HONG KONG'S SUB-TROPICAL CLIMATE is ideal for outdoor living and an increasing number of house-holds with gardens are buying swimming pools. A pool can become the focal point of family activity and entertaining and can add value to real estate. Pools come in plastic, fibreglass or concrete, of which the last is the most durable and adaptable. They are likely to last as long as the house itself, whereas pre-fabricated, above-ground, plastic or vinyl-lined pools can be taken with you if you move. Concrete pools offer most flexibility because they can be designed according to a home-owner's specifications and can make maximum use of awkward spaces. The pool can become an integral part of the design of a house. In contrast, says Dennis Lo, director of Century Pools (tel: 2602 8622), a pool with plastic lining will have a shorter lifespan owing to damage done by the sun's ultraviolet rays. Concrete pools can be made a variety of depths and shapes - kidney-shaped is the most popular in Hong Kong - and finished with plaster, mosaic or glass tiles in a range of colours. Finishes in aqua or a foggy blue, which gives the effect of mist on the water's surface, are in demand. Images of dolphins, fish or other decorative items can also be set into the concrete. There is a much wider choice of underwater lighting available for concrete pools and the water-filtration systems are more effective. Optional extras include the new Liquid Electronic Display (LED) underwater lighting systems offered by Group Eagle Enterprises (tel: 2571 5660), which do not generate heat like traditional bulbs. LED lights come in six colours - amber, yellow, red, blue, green and purple - and can be set to change colours. High labour costs mean concrete pools start at about $300,000, excluding lighting and heating, making them the most expensive. They are also the most time-consuming to construct at about a month. Above-ground, plastic or vinyl-lined pools are most popular with people renting homes and those who do not want a permanent fixture, as well as with those on a tighter budget or in a hurry to go swimming. Paradise Pools (tel: 2174 6842) sells above-ground pools in a range of materials, sizes, shapes and colours. The maximum depth is 1.2 metres. Plastic liners can come decorated with tile patterns or fish images, although this costs more. Underwater lighting is another option. Jimmy Ling, sales manager at Paradise Pools, says lighting fixtures in plastic pools operate at less than 24 volts. It is important to keep water in the pool year round to reduce the effects of sunlight on the plastic. A pool liner usually lasts three to five years but the outer structure, made of heavy duty PVC, should should last longer. Above-ground plastic pools of 18.5 to 46.4 square metres can cost $20,000 to $50,000. Prices include the filtration equipment and installation. Although Paradise Pools can supply fibreglass pools on request, they are not popular in Hong Kong, according to Ling. He says while they cost about 70 per cent of the price of concrete pools, they are limited in design and adaptability. Next week: installing a swimming pool.