Forgot to also ask -

I have a DE Perflex system so I can't set to bypass. So, if I do open today here's a pH quandary I have:

I will test then add my box or two of Borax to get pH right before I start to shock - but I must add the DE powder to the system immediately so as not to damage the fingers of the filter. How long do you all think it would take for the pH to come up high enough before I can start bleaching the bejeesus out of it?