Confused about ideal pH

[tfoggo]

I notice that the Pool School's recommended pH level is 7.5-7.8.

Everything else I've ever seen (pool chemical labels, pool equipment manuals, web articles etc.) suggests it should be 7.2-7.6 with 7.4 being optimum, and have consequently spent a lot of time and money trying to keep my pH inside those parameters (it tends to drift towards the high 7s)!

Is this a climate/temperature thing (I'm in the UK) or have I just been suckered into buying more 'pH Minus' than I really need?!

 

[borjis]

7.2 - 7.8 should be safe to swim in and for most equipment, but I aim for 7.5 because that's roughly the ph of the human eye/tears is.

my 002 cents.

 

[duraleigh]

Actually, 7.2 - 7.8 is just fine. There is more latitude in pH than folks think.

BTW, you can substitute muriatic acid for pH minus....not sure if it saves you money in UK.....it does in US

 

[tfoggo]

Thanks both. Very helpful!

All the best.

 

[JoyfulNoise]

The 7.4 optimal numbers comes from the mistaken idea that your pool water needs to be at a pH close to human tears. It's basically pseudoscientific poppycock. Your tears are perfectly capable of buffering pool water anywhere in the 7 range. Irritated eyes comes from combined chlorine being too high and rubbing ones eyes after emerging from under water.

So the optimal pool pH is anywhere in the 7 range where your pool water naturally wants to settle at. For many pools, you need to lower TA to keep pH rise under control. My TA is 50ppm and I have 50ppm borates in my pool water. I never lower my pH below 7.6 (unless I'm trying to actively lower TA) and I don't add acid until my pH rises above 7.8. My pH will hang at 7.7 for well over 10-12 days and I typically add acid about once every 14 days or so.

pH Down is sodium bisulfate. It's not generally recommended to use here because you can build up sulfates in your pool water which are detrimental to plaster and SWG cells. Muriatic acid may not be generally available in the UK, but if it is, it's a better choice.

 

[tfoggo]

Brilliant. Thank you.