It’s not as glamorous or exotic as imported Turkish marble or as soul-stirring as a winding, intricately landscaped stream put together one boulder at a time. It is plumbing with some machinery attached.
But a waterscape’s hydraulic system requires at least as much care and attention as the finest materials or most high-tech of gadgets. To make your concept work, you need to control how and when the water jumps, falls, sings, and stays quiet. Plus you must ensure that it lasts. For this to happen, the pool builder must adhere to basic hydraulic principles. These principles should be respected not only by pool contractors, but also by the designers and builders who collaborate with them.
Here are five hydraulics mistakes that every contractor/designer team should avoid:
Mistake 1: Big pumps, small plumbing To an uneducated consumer, a 2-hp pump sounds like a better buy than a ½-hp one. Builders hear it all the time: Potential clients turn to them and accusingly say, “Another builder would include a 2-hp pump, and his bid is less than yours.” That builder may be using smaller plumbing to cut costs.
Larger pumps—3 hp and up—have their place, generally on systems with large, gushing waterfalls or voluminously spilling vanishing edges. But bigger isn’t always better here. Conversely, plumbing is not the place to scrimp.
When sizing the pump and plumbing, the contractor must find an equilibrium, producing the needed volume while controlling system pressure. One guiding beacon is the water’s velocity. As you would guess, a larger pump will push more volume. That sounds good, but when pushed through plumbing that’s too small, it will speed up. Fast-moving water can wreak all kinds of havoc, including unwanted pump noise and premature wearing of the pump. After a certain point, extra speed introduces more pressure and turbulence into the system. And, in the absolute worst cases, it can cause suction entrapment, an increasingly publicized tragedy in which somebody becomes stuck on a drain and can’t pry themselves away.
Larger plumbing allows water to move more freely, thus slowing it down. It also reduces overall system pressure, since you don’t have so much water rushing to get through a smaller opening.
To hit the right combination, you want the pump just large enough, with plumbing that allows water to move at the right velocity—6 to 7 feet per second throughout the system and 1½ feet per second at drains.
Small plumbing of 1 to 1½ inches has its use, too, but only sparingly. It often feeds spa jets or pool inlets to help speed up the water as it enters the vessel. These days, most plumbing should be 2 inches or larger.
Mistake 2: Too many plumbing bends Plumbing elbows also add pressure and turbulence to a system. Water wants to move in a straight line. When it confronts an elbow, it bounces off the sides, causing turbulence as it works its way around the bend. The tighter the bend, the worse it is.
Builders want to avoid these bends as much as possible. That means they’ll need sufficient room around the pool and in the equipment area, so they don’t have to create a virtual spiral of elbows to fit a tight space. When the plumbing must bend, builders are better off using more sweeping elbows. A straight 90-degree corner causes a lot of turbulence. When possible, plumbers should use two 45s or a “sweep 90”—an elbow that gently curves until it completes its turn.
In addition, these elbows must keep a safe distance from certain pieces of equipment, such as pumps and filters. After exiting an elbow, the water needs time to smooth out before entering these key components.
