Cement in concrete hydrates producing the hardened paste, heat, and calcium
hydroxide. The calcium hydroxide has a pH of around 13. The calcium
hydroxide will continue to leach into the water over a long period of time.
You can significantly reduce the rate of flow by allowing the concrete to
completely dry for a few weeks. The carbon dioxide in the atmosphere reacts
with the calcium hydroxide to make calcium carbonate at the surface of the
concrete. This carbonation layer is very dense, blocking the pores so that
the calcium hydroxide has a much harder time migrating to the surface.

Calcium hydroxide is probably the cause of your high pH and it will not show
on a KH test kit that measures carbonates. You have in essence an
unbuffered high pH. Do not use vinegar. If you are going to do an acid
wash, use muratic acid, masons use it to clean brick, and use it before the
drying process. I don't think that you will need to use the acid, just let
Mother Nature fix it.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"Rand Simberg" wrote in message
...
On Mon, 30 Jun 2003 05:53:05 -0700, in a place far, far away, JSin
made the phosphor on my monitor glow in
such a way as to indicate that:

Look to the lime in your mortor if you are running at 8.o and rebounding
that hard it is being buffered by the the mortar. What is your Tap water
pH???

It's the same, as best as I can tell from a color test (don't have a
meter--a tad over 8, maybe as high as 8.2.

I would bet it is 1 or 2 points lower and I will guarentee your
supplier is running a lot lower especially in thier feeder tanks where
you have a huge bioload and a lot of organic material.

Well, the new pond and the tap are the same, as far as I can tell. My
healthy patio pond (that is replenished regularly from the tap) is
7.6.

But as you say, the fact that it rebounds so quickly from the acid
does indicate a lot of continuing buffering. I'll have to go out and
get a KH test kit, I guess, to really know what's going on.

I've never tried running vinegar over the mortar. Would that help?

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

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