Skimmer

While the regeneration zone will filter small particulate matter, it isn't very good at removing things like leaves and grass clippings that float on the surface of the water which will eventually sink and litter the bottom of the pond, decompose and provide nutrients for algae to grow on.  That's were the skimmer should help.

Based upon a SWAG, I purchased an Atlantic "Big Bahama" PS7000 pond skimmer.  It is rated for ponds of 900 square feet of surface area and flows of 4000-7000 gallons per hour.  During the warmer months of the year our prevailing wind is from the south-west, so I decided to position the skimmer on north-east corner of the pond in hopes that surface debris would be propelled in the direction of the skimmer.  We pulled the liner away from that corner of the pond and Brian excavated a hole for the skimmer.  He used a laser transit to set the depth so that final water level (which is indicated by a raised line on the face of the skimmer) will be a few inches below the crest of the pond liner, which is about 18" above the top of the deep zone walls.  

Before placing the skimmer, I drilled holes on the skimmer walls for the 2" suction pipe, a 2" overflow pipe and an Atlantic Auto-fill valve.  The drill points had already been marked by the manufacturer so no measuring was necessary.  The auto-fill valve is similar to a toilet fill valve -- basically a float that allows water to pumped in to the skimmer when the water level drops, and shuts off water when the proper level is reached.  We ran some 3/4" water line in a trench from a nearby spigot on the house to the area of the skimmer, and used garden hose on each end to make the connections to the spigot and the skimmer.  

The overflow pipe on the other hand, which is about 2" above final water level, will allow excess water to gravity drain out of and away from the pond during the spring thaw or after a long period of rain.  It consists of just a length of 2" flexible PVC which we terminated with some rigid 4" pipe, which you can see here where it daylights outside of the pond.

The suction pipe is connected to flexible PVC and runs under the regeneration zone to the pump.  More on that when we get to plumbing the pond pump.

After this prep-work, the skimmer could be placed in its hole and the liner draped back over it.  A hole was cut in the liner for the skimmer opening and then the liner was attached to the face of the skimmer with a face plate, screws and silicone which were supplied with the skimmer.  We then backfilled the hole with soil and gravel.  This photo show the guts of the skimmer -- the suction pipe (which extends towards the bottom of the skimmer), clockwise from that is the bulkhead fitting for the overflow, then the autofill.  You can also see the skimmer's net just inside the door and its five brushes, which filter large debris from the water before it passes into the suction pipe.