Why Is Correct Ph Necessary?

[steve haigh]

hi all

i know the holy grail of pool chemistry is ph needs to be 7.0-7.6 but why? is there any problem with it been as lower?

i ask because i can't raise my pool ph. i don't know why. i've added about 20kg of soda ash and it will not change ph. it just clouds up white like the soda ash will not desolve. i'm thinking of giving up and leaving it at 6.8 or below.

any thoughts?

thanks, steve

[steve haigh]

i think i just answered my own question on this site

http://www.havuz.org/pool_pool/pool_mainte..._testing/ph.htm

What happens when the pool is too acidic?

(pH is low)

If your swimming pool is Marbelite or plaster, the pool water will begin to dissolve the surface, creating a roughness which is ideal for pool algae growth. A similar result occurs in the grouting of tiled swimming pools.

Metals corrode - and this includes swimming pool equipment, pipe fittings, pump connections, etc.

As the swimming pool walls and metal parts corrode, sulphates are formed. These sulphates are released from the water onto the walls and floor of the swimming pool causing ugly brown and black stains.

Chlorine, which is used as a disinfectant in the swimming pool water, is activated and lost to the atmosphere very quickly. The water is not being sanitised, and we are throwing away our money by adding chlorine when the pH is too low.

When we swim, our eyes and nose burn. Our swimwear fades and perishes. Our skin gets dry and itchy.

*******

so i'm not sure what to do short of emptying the pool and refilling, but my city water is so acid, i think i'll be back at square one of i do that.

[Strannik]

It's possible that you have something that buffers pH in your water.

Did you only test for pH or other parameters as well (like TA, CH etc)?

If so, can you please post all the numbers?

[steve haigh]

It's possible that you have something that buffers pH in your water.

Did you only test for pH or other parameters as well (like TA, CH etc)?

If so, can you please post all the numbers?

i only have the basic heyward kit that test chlorine and ph. i'm trying to find a test kit that includes TA and CH.

however, i read this: http://www.havuz.org/pool_pool/pool_mainte..._alkalinity.htm

Total Alkalinity

The total alkalinity (TA) is a measure of how much of the alkaline substances there are in the water. In the swimming pool water, we are concerned with bicarbonate alkalinity, which should be between 80 ppm and 120 ppm.

When the total alkalinity (TA) is within this range, it prevents rapid pH changes and "stabilises" the pH level.

If the TA is too low, Marbelite and plaster walls will become etched, metals corrode, the pool's walls and floor can stain, the water can turn green, eyes burn and we can have pH bounce (pH rapidly going up and down, seemingly at random).

If the TA is too high, the pH is difficult to adjust, the water becomes cloudy, the pool constantly needs acid (according to your test kit) and the chlorine loses its efficiency as a disinfectant.

$$$$$$$$

are you suggesting my TA may be too high and that's why i can't adjust the ph? is it possible to have TA too high but ph too low? the info above implies its more likely that if TA is high, ph is too high and hard to bring down.

thx steve

[chem geek]

It is possible for TA to be high and pH low, but it's unusual because if the water is exposed to air and especially if there is aeration, the pH of the water will tend to rise. If the Cyanuric Acid (CYA) is very high, then it can also be a strong pH buffer where aeration won't help. Perhaps you are using Trichlor pucks/tabs in high quantity and these are very acidic which is the source of your low pH and would also contribute to CYA. Nevertheless, you should be able to add sufficient pH Up to get the pH to rise or you could add 20 Mule Team Borax if you wanted to raise the pH with less of a change in TA or you could try aerating the pool and stop using the Trichlor (use chlorinating liquid or unscented bleach instead) as your source of chlorine.

To really know what's going on, get a good test kit -- the Taylor K-2006 you can get at a good online price here or the TF100 from tftestkits.com here with the latter kit having 36% more volume of reagents so is comparably priced.

Richard