Yes. They are the only practical way of cooling water below the ambient dry bulb temperature in most industries. They are of lower capital cost, take up less space and use less power than alternative forms of cooling.

Legionnaires' disease is caused by a bacteria found in mains water that can thrive in the environment of a cooling tower and is then spread as aerosol droplets which are breathed in.

A cooling tower designed, installed and operated in accordance with Health and Safety guidelines need not present a risk.

The tower design must comply with Health and Safety Commission guidelines L8. Features such as high efficiency eliminators, graded basetank with underside drain, adequate access to internals and enclosed basetank to prevent entry of direct sunlight should be incorporated.

Coated steels are the most economic, but are prone to corrosion and water chemistry must be closely controlled to avoid damage of coatings.

Stainless steel offers increased operating life, but is attacked by the halogen group of chemicals that include chlorine and bromine, two treatments commonly used for cooling system sterilisation.

Plastics are of a similar cost to stainless steel but are inert to attack from water treatment and sterilising chemicals, and if suitably constructed are extremely robust and can offer an unlimited operating life. They also tend to be easier to clean.

Coated and stainless steel towers are normally built in panels, with internal flanges bolted together, and sealant material in all joints. At the cheaper end of the market overlapping panels fixed with self tapping screws are common. Each joint is a potential leak, the more joints, the higher the risk. Internally flanged panels with a multitude of bolts provide landings for contaminants and make cleaning difficult.

Ideally casings should be manufactured in one piece with joints kept to a minimum. This type of construction is most likely to be found in moulded plastic cooling tower casings. If site aesthetics are important plastic casings normally offer cleaner lines than their steel counterparts.

Gravity flow systems require to be maintained completely level. Any sagging or move from the horizontal can lead to the situation where, for example, 75% of the water flow is presented to 25% of the tower. They operate at low velocities and any suspended solids can easily settle out leading to fouling and again poor distribution of water.

Most modern cooling towers incorporate spray distribution systems. They do add to the pump head, but as most will require less than 0.35 bar, it is not normally significant relative to that for the total system. They operate at higher velocities than gravity systems and hence are less prone to fouling.

In forced draught design the fan is at low level, takes in ambient air and "pushes" it through the cooling tower. With induced draught design the fan handles saturated air, pulling through the tower and exhausting to atmosphere.

The forced draught design offers better access to the fan set (as it is at low level) and to tower internals (clear access via the top of the tower). The fan set is outwith the saturated atmosphere with reduced risk of down time due to motor failure. Direct sunlight entering the basetank can lead to biological growth. The basetank of the forced draught tower is enclosed, preventing the entry of direct sunlight that can lead to biological growth.

1. Register it with your local Authority. Ring the Environmental Health Dept. at your Local Council and they will send you details. Most councils only require basic information on a one page form.
2. Obtain a copy of Health and Safety Commission guidelines L8 and operate and maintain the tower as recommended.
3. Contact a reputable water treatment company to set up a treatment regime.