Wierd PH readings...

[poolmom06]

I tested it again and it said 6.8 so I added 2 pounds of Borax to pull it up... how long until I can test it again? I was gonna turn the pump off tonight to let the dead algae settle for vaccuming but I may wait till later...

[Watermom]

I usually wait 3 or 4 hours after adding Borax before retesting.

[bradjo]

Chlorine over 10ppm converts phenol red to chlorphenol red (dichlorophenolsulfonephthalein), Chlorphenol red measures pH from about 5.2 to 6.6 if memory serves turning a dk purple at 6.6 unlike phenol red which is dk purple in the 8's. So you can make a serious error here.

Thiosulfate is base and can give a false high pH reading here's where a 44 ml sample for pH is a good thing.
hth,
Jo