On 31 Mar, 10:03, Rod wrote:
wrote:
Thanks guys....

The concrete was to be used to strength with the fibreglass over it.
However, with the second option, I could just put the fibreglass. Not
sure about the weight though.. I suspect I might still need something
under it for strength.

As for the waterfall absorbing the water, I have been thinking about
this. Another issue is, ultimately, I want a little stream to a second
pond (where the pump will actually be). This will obviously mean a lot
more water is needed before it starts recycling. Waterfall needs
filling, the stream needs filling etc. The bottom pond will be deep
(for volume) but have shallow / rocky sides so you won't see the water
level drop drastically.

To aggravate the situation, I don't intend running the pump all the
time. This means I cannot "get it started and top it up".

Maybe I am being to ambitious

Have a third "pond" - actually a covered tank of some sort. A small weir
from the second pond to the third.

So you pump from the third pond to the top. When that water gets to the
second pond any excess over what fills that pond goes over the weir into
the third pond. By being covered you don't notice the level of the third
pond at all and that of the second remains static.

You will also need to have a means by which the third pond can lose
excess water when there is heavy rain.

(I used to have a house which had a single visible pond and a waterfall
down a cliff-like face. This had a hidden second pond. The arrangement
didn't work properly as the concrete was porous and had cracked, but the
idea was fine. The hidden pond was very popular with frogs...)
--
Rod

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This waterproofing this is a big issue. We had a nice waterfall
feature ruined by a tear in the liner somewhere underneath the rocks !
Simon.