> Thanks, the plan is to put a patio slab under the drain and then cement > the > drain on top of it. The skimmer will attach with a bulkhead opposite the > waterfall. > > How much below the pond bottom should the drain opening sit? 3/4"? > The bottom of the pond should be graded to be smooth with the top of the bottom drain with the clamping ring on. It does not need to go any deeper. If it is set too low, there won't be room between the cover and liner for water and debris. It is always good to bowl the bottom to make it easier for the debris at the wall to find its way to the bottom drain easier, but if it is bowled much, it makes it difficult to walk to the edge to get out if you get in for any maintenance. -- RichToyBox http://www.geocities.com/richtoybox/pondintro.html Zone 7A/B Virginia