Water Feature Pool Design and Detail
The design of the water feature catch pool is very important and can affect the expected outcome of the feature. First of all, the size of the catch pool must be considered. To determine the size of the catch pool, the type of nozzle and spray requirement, wind, evaporation and draw down must be considered.
Each type of feature has a required space needed for the catching of water and spray. Winds usually up to 10 mph before an automatic cutoff takes place will displace water that needs to be caught so that passing people are not getting wet and during the winter months an icy film does not develop. Also, there may be a turbulence caused if the pool’s surface area is too small. This is common with the vertical nozzle in a round or equal spaced pool and waves bouncing back toward the feature. Turbulence can disrupt the feature’s performance, so calculation of surface area is important as well as placement of nozzle. Evaporation and draw down must be considered in surface area and depth of a catch pool so that enough water can be supplied so hydraulics is not compromised. The water depth in a water feature pool should not exceed 18”, as it would then need to have a compliant barrier.
The pool design must include water stops on all through-wall fittings of a non-corrosive material. Brass or copper bond well with concrete and are recommended. A drain/overflow fitting must be installed and sized to be able to drain excess water and then the standpipe removed when complete draining is needed. A complete drain also needs a positive slope of 1% of the pool floor to gravity feed the drain. The size of the drainpipe should be sufficient to drain the pool in a reasonable time, depending on the overall gallons of the pool. A minimum of 2” drainpipe should be used so that it does not easily clog with debris.
If there are multiple pools or holding areas, equalization lines are used to connect them with gravity used to fill. Where suction lines are used, it is important to use a cover that prevents a vortex or whirlpool from forming, which can causes cavitation, which is damaging air in the pump. The cover has to be able to accept the gallons per minute the pump has at maximum use as well.
The color of a pool is preferred to be dark so that dirt does not show easily. Also, reflection-type pools should be very dark or black to increase the reflective effect. Coping on the edges should be smooth.
If any of the design requirements are not followed, the entire water feature can fail.