Alway adding acid - all numbers are great otherwise - ideas?

[alphadog]

So, I drained and acid washed this year to remove scale, so I paid extra attention this year. Aerated for about a week, to get the TA down, then added a little bit of Bicarb to raise it.

Currently TA is about 90-100, but PH rises every 2 days - I am guessing it is from my SWG. CA, CH, everything else great - but if I don't add acid every day or other day, I am at 8.0Ph or higher.

Is there anything else i can do? If this is normal, what do people do when they go out of town for more then 2 days?

The pool is crystal clear, and everything else is great. The SWG is dialed in to provide just what i need and not to much, so I don't think i can cut that back any (about 3ppm is what i am trying to maintain).

Thanks for any other suggestions.

22K gallon Gunite/plaster.

 

[JoyfulNoise]

If you acid washed, then you likely exposed some underlying plaster that can raise pH until a layer of calcium carbonate can form.

As for pH rise, just drop your TA until you find a value that lets you go longer between additions. There's nothing magical about the TA values in the Recommended Ranges. If you go as low as 50ppm or 60ppm and you're still having serious acid demand, then you can consider borates. But try dropping the TA first.

As a personal example, my pH is very happy when my TA is 60ppm.


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[alphadog]

Thanks, I had my TA at 60 PPM and it seemed to demand acid still - so i thought maybe it was too low. From the Taylor kit, i thought that to low or to high would cause bounce, so I raised it from 60 to about 90 - still the same bounce.

Sounds like i need to read up on borates.

My pool is about 5 years old, and I have always had an acid demand problem, but in the past my TA was way too high.

 

[JoyfulNoise]

Aside from the SWG, do you have any other sources of aeration - waterfalls, bubblers, deck jets, spillways, etc. ?

What is the TA of your fill water?

What pH are you trying to target?


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[alphadog]

I would have to check fill water, but have not had to add any with rain this year. No water features - I do have in floor cleaning system, but it doesn't aerate. I would like to see my pool stay at 7.4 to 7.6 for some period of time.

it seems like it was more stable after the aeration for quite a few days at the start of the summer but then it went back to being a demand hog.

if my easy recourse is to add a cup or two of acid every two days, are there any suggestions for when I travel and there is no one to do this?

 

[JoyfulNoise]

A pH of 7.4 may be unrealistic. In your case I would advise dropping your TA to 50ppm (if possible, depends on fill water) and targeting a pH no lower than 7.6. Your range should be 7.6-7.8. The reason for this is that the lower TA and slightly higher pH will keep your CSI negative BUT carbon dioxide out gassing is slower at higher pH. Your pH rise is dominated by how quickly CO2 out gasses from the water and the concentration of CO2 is higher as you lower the pH.

As for pH maintenance during vacation/business trips, you could try to use trichlor picks in a floater if you have the CYA budget for it. Trichlor is acidic and will lower pH and TA. If you don't have the CYA budget, then you just might have to let it ride. Brief exposures to positive CSI is not necessarily going to scale. Pools can go as high as +0.7 for short periods of time and not experience any scaling. Remember, CSI just indicates if scaling is possible, it says nothing about the rate of scaling or if it will initiate.


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[duraleigh]

Drop your TA down to 50 or so as suggested above. The time between acid additions should lengthen.

Borates is another buffering source but I would retry TA down at 50 ppm before I went to the expense of borates.

 

[alphadog]

Thanks everyone... will do some aeration to get back down to around 50 TA and see how it goes.