I. Introduction

A spa pool is a self-contained body of warm, agitated water designed for sitting or lying in and not for swimming or total body immersion. Spa pools contain water heated usually between 30°C - 40°C, which is filtered and chemically disinfected. It will have air/water massage jet circulation and can be sited indoors or outdoors. A spa pool is usually drained, cleaned or refilled after a number of bathers or a maximum period of time rather than after each bather.

Commercial spa pools should incorporate sand filters, although the principles of operation will be similar for other types of filtration systems for spa pools, including cartridge filters. Common terms for spa pools are hot spa, hot tub, whirlpool spa and portable spa.

Jacuzzi® is the registered trade name of a specific manufacturer and should not be mistaken for a generic name for spa pools.

II. Health & Safety

A Spa Pool is not necessarily drained, cleaned and refilled after each individual bather, but there are stringent recommendations that operators are advised to observe, to ensure the safe bacteriological, hygiene and health giving aspects of its use.

Spa Pools should not be considered as small swimming pools as there are significant differences between them. Spa Pools operate with lower water volumes, much higher bather to water ratios, high water temperatures, and aeration of the water. The combination of these factors produces ideal conditions for the presence of potentially harmful organisms. They also ensure the rapid dissipation of disinfectant residuals.

It is therefore important that operators follow a regime that ensures the necessary bacteriological and chemical standards are maintained. In practice, this may involve operating the Spa Pool in excess of the manufacturers recommendations.

Good practices do not come cheaply, and an input of resources in both staff time and finance will be needed to meet the high standards of operation identified. It is, however, likely that there will be benefits through customer loyalty and repeat visits.
Spa pools can be built in a variety of ways. In all cases, the pool structure, surface and liners can be damaged by poor water treatment. For example, undiluted chemicals inappropriately added to the pool can easily attack the surface and colour of the vinyl, or the tile grouting.

Privately-Owned & Domestic-Type spa Pools:

Spa pools or hot tubs installed in privately-owned properties and homes and are for the exclusive use of the owner, family and occasional guests, are not subject to health and safety at work legislation. The operational use of such systems does not therefore fall within the scope of this guidance of this web page.

Domestic Spa Pools Used As A Business Activity:

Domestic-type spa pools or hot tubs used as part of a business activity (eg in a holiday park) are subject to the general duties under the Health & Safety legislation. There is a legal requirement for these systems to be managed and controlled in proportion to the risk and the risk assessment should consider the type of pool and its use.

Domestic-type spa pools are typically used by a small groups of people at any one time and normally consist of a rigid or inflatable structure with freeboard and skimmer. The water should be changed after each rental/week, whichever is the shorter and disinfected using bromine or chlorine through the use of an inline disinfectant feeder.

Domestic-type spa pools are not suitable for medium or large-scale business use, or for commercial activity, as design features and systems for control are unlikely to be sufficient to cope with user demand and a commercial-type spa pool should then be used. These include installations where there is potential for a higher bather load and/or there is continuous bather use, or where several accommodation units have shared access to a spa pool, eg at a holiday park or large hotel.

Where the use of a commercial-type spa pool is not possible or practicable, a risk assessment should be undetaken to consider the bather load and take into account the control measures required to effectively manage the risk in this setting. After each period of hire, the spa pool should be completely drained, cleaned, refilled, disinfected and drained again. When stored, the spa pool should be dry, including the insides of the spa.

Units On Display:

There have been significant disease outbreaks associated with spa pools on display. When a domestic-type pool is on display at a showroom or exhibition, the pool should be displayed empty of water as there would be no intended bather use. However if it is filled, the risks posed to individuals who work with or pass in close proximity to the spa pool must be considered and must be treated and controlled.

Hot Tubs:

A hot tub is a small, purpose-built unit for indoor or outdoor use and is designed for sitting in. They should be filled with treated water, maintained at a temperature above 30°C, fitted with air jets and aerated. They are generally designed for a small number of discrete bathers where the water is not changed, drained or cleaned after every use. Hot tubs are not for swimming in and do not have a balance tank.

