell you:

I ran the salt system for 24 hours 2 nights ago to shock the system. As of today the (free) chlorine level is down to 5 ppm. I haven't yet backwashed the system but figure this would be a good thing to do to start the season.

My fill water is pretty darn hard. It's Los Angeles city water but must contain a lot of calcium. A test strip shows my fill (tap) water with TA around 120 and pH around 7.6 or so.

The workup at the pool store was as follows:

FAC 5ppm
pH 7.2 - 7.4 (this is a little low because I've been trying to lower my TA)
TA 90 (they said this is perfect for gunite but my guess is that I want it lower)
calcium hardne

What I meant to say is - if you tell me the TH, Jock Hamilton's chart will tell you where your TA should be. So without knowing the TH, Jock can't help.

Using Bob Lowry's saturation index spreadsheet (which he posted here, and which I can e-mail you if you want), here's my suggestions:

Assuming TDS, including the salt = 4,100ppm
Calc. Hardness 380
Temp 77 degrees F,

If pH was 7.6 and TA was 120 - water would be balanced.

Hmm, well one of our assumptions must be wrong then... my TA is usually about 100 - 120 and if I get the pH down to about 7.4 it will creep up right past 7.6 and into the 8+ range in a matter of days.

In a plaster pool this is very common regardless of the TA.

That's why Jock Hamiltons chart is so good. get the Total Hardness reading and then we'll know exactly where you TA should be.

Examples:
TH 100 - TA 100
TH 250 - TA 85
TH 500 - TA 70
Jock recommends dumping water if TH is>500 and
>300 above fill water.

I stopped by Leslies yesterday but they had no idea what Total Hardness meant. They offered to measure my Calcium Hardness, which was measured last week at 380 ppm.

So how do I get a Total Hardness reading? If there's a kit I'm happy to do it myself.

Mike

I think I ordered my TH test kit from United Chemicals. Cost is minimal.

Okay, I noticed that Leslie's Pool online sells AquaCheck Orange 

strips that claim to test Total Hardness.  I took another look at my 

own AquaCheck strips and it labels the hardness pad as "Total 

Hardness (as CaCO3)" -- so is that total hardness or Calcium hardness?  

Either way, the pad reads about 400 which is pretty close to the 380 Ca 

hardness that Leslies measured last week.



Here's where I'm at so far; any advice on reducing my acid demand 

would be appreciated:



DATE        pH     TA   TH   TCl  FACl  Action

--------    ---    ---  ---  ---  ----  -------------------------

05/23/06    7.2    100        4         after adding 1/2 gal. Acid then 9oz Red Devil NaOH

05/25/06    7.5    120        4        

05/27/06    7.6    100  400   3    3    added 1 qt. Acid + 1 qt. scale prev.

From my experience, a calcium hardness of 380 would mean TH is 500(+). TA should therefore be 80 - but if you got it down to 90 you'd be close.

Assuming my fill water is pretty darn hard as well, would it be worthwhile to try to reduce the TH? What's the difference between a chelating agent and a sequestering agent?

Jock's recommendation is: If the pool water TH is 500ppm or greater, AND at least 300ppm above the TH of the fill water, then change the water. If the fill water TH is within 300ppm of the pool water, there is not much point changing the water. Just live with it and get the TA as close as you can to the recommended level (90, 80 or even 70 if you can).

Right now the TA is at 70 -- I'll see how the pH does with that. It was 6.8 yesterday, I added about 3" of fill water but otherwise left it alone to let the low pH work on my scale a bit, and today it measured 7.0. If it's 7.2 tomorrow, then I'm back to needing almost 2 gallons of acid per week, which seems pretty out of control to me.

Can I reduce the TH with a sequestering agent?