We recently saw positive Legionella results from a mixer tap (that isn’t unusual we hear you say), however, the cold water feed showed no Legionella, the hot water feed showed no Legionella, but the mixer tap had very high results.
Why is this?
Well, there are several things that we know –
- No Thermal Protection After the TMV - After the TMV the water temperature is not high enough to kill biofilm or micro-organisms such as Pseudomonas or Legionella, so there is no effective thermal control.
- Biofilm favours plastic – PVC will attract around 100x the Legionella growth of copper – see http://www.wales.nhs.uk/sites3/Documents/254/2%20Biofilms.pdf. Plumbing componants are often plastic, these are at a higher risk to harbouring micro-organisms – below are a few nice electron microscope slides showing what hides in shower pipes and taps…..
- The more complicated the taps the more likely the occurrence of Legionella –here is what research found - “Although the high-tech faucets cut daily water consumption by well over half, Johns Hopkins researchers identified Legionella growing in 50 percent of cultured water samples from 20 electronic-eye faucets in or near patient rooms on three different inpatient units, but in only 15 percent of water cultures from 20 traditional, manual faucets in the same patient care areas. Weekly water culture results also showed half the amount of bacterial growth of any kind in the manual faucets than in the electronic models.” See http://www.hopkinsmedicine.org/news/media/releases/latest_hands_free_electronic_water_faucets_found_to_be_hindrance_not_help_in_hospital_infection_control
- The water use in specific faucets may be limited - this can cause low-flow, and thus stagnation and lack of flushing.
- Biofilm likes flow straighteners in taps – see Investigation of healthcare-acquired infections associated with Pseudomonas aeruginosa biofilms in taps in neonatal units in Northern Ireland. JT Walker et al. There are many other factors as well, but these few allow you to see that
- There is no effective microbial control past the TMVs
- The pipework and equipment past the TMV may actually prove to be at a higher risk of colonisation than the standard piping.
Great, so how do I control Legionella in my taps?
Well, you could install an Aquadron system and disinfect the whole water system, even beyond the TMV’s, all of the time…..
.....and you could do the following -
- Check for underused outlets and consider installing automatic flow solenoids.
- Assess water distribution system for non-metallic materials e.g. flexible hose.
- Assess water system for blind ends and dead legs.
- Consider disinfection of hot and cold water distribution system and the outlets.
- Ensure that the TMV providing the safe hot water is located as close to the tap / shower outlet as possible.
- Consider replacing contaminated taps with new taps.
The Aquadron is a water treatment system that treats all of the water all of the time using a non-hazardous, low-cost biocide that the Aquadron produces.