TABLE 4.
Parameter | Value for hot water heaters
|
Value for distal sites
|
||||
---|---|---|---|---|---|---|
CL phase | MC phase | P valuea | CL phase | MC phase | P value | |
Total chlorine detectable, no. (%) | 72 (75.8) | 77 (81.0) | 1.0 | 70 (76.1) | 77 (81.9) | 0.21 |
Free chlorine detectable, no. (%) | 59 (61.5) | 0 (0) | <0.0001 | 60 (63.8) | 0 (0) | <0.0001 |
MC detectable, no. (%) | 0 (0) | 85 (88.5) | <0.0001 | 0 (0) | 87 (92.6) | <0.0001 |
Temp categoryb | ||||||
<26°C | 4 (4.2) | 2 (2.1) | 0.61c | 2 (2.2) | 1 (1.1) | 0.54c |
26-42°C | 35 (36.5) | 39 (40.6) | 28 (30.8) | 35 (37.2) | ||
>42°C | 57 (59.4) | 55 (57.3) | 61 (67.0) | 58 (61.7) | ||
Mean temp (°C) | 43.6 | 44.1 | 0.72d | 44.1 | 43.5 | 0.57d |
Mean pH | 7.6 | 7.7 | 0.05d | 7.7 | 7.7 | 0.19d |
Mean conductivity (μS/cm) | 533.7 | 503.8 | 0.12d | 518.7 | 498.7 | 0.07d |
No. of sample locations with Legionella | 9 (9.4) | 4 (4.2) | 0.062 | 13 (13.8) | 4 (4.3) | 0.004 |
No. of sample locations with amoebae | 2 (2.0) | 2 (2.1) | 1.0 | 11 (11.7) | 14 (14.9) | 0.25 |
P value comparing the value for CL phase to the value for MC phase by McNemar's test unless otherwise indicated.
Categories indicate temperatures favorable (26 to 42°C) and unfavorable (<26°C and >42°C) for Legionella growth.
By Fisher's exact test.
By t test.