EDGEucation
by Benjamin Lasetter
We are in the midst of a renaissance for the pool industry. The residential pool has evolved from the old “kidney” pool with a baby blue 6” waterline tile and a 8’ diving board to a complex mechanical and structural system balanced to perform as a work of art. Details that used to be reserved for the pools of the rich and famous are now being executed with precision on much tighter budgets due to groups like Tributary Revelation sharing ideas, techniques and mistakes. One such detail we have a lot of experience with is the perimeter overflow, which can be broken down in to three major categories: Submerged Coping, Raised Beam, and Knife (Lautner) Edge. In the following chapters I will discuss some of the technical aspects of each.
The first detail I want to discuss is the Submerged Coping overflow. With this style bond beam, you essentially have two pieces of coping with a slot between them that opens to a concealed gutter. The gutter then carries the water to a reservoir to be recirculated. Benefits of this detail are its simplicity in construction and it allows you to bring your water level up to the deck level to create a clean modern look. I believe this is the most simple overflow detail because for most installers, they are already using these same installation techniques when they install regular coping, they just have to construct a gutter and get their hydraulics right (that’s a whole different story). Where do people mess up with this detail? Many people don’t consider the texture and surface area of the submerged coping. A rough stone with a lot of surface area will add resistance to water in transit over the edge, so you may have to beef up you overflow pump and plumbing for this overflow.
The Raised Beam is a detail that almost every pool builder should have experience with since it is essentially the same detail as a vanishing edge. With the raised beam, you can slope the top of the beam as you please, I usually prefer to slope mine down from the waterline on the outside edge to the bottom of the tile line on the inside edge. Having this edge line up really finishes nice and clean! As the water overflows the edge or weir, it dumps into a basin, trough, gutter, etc. When you have a basin, you have the ability design a wide body of water to catch any water that project over the edge, but when a trough or gutter is on the other side you have to be cautious because bather surge, wind or normal water projection from the weir may dump water beyond the structure designed to contain it!
And finally, they most complicated to execute is the Knife Edge, commonly known as the Lautner Knife Edge. The Lautner Knife edge was conceived by the famous architect John Lautner and first executed by John Lautner and David Tisherman on the Sheats-Goldstein Residence in Beverly Hills in the early 1990’s. The idea was to have a perimeter overflow gutter pool (similar to a competition pool), but to bring the water level up to the deck level. The detail most commonly used today is an improved version of what Lautner and Tisherman conceived almost 30 years ago. We currently have 2 Knife Edge pools under construction and I have built 7 in my career (Proudly, one of our pools is the top image in a Google search of “Lautner Edge Pool” Thank you Tributary Revelation and Pinterest!). Each time we have built one, we have made a few minor changes in construction methods and techniques as well as plumbing, but we still use the basic shape and geometry that the Genesis guys came up when I was still in high school. Why is it so difficult? It involves cantilevering stone over a trough, leaving a ½” gap between the weir and the stone and having the confidence to set that stone knowing you will never pull it up to access the concealed gutter and plumbing all while dialing your weir edge tolerance to < 1/16”.
Remember, all of these details need to have their plumbing and pumps properly sized for the chosen overflow effect because the chosen materials and desired effects will have a dramatic effect on the finished product. Additionally, I have to stress the importance of multiple layers of waterproof protection of your concrete shell when building any overflow detail. Improper waterproofing will undoubtedly lead to increased maintenance and cleaning as well as premature failure due to water migrating through the shell.
