Pool Plant Operators Guide

This Pool Plant Operator Guide is intended to be a valuable reference for the Pool Plant Operator looking after commercial swimming pools, spa pools, hydrotherapy pools etc. It is continually being added to and updated with the latest industry best practice. If there is a particular topic that you would like to be included in the guide, please let us know.

The Management of Commercial Swimming Pools


If a swimming pool is operating as a business (as opposed to a swimming pool in a domestic property, for the sole use of family/friends etc.), there are certain legal duties that must be complied with. Some of the main pieces of legislation that apply to commercial swimming pools are:

  1. The Health and Safety at Work Act 1974
  2. The Management of Health and Safety at Work Regulations 1999
  3. The Control of Substances Hazardous to Health Regulations 2002
  4. The Confined Spaces Regulations 1997
  5. The Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 2013
  6. The Construction (Design and Management) Regulations 2015

You can read more about how some of this legislation applies to commercial swimming pools in our in-depth article.

Pool Safety Operating Procedures

Swimming pool operators need to compile a set of documented procedures that set out how the facility is to operate under normal circumstances and how reasonably foreseeable emergencies should be responded to. The documents are referred to as the Normal Operating Procedures (NOP’s) and Emergency Action Plans (EAP’s). They are collectively known as the Pool Safety Operating Procedures (PSOP’s).

Pollution in Swimming Pools

Swimming pools are affected by three types of pollution:

  1. Physical (non-dissolvable)
  2. Chemical (dissolvable)
  3. Biological (alive)

Learn more about these sources of pollution here.

Swimming pool operators will need to think about and document how they will deal with these different types of pollution and respond to scenarios such as blood and vomit contamination and faecal contamination.

They will also need to consider the appropriate response to microbiological and/or chemical outbreak incidents.


In most commercial swimming pools, the primary method for killing germs is to use chlorine-based disinfectants. These substances release chlorine into the swimming pool water to kill various types of biological pollutants such as:

  1. Algae
  2. Fungus
  3. Viruses
  4. Bacteria

An undesirable side-effect of the chlorination process is the build-up of substances known as chloramines, which are a combination of chlorine and ammonia (the ammonia is itself a by-product of chemical pollution such as urine and sweat).

These chloramines are known as combined chlorine, whereas chlorine that has not yet combined with ammonia is known as free chlorine. Together, they are known as total chlorine.

Read more about free, combined and total chlorine here.

Swimming pool operators need to regularly monitor and record the levels of:

  1. Free Chlorine
  2. Combined Chlorine
  3. Total Chlorine

This is done using specialist pool testing equipment and these test should be carried out by trained Pool Plant Operators.

Read more about these swimming pool tests here.

Controlling the pH

The pH value of swimming pool water is essential to effective disinfection. The pH value is a measure of how acidic or basic a solution is.

The pH scale ranges from 0 – 14, with 7 being neutral (neither acidic or basic), values higher than 7 are basic, with values lower than 7 being acidic.

The ideal pH range for swimming pool is between 7.2 – 7.6. The problem is that most chlorine-based disinfectants used in the UK are highly basic, meaning that they have high pH values.

The two main chlorine-based disinfectants used in swimming pools in the UK and their pH values are:

  • Calcium Hypochlorite (pH of 11)
  • Sodium Hypochlorite (pH of 13)

The use of either of these disinfectants will cause the swimming pool water pH level to increase dramatically, well above the recommended range. In order to correct this, highly acidic substances (with low pH values) are used to keep the pH level of the swimming pool water within the recommended range. 

These substances are known within pool plant operations as pH reducers and there are four main chemicals that are used:

  • Carbon Dioxide
  • Sodium Bisulphate
  • Sulphuric Acid
  • Hydrochloric Acid

Filtration and Coagulation


Filtration is an important element of effective pool water treatment. The basic principle is that the untreated water is passed through a filtering medium (such as a bed of sand). The water can pass through the gaps between the grains of sand (called ‘pores’), but anything larger than the pore size is trapped within the filtering medium.

This is known as straining. There are two other processes happening within the filter, adsorption and sedimentation.

Read more about how swimming pool filters work here.


Commercial swimming pool filters do a good job of removing much of the suspended pollution from the swimming pool water, but only if they are operating in conjunction with a process known as coagulation.

Coagulation is a process whereby very small (microscopic) particulates are ‘stuck together’ (coagulated) using a substance such as poly aluminium chloride, to form larger clumps of particulates known in pool plant operations as ‘flocs’.

Read more about how coagulation works here.



How do swimming pool pumps workSwimming pool water is constantly circulated around a closed-loop circuit so that it can be filtered, heated and chemically treated before being recirculated back into the pool.

The job of moving the water around is that of the circulation pump(s). Most circulation pumps work via centrifugal action. An outer casing encloses an impeller that when rotating, causes water to be drawn in via vacuum suction. On the other side of the impeller, the water is under pressure and thus gets forced along the pipework. The pumps need to be primed (i.e. flooded with water) at all times in order for this to happen.

Read more about how swimming pool pumps work.

Turnover Rate

The swimming pool pumps need to be able to provide an adequate rate of circulation. This is so the pool water can go through the treatment process within a certain timeframe. This is referred to as the swimming pool turnover rate.

Different types of pool have different recommended turnover rates. The recommended turnover rate for a standard 25m swimming pool is 2.5 – 3 hours. 

Read more about swimming pool turnover here.