Mikepier wrote:

-snip-
They stress it is important to install on a level surface. I wanted to
install it on a concrete area in my backyard ( on thick padding ) but
the concrete is pitched slightly away from my house.

One other thing to consider before you install it. Remember that it
holds about 1000 gallons of water. Where will that water go if
there is a sudden release of all of it? [all it takes is a drunk
sitting on the edge-- or trying to jump over it and failing]

If there is a cellar window right there do you have anything that
can't take good rinsing down there?

Jim