Legionella Testing & Water Sampling of Spas & Fountains during Legionnaires’ Disease Outbreaks

The following presentation examines Legionella testing and water sampling of spas and fountains during Legionnaires’ disease outbreaks in the USA. The presentation looks at Legionella water sampling of spas, decorative fountains, sprinkler systems, eye wash safety stations, humidifiers and respiratory care equipment; together with the measurement of other water quality parameters. The video featured in this presentation is one by the US Centers for Disease Control and Prevention (CDC) that gives an introduction to environmental health and engineering measures for Legionnaires’ disease outbreak investigations in the USA.

Legionella Testing & Water Sampling of Spas & Fountains

This is the final video in a series addressing environmental aspects of legionellosis outbreak investigations. It will demonstrate the correct procedure for collecting water samples from spas and fountains for Legionella culture during a cluster or outbreak investigation, or when cases of disease may be associated with a facility.

Environmental Assessment & Sampling Plans

Conduct an Environmental assessment and make a sampling plan before collecting samples. This video should be used in conjunction with the written document CDC Sampling Procedure and Potential Sampling Sites.

Personal Safety & Protection during Water Sampling

Call ahead and instruct the facility to turn off but do not drain the spa. This will stop transmission in case it is the source, but allow samples to be collected later. In situations where indoor, aerosol-generating devices in enclosed spaces cannot be shut down, wearing a half face air purifying respirator equipped with an N95 filter may be appropriate.

Respirators must be used in accordance with a comprehensive respiratory protection program which includes fit testing, training and medical clearance ahead of their use. Facilities maintenance personnel should always provide access to maintenance areas like the spa equipment room and they should open filters.

Collecting Water Samples from a Spa

You should be prepared to collect several swabs from the jets and water line of the spa in addition to a bulk water sample. Run the tip of the swab firmly against the surface at the water line and inside the jets. Collect 3-5 millilitres of water from the spa into a 15 millilitre sterile plastic tube. Place one swab per tube into enough water to keep the swab tip moist during transport – snap the stem about 1 inch from the top of the tube.

Add a drop of 0.10 normal sodium thiosulfate solution to neutralize residual disinfectants. Tighten the top to prevent leakage. Then label each tube with a unique identifier. Record the type and location of the sample on a sample data sheet and place the tube onto a cooler.

If the spa is not drained collect a 1 litre bulk water sample in a sterile 1 litre bottle. If the spa is partially drained a swab tube may be used to collect the remaining water. If the spa has been completely drained ask facility maintenance personnel for access to the compensation tank – for collection of overflow water and take a bulk water sample from there.

Add 0.5 millilitres of a 0.1 normal sodium thiosulfate solution to neutralise residual disinfectants. Tighten the top to prevent leakage. Label the bottle with a unique identifier. Record the type and location of the sample on the sample data sheet and place it into the cooler. You also need to measure the water parameters. Remember it is possible for a spa to pass routine environmental health inspection and still harbour Legionella.

Measuring Other Spa Water Quality Parameters

Collect some water in a separate plastic bottle. Measure the spa water temperature. Make sure there is enough time for the thermometer to stabilize, measure pH by placing the paper strip inside the bottle. Compare the colours on the paper strip with the legend on the box.

You may also use a digital pH meter – it is best to use a pool test kit or digital colourimeter to measure residual disinfectant in spas. Spas may use other halogenic disinfectants such as bromine. Follow the test kid instructions for conversion, if the residual disinfectants levels exceed the maximum limit of the test kit; perform serial dilutions to bring the sample within the test kit’s range. If there is a very small amount of disinfectant in the spa use your potable water test kit. Record all data on the sample data sheet.

Collecting Samples from Spa Filters

It is very important to collect a filter sample from spas; the filter is usually located in a separate maintenance room. Gloves should be worn due to heavy organic loads typically found in filters and the abrasive or caustic nature of some filter filling material.

Sand, Cartridge, & Diatomaceous Earth Filters

There are 3 types of filter – sand, cartridge, and diatomaceous earth. The method for sample collection depends on the filter type. When sampling sand filters, collect some sand in a 1 litre bottle and enough water from the filter chamber to cover the sand.

If the spa has a cartridge filter cut a portion of the filter to fit inside a 1 litre bottle and add enough water from the filter chamber to cover it. If the spa uses a diatomaceous earth filter collect some water from the filter chamber into a sterile 1 litre bottle.  Use a sterile swab to scrape diatom powder from the grid. Make sure it is completely covered by at least 1 inch of water.

With each filter sample you take add 0.5 millilitres of 0.10 normal sodium thiosulfate solution to the sample to neutralise residual disinfectants – tighten the top to prevent leakage.

Label each bottle with a unique identifier, record the type and location of each sample on the sample data sheet and place it into the cooler. Note that collecting filter samples may disrupt the integrity of the filter, requiring maintenance service or replacement.

Collecting Water Samples from Fountains

As with spas call ahead to make sure the fountain is turned off but not drained, fountains and similar water features require biofilm and bulk water sampling as well as measuring water parameters. The procedure is the same as sampling spas with the exception that decorative fountains often do not use filters.

If there is a filter sample it the same way you would a spa filter. The number of swabs depends on size and the complexity of the feature. Swabs should be taken from the water line and any surfaces with noticeable biofilm accumulation.

Water Samples from Sprinkler Systems, Eye Wash Safety Stations, Humidifiers & Respiratory Care Equipment

Using available epidemiologic evidence and your knowledge of the ecology of Legionella you can determine whether additional samples are needed from devices like sprinkler systems, eye wash safety stations, humidifiers and respiratory care equipment. It is extremely important to make sure you collect, label, record and transport your samples accurately and carefully.

For more information please reference the written document CDC Sampling Procedure and Potential Sampling Sites.

Legionella Testing & Water Sampling Experts

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Further Reading…

More information about the CDC Legionella Environmental Assessment Form – Download … here →