Concrete for a pond is a job for a professional. Whether it is gunnite,
which is a very dry spray on concrete, or whether it is ready-mix that must
be placed in formwork, neither is a job for the untrained. The EPDM or
similar liners are much more forgiving.

If you use concrete, as soon as the concrete has been placed and finished,
and the workers are out of the pond, cover the surface with polyethylene
sheeting to keep the moisture in for the first week. Add water and leave
the water for a month. At the end of the month of curing, the concrete will
have most of its strength and watertightness. Because the hydration of
cement yields a lot of calcium hydroxide, it will cause the water to have a
very high pH( potentially 13). Drain the water and allow to air dry for a
couple of weeks to allow carbon dioxide in the atmosphere to react with the
calcium hydroxide to form a calcium carbonate (limestone) surface hardening.
This will make the concrete more watertight and reduce the ability of the
calcium hydroxide to migrate to the pond water. Also drying allows the
pores to dry of liquids filling with air which acts as a dam to water flow.
Fill with water and monitor pH. If it is climbing, above about 9, remove
the water allow to air dry for another two weeks and try again. If it has
not stabilized, then you should coat the surface with a surface coating like
Thoroseal, or pool paint.

Some of the skimmers on the market have concrete collars that can be bought
to fit them, and some of the bottom drains have a concrete extension for
going through the concrete, rather than the bulkhead fitting for rubber
liner.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"matt clark" wrote in message
om...
I am putting a new pond in my back yard. It is my first time doing a
project like this. I have pretty much got the hole dug at about 3'5"
and i have already purchased the rebar. My problem is that i cant seem
to figure out the best type of concrete to create a liner. I was told
gunite and portland. but im not sure. Also will I have to seal it
regardless of what type of cement i use? Soo many questions. Also if
anyone has any tips i would appreciate any help on sealing the drain
or plumbing tips.

Thanks in advance.