What Makes a Pool Fast?

There are seven basic factors specific to pool design and operation that maximize the performance of swimmers and make pools fast. While they don’t exist in any order of priority, some are more essential than others.

Indoor Air Quality

Most people are familiar with the “swimming pool smell” encountered when walking into some indoor pool environments. That strong smell can even be picked up at an entry lobby before even setting eyes on the pool. The smell is actually chloramines off-gassed from the swimming pool. They tend to reside close to the water surface, which is unfortunate for swimmers, as this coincides with the breathing zone. Highly-competitive aquatic athletes are familiar with pushing their bodies aerobically and anaerobically. In either state, heavy respiration of chloramine-laden air inhibits performance. The good news: there are several ways to dramatically improve overall indoor air quality, and in turn, maximize swimmers’ performances. One involves using proper air distribution over the surface of the water. Another option is to remove chloramines at their point of formation. Medium-pressure UV systems can be installed to help maintain chloramine levels to 0.2 parts per million or less. These systems destroy chloramines during the recirculation process. With improved overall indoor air quality, swimmers’ performances and health are improved as well.

Water Clarity

Pool water must be clear so swimmers are able to see underwater. Clearly, being able to see markings and wall targets allows for swimmers to time their strokes into their turns and finishes, as well as break out from their underwater kicks. Water clarity largely comes down to maintaining ideal water chemistry and water filtration. Newer regenerative media filters on the market in the last 10-12 years in the United States are gaining popularity for projects pursuing sustainability. These filters consume considerably less water than traditional high-rate sand filters. However, they also filter down to 1-5 microns, while sand filters often only capture particulate down to the 25-50 micron range. Ideally, the water must have a turbidity level that does not exceed 0.5, measured with a nephelometer.


It’s important for swimmers to be comfortable in the water, which means that water temperature should be approximately 78 degrees Fahrenheit. At this temperature, swimmers’ bodies will not overheat at maximum effort and stress. At temperatures much below this level, swimmers usually complain of stiffening muscles. Additionally, the body will be burning more calories to offset the colder skin temperature. At water temperatures much above 80 degrees, swimmers usually feel sluggish and experience an undesirable rise in body temperature during maximum effort. Something else for designers to consider are the hundreds, if not thousands, of spectators watching the competitive swimming event. These guests and their body height can cause slight differences in the rate of evaporation, and contribute to temperature conditions within the pool space.


Good underwater visibility is the product of exceptional water clarity and light level above the swimming pool. For the highest level competition pools, some regulatory bodies require 100-150 foot candles of lighting over the water surface so that visibility for swimmers, as well as for the remote viewing audience, is satisfactory. This often requires direct illumination from above utilizing fixtures located directly over the water surface. With the overhead light source directed perpendicular to the water surface, light will penetrate the water medium and reflect off the white pool interior. Underwater lights increase the light level under the water surface not only as a source, but also as an enhancer to the reflected light. In this manner, it creates an ideally-illuminated environment for competitions.

Subsurface Turbulence

Subsurface turbulence can inhibit the forward motion of swimmers. This turbulence can be caused by water currents from the pool’s recirculation system, but this varies upon the type and location of the inlets. Circulation flow currents can be a problem if they exist in the bounded water volume of the race course. Of greater concern is the presence of rebound turbulence created by swimmers. This is more prevalent during starts and turns while executing underwater dolphin kicks. The turbulence reaches the floor of the pool, rebounds and returns to the surface in such a way that it interferes with the forward progress of the swimmers.

Surface Turbulence

Swimmers have long been aware of the difficulty of swimming through rough water as compared to a smooth, flat surface. It’s this basic understanding that led to the development of floating lane line dividers, and subsequently to the wave-quelling designs used today. Floating lane lines absorb and contain wave energy created by swimmers within each lane. The primary benefit of contemporary lane lines is to isolate the turbulence in one lane, and impede it from crossing into adjacent lanes.

We also tend to see the dissipation of surface turbulence inside the lane where swimmers have created agitation. Essentially, when swimmers swim down the lane, they create surface turbulence that impacts their speed when returning through the original point of dissipation. As a result, the swimmer experiences greater impedance at the first third of each length, with the exception of the first length. Conversely, the least impedance occurs in the last third of each length when the surface has experienced the longest period of time from the last surface agitation.

Psychological Influence

Psychological impact is a subjective variable that positively or negatively influences all athletes at the start of a race. While the mental attitude of swimmers cannot be influenced directly, there are several things designers can do to heighten the excitement and adrenaline levels of the athletes.

Design architects should educate themselves about the procedural experience of competitors. There are identifiable psychological impact points from arrival at the facility, to locker room preparation, to warm-up routines. Energy builds up as more and more athletes arrive, and as the start time draws nearer, there are behavior patterns each competitor carries out. Typically, we see competitors isolate themselves, meditate and concentrate on the task ahead of them. Privacy may be an empty room, a corner under the stands or simply a towel over the head. For high-end competitions, a ready room is provided. The location, design and appearance of this room can be a huge motivating factor for swimmers.


If all of these environmental conditions come together just right, your facility will understandably be known as a “fast pool.” Swimmers will be capable of reaching their full potential, and you’ll see more personal best and record-breaking times at your facility.

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