The Ultimate Swimming Pool Quiz

A swimming pool actually floats in the ground water surrounding it. If the pool were to be emptied, the ground water pressure might push it out of the ground. Modern pools have a hydrostatic valve that allows ground water to flow in and equalize the pressure if necessary.

Above-ground pools are the cheapest to install and they are the simplest type of pool to build.

A vinyl-lined, in-ground pool is constructed by digging a hole in the ground, assembling a metal, plastic or wood frame and lining the structural wall with vinyl. Vinyl-lined pools are cheaper than other in-ground pools but are not as durable. The vinyl lining will need replacing approximately every 10 years.

There are usually two or more main drains in a pool and they are usually located at the lowest point of the pool, so that the surface of the pool floor slants towards them. Dirt and debris that sink will generally exit the pool through the main drains. Antivortex covers placed on the drains prevent hair or limbs getting caught in the plumbing and prevent a potentially dangerous vortex of water forming.

The drains that sit near the top of the pool walls and collect floating debris, such as leaves, suntan oil or hair, are called skimmers.

The only way the suction could be strong enough to hold someone against the a drain would be if only one drain were open. A properly designed pool will have multiple drains to spread the force of the suction between them. If one drain gets blocked, the system will pull water from the other drain, eliminating the suction force on the blocked drain.

The water pump is the heart of the pool. A typical system will have an electric motor spinning an impeller, which drives the water coming in from the drains through the filter and back out to the water inlets.

To prevent the pump becoming clogged with large debris, water flows through a metal strainer before it enters the pump.

Sand filters are often used in the pool pump. Gravity pulls the water down through the sand to the bottom of the filter where it exits through an outlet pipe, but the dirt and debris gets caught in the tiny sand particles.

Pressure gauges indicate when the blockage level inside is increasing due to a build-up of dirt and debris slowing down the flow of water through the filter. If the pressure gauge shows more pressure on the inlet pipe than the outlet pipe then you know that your filter needs to be cleaned.

To clean the filter you need to backwash it. By readjusting a number of valves, water is redirected from the pump up through the sand, dislodging dirt and debris and flowing out into the sewer system.

Some pool systems use a diatomaceous earth filter system. In these systems, the water passes through a filter grid coated with diatomaceous earth. Diatomaceous earth is a fine powder made from the fossilized remains of sea organisms.

By law, all the water in the pool must pass through the filter system over a certain period of time, usually between 30 minutes and six hours.

Pool water may be lost by evaporation, backwashing and water that splashes out of the pools or is carried out on people's bodies or bathing suits. The pump is connected to a municipal water line so the pool can be topped-up when necessary.

Bacteria thrive in water so it is important to maintain a good chemical balance to prevent bacteria from being able to grow in the pool. An imbalance of pool chemicals can also cause damage to the pool, irritation to skin and eyes and the water may become cloudy.

Chlorine is the most popular pool disinfectant. It is used in the form of a chemical compound, such as calcium hypochlorite or sodium hypochlorite. Chlorine reacts with water and creates various chemicals, one of which is the hypochlorous acid that kills bacteria and other pathogens.

Chlorine may come in liquid, powder or tablet form. Professionals may even use it in gas form. Pool experts recommend adding chlorine to the water just after the filtering process, but it can be added to the pool anywhere in the cycle.

Hypochlorous acid can combine with ammonia, found in urine, or with other substances and produce chloramines. Chloramines hinder the sanitizing process, since there is less free hypochlorous acid to kill germs, and it may irritate the skin and eyes. Chloramines are also responsible for the unpleasant odor sometimes smelt at pools, indicating that the pool is dirty.

The pool pH level affects the effectiveness of chlorine. Chlorine will dissipate quickly if the water is too acidic and an alkaline pool will hinder the effectiveness of chlorine at destroying pathogens.

Pool experts generally recommend a pH of between 7.2 and 7.8. To change the pH, simply add acids, such as sodium bisulfate, or alkalis, such as sodium carbonate or sodium bicarbonate, to the water.