|Many non-swimmers wonder how one pool can be faster than another. After all, isn't water the same wherever you go? Any swimmer worth their salt knows that there is a huge difference in pool speeds. Below we go into some of the factors that make up a pool's speed or lack thereof (without getting too technical).|
Depth. As a simple rule of thumb, deeper equals faster. The primary reason for this is that shallower pools tend to reflect the turbulence that makes its way to the bottom back up to the surface. And, since water turbulence is a deterrent to speed, a shallow pool is bad. Some people, however, disagree with just how deep a pool should be. Many people believe that extremely deep pools are worse for the swimmer, although it is difficult to justify this through physics or hydrodynamics. The thought on very deep pools is that it hurts a swimmer's perspective. It makes it hard for the swimmer to judge where he or she is or judge the pace he or she is going. Swimmers often times complain of feeling dizzy or disoriented, or even experience slight vertigo (fear of heights) when swimming in extremely deep pools.
The minimum depth you should want for a fast pool is 7 feet. This gives the turbulence created at the surface enough space to dissipate by the time it reflects back towards the surface. Pools that get below 4 feet should not even be considered competitive pools. They may be OK to train in, but should not be used for racing. Pools greater than 15 feet in depth risk causing perception problems in some swimmers.
Another point of contention is whether the pool should be a consistent depth. We believe a consistent depth is better than a gradient for many of the reasons stated above regarding perception and perspective. A changing depth can sometimes play tricks on the mind. Temperature currents can also occur on a very slight level as warm water rises and cold water slides down to the deep end. We do, however, think pools with depth changes can be fast, provided they don't go below the threshold depth discussed above.
Water Temperature. This characteristic has as much to do with personal preference, and event(s) being swum as with actual science. Extremely warm or cold temps are bad for obvious reasons. Some swimmers like the jolt colder water gives while others feel like it tightens their muscles. Some swimmers like the warm water because there is no jolt and their muscled stay loose. Others overheat. As a result, your preference and experience coupled with the kind of event you are swimming will have a large impact.
Generally, upper 70's (Fahrenheit) is considered a good temperature, but this is highly debatable. There is little debate over the theory that temperature plays a part in a pool's speed. There is, however, a lot of debate over what is the ideal temperature. We believe, no one right answer will ever surface, but a range of temps for particular body weights and fat percentages and events may eventually surface. For now, just use your experiences as a guide.
Air Quality. This characteristic plays a large role in how the swimmers perform. Low humidity, relatively cool temperatures, low elevation, and clean air make for ideal swimming. Since the air a swimmer breathes provides the body's muscles with the oxygen to help it to perform, it only makes sense that better air equates to better swims. As most parents of swimmers know, good air quality is rare in most pools. But as anyone who has ever swam at some of the best pools in the world will tell you, most of the fastest pools have excellent climate and air quality.
As with water temperature, most people agree air quality makes a large difference, but exact ideal settings for all swimmers are unknown.
Chemical Treatments. Just like putting salt in water can increase the buoyancy of an object in the water, the chemical treatments a pool uses can help or hamper swimmers' performances. The pool treatments used can affect the water qualities and the air qualities in a particular pool. We won't go into any detail here, but just know that it makes a difference.
Gutters. Swimmers at the IUPUI in Indianapolis, one of the best (and fastest) pools in the world can actually swim laps in the gutters (if they let you). They are huge. As with the depth of a pool, good gutters help to decrease water turbulence. Note: gutters only work if the water level is at the right height. If the maintenance people have the water too high or too low, they don't work!
Where a deep pool reduces turbulence coming off the bottom of the pool, the the gutters reduce the turbulence at the surface, which is arguably more important, since swimming is mostly done on the surface. As waves go into the gutter, they get swallowed up and do not bounce back into the race area. The gutter is a beautiful invention. Without them, the pool would be like the wave pool at the water park, especially during sprint events.
If the gutters aren't deep and/or wide, they will not be able to handle large wake and reflecting wake will result. And, since races go back and forth up the length of the pool, swimmers are constantly swimming against the current they created on the lap before. The more that current can be decreased the faster the swimmers will go.
Lane Lines. Good lane lines have the same effect as good gutters, except these cut down on the turbulence in the middle of the pool and between lanes and within lanes. Any swimmer that has swam in a pool with poor or no lane lines versus a pool with good lines can vehemently attest to this assertion.
Using a rope with buoys has no effect whatsoever. A good lane line should be taut and should have thousands of wave eating components. Usually these components consist of holes and fins. The key is having a lot of surface area to help break down the waves into much smaller waves without reflect them back into the swimming area. Most good pools use very expensive lane lines that are bigger than your standard lines, and they double them up in between each lane. Some times they also put them between the lane and the gutter. Triple lane lines used to be at many pools but are now considered illegal for most qualifying meets. There is no question, though that good lane lines help speed up a pool!
Lane Width. Very narrow lanes can not only hamper a swimmer's ability to swim freely and unobstructed, but can also create added turbulence between swimmers. The principle is simple, the further a wave travels the smaller it gets. So, the closer together everyone is to each other the bigger the wake each one will experience as a direct result of the other swimmers.
Lane lines that don't give swimmers enough room can also get in the way of kicks and strokes. Breaststroke and backstroke are especially susceptible.
Walls. The type of material the walls are made of and the slick-ness of the walls can made a difference in the speed of a pool. If walls are slick as can happen with many materials, and/or give way a little, which can result from poor bulkheads or shoddy workmanship, turns will be slower.
Blocks. The height, pitch, platform space, and grip all can drastically affect how well swimmers start. Put a set of IUPUI blocks at your local pool and you are bound to see times in that pool drop. The blocks at that pool have huge stable platforms which make you feel like you wouldn't fall off in a tornado. The pitch is not too steep and not too flat. The height is perfect and the grip you get on the platforms allow for aggressive starts. No question, good blocks lower times on the average.
Lighting. Physically, good lighting helps swimmers sight turns. Lines on the bottom of the pool and crosses at the turns are often difficult to see from afar, causing swimmers to misjudge the approach into turns.
Mentally, dim lighting does not help the motivation. Bright, well-lit pools give swimmers an optimistic, motivated feeling and in our opinions, help swims. Call it crazy, but we firmly believe it. Also, take a look at the fastest pools in the world--none are dimly lit.
Intangibles. Despite all of our good points, most veteran swimmers will have their own reasons--some legitimate, some superstitious, and some just plain cooky as to why some pools are faster then others. Often, if a swimmer has kicked butt at a particular pool, he or she will deem the pool to be fast and will continue to swim fast there time and time again--even if few others perform well there. In this case, the fast-ness of the pool is probably purely mental. But, that is also a large factor is what makes some pools faster than others. Our advice to competitive swimmers is to try to believe that all pools are fast for you. We also (more realistically) advise all swimmers to go out of their way to swim at a renowned really fast pool, shaved and tapered, at least once a year--even if it is just after a big meet or after the end of the season. You may be surprised at how big of a difference it can make!