‘Blood flow’ in pools

Surface Water Removal

FROM THE POOL DECK with Vincent Munyeza

The surface water of the pool is where the highest concentration of contamination exists. Windborne debris, algae spores, bather body discharge and bather oils all collect at the surface. The pool’s disinfectant level is usually lowest at the surface. It is at the surface that the swimmer may swallow water. In addition, the swimmer’s nose, ears, and eyes have the greatest exposure to water at the surface.
Water may be removed from the surface throughout the entire perimeter of the pool or through selected point removal locations. Perimeter removal is through gutters, while point removal is through a box-like device called a skimmer.
Gutters
Gutters are trough like designs that work on the principle of surface tension removal during periods of pool non-use. The water level must be carefully controlled to no more than ¼ inch (6mm) above the lip of the gutter.
Surface debris and contamination are quickly removed from the pool and filtered or oxidised.
During periods of use, bather action creates a wave motion or a rolling effect. The surface water is trapped in the gutter and removed for processing.
There are several types of gutter designs. Older pools have what is called a scum gutter. This is a rather narrow gutter that can be recessed or partially open. The volume capacity of a scum gutter is very low and it may be difficult to achieve a 50 percent circulation draw through these older devices.
Surge gutters have a much larger capacity and are usually recessed. Both surge and scum gutters require frequent maintenance to prevent the build up of oils and debris that can contribute to the growth of algae.
Scum and surge gutters must be monitored by the pool lifeguard staff. Young or inexperienced swimmers can use these gutters as a hand-hold device. They are able to ‘wall walk’ down the pool to depths that are over their heads.
When they release their grip, these bathers can then panic when they realise their predicament and a drowning can occur.
Surge gutters are highly effective at removing large quantities of water for filtration and chemical processing.
They can be designed for wave suppression in competition pools and provide for easy maintenance access by having removable top plates
Rim flow gutters are one-foot wide and generally have two-inch slope from the water-edge tile to the back where the outlet drains are located.
There is little or no storage capacity in these gutters for bather load surge. It is easy to flood this type of gutter, which results in loss of skimming action under heavy bather loading.
Rim flow gutters are perimeter gutters that are more typically found on recreational pools. An integral parts of the rim-flow system is the grating.
The grating acts as a skimmer catching large debris from entering the filter system.
Since swimmers come in direct contact with the grating in a rim-flow system, the grating should have tamper proof fasteners holding it in place.
ENJOY YOUR POOL.