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Waterfall Underliner and Drain Details

 waterfall building waterfall drain

These illustrations show an installation technique for a waterfall. We use this liner profile when area substrate does not allow for a conventional waterfall pocket to be constructed: (see WF_Construction.html)

 Layers of building materials: 

     Compacted sand against compacted soil
   Layer of steel-reinforced concrete (2" - 2 1/2" thick)
   45 mil EPDM flexible liner
   Layer of steel-reinforced concrete (2" - 2 1/2" thick).

  A water retention pocket should be provided for the waterfall stonework to be built within. Without this step, leaks are probable. The retention pocket which is located under the waterfall acts as a "bib" and returns water to the pond. One of the least expensive and simplest methods for creating this retention pocket is with the use of 45 mil EPDM flexible liner material. The illustration at the top of this page depicts a liner under the waterfall stonework.

  As a general practice, on most waterfalls, we prefer to install 3" drains at the lowest pool on the waterfall prior to water returning to the pond. This provides the pond owner with the ability to open this drain and literally hose down the waterfall as you would your driveway. This feature dramatically reduces maintenance. This drain eliminates waste collected in the waterfall from entering the pond.

  Waterfall rock work is then mortared to the top layer of concrete. This method protects the liner from sharp heavy rocks during construction. Note the use of drains in each pocket of the waterfall. Over time, these waterfall pockets collect waste materials, which can be easily drained off. Simple ABS male threaded cleanout plugs serve as plugs for these drain lines. Bulkhead fittings make the transition from pipe to liner.


Elevation Illustration

This illustration shows the proper elevations of a non-pressurized
gravity return feed biological filter located behind a waterfall.

  Note the relative position of the ultravolet light filter in the return line. Positioning the entrance and exit ports of the ultraviolet filter in a downward fashion reduces the opportunity for bacterial mulm to collect in the ultraviolet unit.

  Positioning the filter slightly above and behind the waterfall is necessary. The further you move the filter from the waterfall, the higher it needs to be positioned: 1/4" higher for each 1 foot added distance.

UV InstallationUV Installation

See also: Waterfall Weir Chart and Calculations for Flow Rate

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