Hydraulics

Aquatic Technology Pool & Spa
Paolo Benedetti

Custom high-end luxury swimming pools and spas should have "engineered" plumbing systems (hydraulics). Not only infinity edge, vanishing edge, and perimeter overflow pools, but every singe vessel.

The hydraulic systems for the vessels need to be calculated, to stay below the MAXIMUM flowrates through the pipes. Flowrates (line velocities) are the most mis-understood component of swimming pools & spas.

It was estimated by the NSPI that over 95% of the swimming pools built do not comply with the industry standards for flowrates & line velocities.

This is why there have been evisceration cases, suction entrapment deaths, and hair entanglement drownings. This is not to say that these would not have occurred, but the severity of the injuries would have been significantly less, if there was merely less suction!

Now you're saying, but I need suction??!! You're correct, but a larger diameter pipe moving the same flowrate (gallons per minute) as a smaller diameter pipe, has a slower line velocity & therefore less suction.

We can still move the same amount of water (gallons per minute), but we can make the bather environment safer, ALL BY JUST USING A LARGER DIAMETER PIPE.

After the entire lengths of pipe, elbows, fittings, and equipment are calculated, the systems restriction to flow (friction) is determined. The maximum line velocities of specific pipe diameters are established by the standards & physics. However, a prudent mechanical engineer will strive for a lower line velocity than the standard. It is easier on the piping system, pumps don't have to work as hard, there is less noise, it provides a margin of safety if the system is modified, and smaller pumps can be used (ENERGY SAVINGS!).

A larger diameter pipe provides less restrictions than a smaller diameter pipe. Sized properly, the need for sweep elbows or specialty fittings to reduce restrictions are eliminated. The need for specialized anti-entrapment devices & plumbing methodology are eliminated.... merely by understanding physics.

So why don't pool builders use larger pipes??? Good question... lazy, added cost, ignorance, indifference, difficulty in plumbing - take your pick. I have had other pool builders attempt to build my designs, only to down size the pipes ("they are TOO big"), shorten beach entrances (there is a minimum design standard for a 7:1 slope), replace expensive stainless steel or galvanized rebar with regular rebar, or eliminate other details as "unnecessary" or "over-kill."

When I get a call that something wrong with my design, a gravity drain is not flowing properly (remember, it was downsized because it was "too big" ?), the beach is too steep (they shortened it & thereby increased the slope), or are experiencing rebar rusting through an element (because they deleted the corrosion resistant rebar), I point out how they chose to go with the low bidder. They were the low bidder for a reason...

The manufacturer of an anti-entrapment device (a vacuum release widgit) has been lobbying legislators in many states, trying to make it a law that their device (or ones like it) are installed on every pool. But if the legislators & building officials understood the physics & fluid dynamics of mechanical systems, these entrapment issues could be avoided with simple math.

The benefit of a properly designed system, is that the pumps are actually chosen LAST! After all of the systems' design parameters have been established, then a pump is chosen. The pump is selected to fit the need based upon the pumps' optimum efficiency range (pump curve).

An "engineered" or designed hydraulic system results in the use of smaller horsepower pumps, saves energy, moving more water, pumps make less noise, and resulting in a safer bather environment.

As you can see, a properly designed project will make the vessels operate correctly, without all of the faults that have inherently dogged the swimming pool industry.


Paolo Benedetti - Aquatic Artist
"Creating water as art."™
Aquatic Technology Pool & Spa
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