I'm so slow in the 25-meter freestyle they time me with a sundial. You know you're in trouble when the buzzards circle the pool.   But, a fast swimmer is something to behold and these competitive swimmers today are sleek.  New record times are set each year in each age group.  Splits of 0.01 second make the difference between qualifying and going home.  More and more school districts are getting into competitive swimming.

For these reasons, we pool designers are being asked to design 'fast' pools, pools where records can be set or at least where obstacles to good times can be removed. Here are some 'rules of thumb' you might want to consider if you are building a pool for speed.

Remove the doubt.  During construction I hope you checked your pool dimensions.  Inexperienced pool builders have been known to construct a pool out of square, the wrong length, bowed or all three.  Competitive pools require services of a surveyor who can certify not only the length of the pool sides but the length of each lane and the diagonal lengths across the pool to ensure 'squareness'.  While a shell a little too lengthy can be adjusted somewhat, it is awful difficult to stretch a pool.  NCAA, FINA, and USA Swimming all have tolerances on wall slant and course length.  If you want your swimmers to compete for records and want to host upper level meets, you will want to pay attention to these details when the pool is constructed. There can be no greater disappointment than to think you've broken the world record for the underwater inverted Australian frog kick only to find the course is five feet short!

Remove the surface turbulence as much as possible.  Surface turbulence not only sweeps over your mouth just when you  inhale but physically creates more impedance to  swimmer's forward progress. A freestyler's wake sweeps behind him or her in a familiar v-pattern and, if not suppressed,  can cross other wakes and the amplitude or height of the wake is multiplied.  If that isn't bad enough, the wake hits the sides of the pool and rebounds into the pool like an echo, creating even more waves until the pool  rocks to the extent it can swamp small boats or swimmers.

Experienced aquatic staffers are familiar with wave-quelling lane marker lines specifically designed to suppress the wake.  These lane markers are made up of individual disks (available in designer colors) with various assortments of holes and baffles to provide some interlocking between adjacent disks.  The weight of the lane marker plus the interlocking effect and shape of the disks is supposed to 'quell' the wake. 

Be aware that these disks come in at least two different sizes.  Larger disks are more effective in quelling surface turbulence than the smaller.  Also, these lines should be installed using  supertensioners on one end that keep the line taut. Supertensioners take up the inevitable slack created by swimmers holding onto and stretching the cable threaded through the disks.

Pool perimeter design is important. I was in the Caribbean this summer at a pool where the walls rose a a good three feet vertically above the water level.  Obviously, you won't encounter a competition pool with this extreme wall height because it makes starting block design a bit difficult. 

Nevertheless, some competition and training pools are still designed with vertical projections above water line of from four to twelve inches.  Vertical faces on the side of the pool create wave rebound which we've already decided creates pool rocking. 

'Fast' pools are now designed with roll-out style gutters flush with the water surface where the wake rolls over the grating without rebounding.  The benefits of this roll-out style are two-fold.  One, the rebound is negated but two, the surge in the pool is dissipated almost  instantly.  Most pools are operated at 'rim-flow' during meets. When the competitors hit the water, the volume of water each displaces must be taken out of the pool and returned between heats.  The surge (the displacement water) is stored either in a gutter or in a surge tank or both. 

You can also see that we are talking about full perimeter gutter overflow type pools and have not mentioned skimmer style pools with throat openings spread around the perimeter of the pool.  Skimmer pools will not usually be satisfactory for training or competition.  They require that objectionable vertical face we've already discussed AND they cannot remove water fast enough to a remote surge tank.

Remove the underwater turbulence.  The underwater turbulence in some competition pools is so great, pool managers are sometimes asked to turn off the circulation system.  Underwater turbulence comes from two general sources . . . the sidewall or floor inlets returning filtered water to the pool and from the swimmers turbulence. 

Floor inlets with diffusers are generally recommended for 'fast' pools because they disperse the currents rather evenly across the pool bottom.  Side wall inlets inject water only along the perimeter and create a slight but meaningful disadvantage for the swimmer unlucky enough to draw the outside lane.  Additional turbulence is fed from the end walls where, more than likely,  the inlets will not be spaced such that each lane receives equal jet resistance.  After all, the discharge velocity for a 15 gallon per minute-3/4" diameter jet is 10.9 feet per second.

The rebound turbulence from a swimmer creates a significant impediment to world record times.  The turbulence not only rebounds from the side walls but from the bottom of the pool.  Studies and experience have shown that depths of 7'-0" are necessary to minimize impedance from the floors.  The depths should be reasonably constant dropping gradually to a maindrain without sudden drop-offs such as diving wells.  And, in fairness, each swimmer should swim generally in the same depths of water.  In other words, make the contours (or lines of equal depth) run perpendicular to the swim course. 

To reduce the rebound from the underwater sidewalls,  pools can be designed with an additional outside lane wave quelling line and two extra feet of pool on each side.  Leaving off the added pool width is not a good place to try and save money.  Do not force the outside swimmer to swim against the pool wall without the lane line and the extra two feet of pool.

Remove the obvious.  Finally, when talking with your pool designer, watch out for the obvious.  You would probably be amazed at the number of competition pools with underwater light fixtures installed in the endwalls.  Now that can slow your time!   Remove above water impediments such as diving boards (and preferably diving stands), lifeguard stands, and ladders. 

If all of these suggestions don't bring a world record to your pool try getting faster swimmers.  Hey, I can only do so much!

Terry Brannon is a registered Texas professional engineer specializing in aquatic park and swimming pool design since 1977.