Legionella in thermostatic shower valvesan exploratory field study

J. Van Hoof (ISSO) L.M. Hornstra (KWR)O.W.W. Nuijten (ISSO) P.W.J.J. van der Wielen (KWR)W.G. van der Schee (TVVL) E. Van der Blom (Uneto-VNI)

High-Priority-installations require routine analysis on legionella Even with regular analysis contamination is frequently reported•High numbers of legionella are reported thermostatic shower valves (TSV’s)•Contaminations appears often persistent

Objective of the study:•Investigate TSV’s in the field on legionella•Determine if TSV’s cause the growth of legionella by themselves

Why this study?

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ApproachFirst step:Select locations with a persistent legionella history during the last two years.

The field study consisted of:• Sampling the water of the TSV on three places• Demounting the TSV for research in the laboratory• Sampling the hot and cold water supply • Measure the temperature of the hot and cold water supply• Fill in a questionnaire with data on the:o Ambient temperatureo Frequency of use of the TSVo Water installation (history, maintenance)

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Investigation of the TSVCross section type A

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1. Outlet shower hose (not visible)2. Cold water inlet

4. Hot water inlet

5. Mix water outlet3. Mixing chamber

6. Rubbers and other parts

Investigation of the TSVCross section type B

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4. Hot water inlet 6. Rubbers and other parts

Autopsy

Demounting of a TSV prior to taking the swab samples

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Autopsy

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Sampling of the water

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Tap and water samples•Analyse on Legionella•According NEN 6265:2007•Inlet warm only < 55 °C

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Inlet cold Inlet warm

The TSV outlet mixed water

InvestigationSeptember 2012 until May 2013 at 5 locationsTotal 10 TSV’s were sampled

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TSV number Location Legionella history1 1 Hotel Yes

2 1 Hotel Yes

3 2 Hotel No

4 3 Health Yes

5 3 Health Yes

6 4 Health Yes

7 4 Health Yes

8 4 Health Yes

9 5 Health Yes

10 5 Health Yes14002

Legionella (cfu/l)

10

TSV number

Location TSV mix TSV cold TSV warm Autopsy

1 1 Hotel -

2 1 Hotel 1.400

3 2 Hotel -

4 3 Health -

5 3 Health -

6 4 Health -

7 4 Health 1.800

8 4 Health -

9 5 Health -

10 5 Health 10014002

Legionella (cfu/l)

11

TSV number

Location TSV mix TSV cold TSV warm Autopsy

1 1 Hotel - 11.000

2 1 Hotel 1.400 -

3 2 Hotel - -

4 3 Health - -

5 3 Health - -

6 4 Health - 330

7 4 Health 1.800 -

8 4 Health - 6.600

9 5 Health - 100

10 5 Health 100 90014002

Legionella (cfu/l)

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TSV number

Location TSV mix TSV cold TSV warm Autopsy

1 1 Hotel - 11.000 > 55 °C

2 1 Hotel 1.400 - > 55 °C

3 2 Hotel - - > 55 °C

4 3 Health - - -

5 3 Health - - -

6 4 Health - 330 > 55 °C

7 4 Health 1.800 - > 55 °C

8 4 Health - 6.600 2.600

9 5 Health - 100 -

10 5 Health 100 900 -14002

Legionella (cfu/l)

13

TSV number

Location TSV mix TSV cold TSV warm Autopsy

1 1 Hotel - 11.000 > 55 °C -

2 1 Hotel 1.400 - > 55 °C +

3 2 Hotel - - > 55 °C -

4 3 Health - - - -

5 3 Health - - - -

6 4 Health - 330 > 55 °C +

7 4 Health 1.800 - > 55 °C +

8 4 Health - 6.600 2.600 +

9 5 Health - 100 - -

10 5 Health 100 900 - -14002

Legionella (cfu/l)

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TSV number

Location TSV mix TSV cold TSV warm Autopsy

1 1 Hotel - 11.000 > 55 °C -

2 1 Hotel 1.400 - > 55 °C +

3 2 Hotel - - > 55 °C -

4 3 Health - - - -

5 3 Health - - - -

6 4 Health - 330 > 55 °C +

7 4 Health 1.800 - > 55 °C +

8 4 Health - 6.600 2.600 +

9 5 Health - 100 - -

10 5 Health 100 900 - -

TSVTSV coldFalse negative

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Legionella in the TSV (cfu/l)

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5 TSV’s: collective swab; 5 TSV’s: separate swab

Swab TSV 2 TSV 61 exit chamber shower hose Inlet warm2 Inlet cold Inlet cold 13 Mixing chamber Inlet cold 24 Inlet warm Exit chamber of shower5 outlet Mixing chamber6 Rubbers en other parts Rubbers en other parts

TSV number

Swab 1

Swab 2 Swab 3 Swab 4 Swab 5 Swab 6 collective

2 - 25 - - - 36

6 750 900 4.500 900 1.800 18.000

7 11.000

8 150

Highest number on rubber (smallest surface)

Second highest number on inlet cold

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Rubber, biofilm and Legionella

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Rubber enhances the growth of bacteria. Rubber: •encourages high concentrations of biofilm on the surface•is probably a “hotspot” for legionella

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Conclusions

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• Legionella can settle inside TSV’s• TSV’s can play a role in exceeding the threshold limit (100 cfu/l)• The highest number of legionella was observed on rubber parts• Legionella was found inside two TSV’s, but not in water coming

from the tap. Legionella stays in the biofilm• At 50% of the cases legionella was found in cold water• At 50% of the cases the warm water supply did not exceed 55 °C• The control for legionella in water systems can be improved

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Recommendations

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• Design TSV’s without material that encourages the growth of bacteria (rubber)

• Identify exactly the influence from the shower hose in further research

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Legionella in thermostatic shower valvesan exploratory field study

J. Van Hoof (ISSO) L.M. Hornstra (KWR)O.W.W. Nuijten (ISSO) P.W.J.J. van der Wielen (KWR)W.G. van der Schee (TVVL) E. Van der Blom (Uneto-VNI)