Whirlpool Baths

Whirlpool baths are designed for one or two bathers where the water is not treated, and are intended to be filled and emptied after each use. Whirlpool baths are usually fitted with water jets, which can be angled in use. In addition, there is usually an air track in the floor of the bath, powered by an air blower system and/or air may be introduced to the water jets. Whirlpool baths have the potential for similar problems to spa pools such as the formation of biofilms within the pipework system associated with the air and/or water booster jets, and should be regularly disinfected.

Natural Spa Pools

The concept of natural spa pools is that the water is untreated, but this in itself can pose potential health and safety implications. Natural spa pools must be managed to control the risk of exposure of bathers and others to infectious agents. This will usually require the natural spa pool to be managed in the same manner as any other commercial type spa pool.

Risk Assessment

All the factors outlined for these different types of pools must be considered as part of the risk assessment process. Design bather load is a key characteristic and should be considered as part of the risk assessment to achieve effective control. There are circumstances in which a domestic type hot tub would be unsuitable and a commercial type spa pool should be used. These include any settings where there is potential for a higher bather load and/or there is continuous bather use, or where several accommodation units have shared access to a spa pool (eg at a holiday park or large hotel). Where the use of a commercial type spa pool is not possible or practicable, the risk assessment must consider the bather load and take into account the characteristics of the spa pool and the control measures required to effectively manage the risk in this setting. After each period of hire, the spa pool should be completely drained, cleaned, refilled, disinfected and drained again.


The Pool Tank:

Spa pool tanks can be fabricated from a range of materials, the most common being acrylic, but they can also be formed from concrete, which is painted, tiled or in some cases lined with either a vinyl sheet material or laminated glass reinforced plastic skin.

Pool Surrounds:

The pool surround (whatever the surface) should be slip-resistant, flat and without any trip hazards to avoid injury to pool users. Cracked paving slabs, tiles or tarmac should be repaired as quickly as possible for safety reasons.

Pool Steps & Ladders:

Pool steps, access ladders and handrails should be fitted securely to the pool tank or surrounds, not freestanding. The step treads should also be secure and fitted with slip-resistant surface.

Spa Shells:

Because of the nature of the spa, the shell must be constructed in such a way to deal with high water temperatures, chemicals for disinfection and cleaning, high usage levels, cleaning and maintenance programmes. The shell must be impervious to all chemicals used in the vicinity of the spa, be easy to clean, surfaces should be slip resistant, and free from sharp edges and protrusions.

Balance Tank:

A balance tank is required to hold the water displaced by bathers entering the spa and before the water enters the filtration system. Balance tanks may be fitted with low-level alarms which automatically shut down the filtration system to prevent damage to it. The tank needs to be easily accessible for inspection and cleaning. One area of operation that is often neglected is the emptying of the balance tank. This needs to be carried out when the bathing numbers reach 50% of the volume of water in the spa pool assuming 80 litres per bather. The balance tank should be cleaned out and run to drain. Remember to clean the fittings as well, as bacteria could be present due to the high water temperatures.


Within the UK, it is the Health and Safety at Work Act 1974 that places a legal duty on pool operators to ensure a safe working environment and safe working practices.
They also have a Duty of Care to all those who use the facility, including those who are not lawfully entitled to use them such as trespassers. Should anyone be hurt or damaged as a result of non-compliance with the law, there will be an investigation which could lead to the prosecution of individuals and organisations, and the almost inevitable claim for compensation, for injuries or damages.
There are also several publications which have helped to interpret the requirements of the law, in relation to the operation of hydrotherapy pools.


The hydrotherapy pool industry has adopted Managing Health and Safety in Swimming Pools HSG179 and the Pool Water Treatment Advisory Group publication Swimming Pool Water Treatment and Quality Standards in Pools and Spas as being the key authoritative texts and it will be found that most normal operating procedures and emergency action plans for hydrotherapy pools are based upon them.

V. Spa Pool Consultancy and Design Services

Bluepools provides specialist hydrotherapy pool design and consultancy services where new premises can be designed or existing pools brought up to current standards.

Here are a few recent projects:


Hagley Spa