Re: PH crashing up?

[Chuck H <grendel at usit_net>]

C. Alan wrote:

> The water I am using is a mixture of RO water, and tap water.  I add a 
> little baking soda, Kent's RO right, and some Kent's PH control 
> Minus.  After mixing for about 24 hours, my change out water has a Ph of 
> around 6.5, A GH of 2, and KH of 2.
>
> What is happening is this:  I add my mixed water, and the PH drops down to 
> around 7.  Within 24 hours it will rise up to around 8.4!  I tested the 
> KH, and it is still at 2 or less in some cases.  So what is driving the PH up?

What you're seeing is called "pH rebound" or something close.  Basically, 
the buffer in your tap/tank water is strong enough to throw off the effects 
of the softer water.  I have a nice explanation of what is happening 
chemically stowed away somewhere.  I'll try to find it and send it to you 
if one of our more chemically enlightened list members doesn't feel called 
to elaborate.

Are you cutting your tap water with RO water to drive hardness and 
alkalinity down?  If that's the case, I don't see why you would add bicarb 
and the Kent stuff to the change water.  Just add enough straight RO water 
to your tap water to get the hardness and alkalinity down to where you want 
it.  For the water already in the tanks, do a few changes with straight RO 
to gradually get parameters down.  There's no need to mess with all those 
chems.
--
Chuck Huffine
Knoxville, Tennessee