PH question

I went to the pool store today for some Boxer adhesive and while I was there I decided to get a free water check and here is what I found out:
CYA 60
Total Chlorine 3.7
Free Chlorine 3.6
pH 7.2
Total Alk 67
Adj. total alk 49 (don't know what that means other than adjusted)
Total hardness 68
My pool is a 24 x 52 above ground vinyl liner with 13,500 gallons. She said that my ph and alkalinity need adjusting (as well as calcium but I've been a member of this forum long enough to know that adjusting calcium is bull for a vinyl lined pool). I read in another post that a pH of 7.3 was okay so I am wondering about my 7.2. Also, when I do the alkalinity test at home my reading is 120. I use bleach to shock. I have a feeder so I am guilty of using Trichlor (I'm not home all day due to work and have had mustard algea problems the last four seasons so I don't want to chance not having a full feeder of chlorine). How much Borax should I put in for the pH or should I just do nothing? The water is clear. This really cracked me up, there was a lady in the pool store ahead of me getting her water tested and the girl told her that she needs 20 bags of shock and a whole list of other products. I just about dropped my teeth. They are selling shock for $3.99 a bag. I did hear that her pool was the same size as mine. I only go in for something that I have to have and always tell them that I have all the chemicals I need at home. Well, sorry for the long post. I'll be waiting for a response. Penny

I wouldn't lose any sleep over a pH of 7.2 but keep an eye on it and if it drops any more (it will if you are using trichlor) then add borax to raise it. A good rule of thumb is that you are going to need twice as much borax as you would soda ash (pH increaser). With your CYA at 60 ppm I would raise the FC to about 6-8 ppm and when you need to shock shock to 15 ppm. I would not put much faith in the pool store testing. I can tell they are using test strips and a strip reader because they tested total hardness and not calcium hardness! Actually, I would be suspect of all the readings they gave you for this reason!

The adjusted total alkalinity is your true carbonate alkalinity after subtracting the alkalinity from the cyanurates in the water. Some people feel this is important since cyanurate do not contribute to pH stability, only the carbonates. Personally, I feel that adjusted alkalinity is only important when using stabilized chlorine like trichlor. A quick and fairly accurate way to get an adusted alkalinity reading is to subract 1/3 of your CYA reading from your TA if you pH is between 7.4 and 8.0 and to subtract 1/4 of your CYA reading from your TA if you pH is 7.0-7.2.

Edit: If your CYA is truly 60 ppm and your TA is 120 ppm then you would have an adjusted TA of 105 ppm with your ph of 7.2. Not exact but close enough for government work!;)

You were right about the strips. I have a pretty good drop test kit that I use at home. When I tested my chlorine when I got home it was reading about 5. Do you think there test was also off because the water had been sitting in my car all day in 95 degree heat? I just mainly wanted to get the CYA reading but now I wonder how accurate it even is. Also, do you think I should go back to just using bleach for chlorine and only use the feeder when I am going to be out of town? I had been turning my pump off about 12 hours a day but it seems that when I do that I either get cloudy water or a small algae bloom. I have no idea what my electric bill will be running the pump 24/7 but I'd rather have that than a pool full of algae that won't go away. I am looking into a newer pump that uses less amps (mine uses 13.8 and is very old). I would like to get a 2-speed but that's a whole other thread. Thanks again, Penny

Penny, nice to meet you!:)

With the exception of the CC being ~ 1ppm and the alk being slightly low - the numbers look good. The 'adjusted alk' takes into account that the cya registers as part of the total alkalinity, so is adjusted for it. 4 lbs of baking soda should get you to 80 on the 'adjusted' reading, which is fine (usually).
The ~1ppm combined chlorine is more important (IMO). FC + CC = TC, so you've got something in the pool that the chlorine is attacking, you need to raise the FC enough to kill whatever's in the water and keep it raised until the CC = ~0.
I think that you've got more than enough cya in the water and should stop using the tri-chlor tabs, use bleach at night to sanitise your pool, the tabs just increase the amount of chlorine you need to keep in the pool, and drop the pH.
7.2 for pH is fine, but you don't want to go any lower.

Please realise that I'm not a chemist but the advice I've given comes from years of experience and years of reading this forum:)

edit: I will always differ to Evan on questions like this - I'm just such a slow typist that his response - and yours (!) beat me into the forum - edit

LIke I said they are using strips and I would find all of their readings suspect. Get yourself a good kit such as the Taylor K-2006. It will test all the water parameters you need!

Hi Penny
We got our 1 1/2 H.P 2 speed for $229.00 here :
http://www.poolsupplies.com/parts/waterway-hiflo.asp
So far we really like it. It is very quiet.

~Hoffmans

Next time you look at your pump can you tell me how many amps it uses on low and high? I;d appreciate it.

Penny,
Here's a picture:
I guess it is 8.8 on high and 2.6 on low.

http://i73.photobucket.com/albums/i2...torbiglast.jpg

http://i73.photobucket.com/albums/i2...pmotorbig3.jpg

http://i73.photobucket.com/albums/i2...pmotorbig2.jpg

http://i73.photobucket.com/albums/i2...mpmotorbig.jpg



I hope this helps.
~Hoffmans

Thanks Hoffmans, that is exactly what I need to upgrade to. I appreciate the pictures too.

Is there a formula for how much acid to add to lower PH a certain level? For example, on a 22k gallon pool with a PH of 7.6 how much acid should I add to get it down around 7.0-7.2?