Hot Water Might Disinfect Sinks Better Than Chlorine

The often deadly and contagious pathogens lurking in sinks and drains in hospitals may soon find themselves in hot water if the research being conducted by Emilie Bédard, PhD, keeps coming up with findings unveiled yesterday at the the annual conference of the Society for Healthcare Epidemiology of America (SHEA). Bédard is an assistant professor in the department of civil, geological and mining engineering at Polytechnique Montréal. Her study compares the tradition disinfectant for hospital sinks—chlorine—against very hot water. She found that the hot water (about 90°C) was anywhere from 100 to 1000 times more effective in getting rid of pathogens than chlorine. Bédard, who ran her tests at the MontrealChildren’s Hospital, explains to Infection Control Today® how the hot water method can be used in the real world.

Infection Control Today®:Would you explain how you conducted your study and what you found?

Emilie Bédard, PhD: Yes, it would be my pleasure to do that. So maybe just on how this study came about. We had some suspicions of sink drains being the source of pathogens in an intensive care unit. So, as you said in the introduction, we went with the common solution. We put chlorine in the sink drains, thinking we would reduce the load of bacteria that’s present in the drain. Although we had a doubt, so we measured it. We measured the bacteria two days after and seven days after disinfection, and we realized that less than a week after the disinfection, we were back to initial concentration of bacteria in the drain. We went back to the drawing board looked at other options and found an interesting study where they had installed a valve drain on the drainpipe to make sure that the disinfecting solution could stay longer in contact with the

Emilie Bédard, PhD:

surfaces of the drainpipe. And in parallel, we had also observed in another study that in sinks where hot water had higher temperatures at the faucet, we had less contamination within the drain. We decided to combine those two ideas and to go with an approach where we would pour hot water in the drainpipes with a valve so that we could ensure that the hot water would stay in contact with the surface of the pipe drain and maintain a better disinfection capacity. And so, in parallel to that we thought maybe that’s why chlorine didn’t work. As we poured it down the drain, it just went through and didn’t have enough contact time with the surface. We repeated the experiment with chlorine as well. We would pour chlorine into the drainpipe. But this time close the valve to make sure it would stay there for the duration which was 30 minutes for both the hot water and chlorine.

ICT®: And how hot did the hot water have to be?

Bédard: The hot water was initially close to boiling points. It was around 95 degrees Celsius. So that’s the initial temperature when we poured it down the drain. And then after a half hour, there was some heat loss through the pipe. We were down to about 60 degrees Celsius after a half hour.

ICT®: Who at the hospital coordinated this with you? What departments did you work with?

Bédard: We worked in collaboration with infection prevention, environmental services, and the pediatric unit; so intensive care unit. We had a multi-disciplinary team to make sure that we would look at all aspects of this approach. And it’s interesting that you mentioned that, because we also have the team that looks after the infrastructure—so the hot water system. And after a few weeks of conducting the study, we noticed that it was not working as well as the previous weeks after our disinfection with hot water. And the water in the drain was at lower temperature after half an hour. And as we brought it back to the team, we realized that there was some construction going on in the surrounding area with fans that have been installed which was cooling down the drain. The reason why I mentioned that is the temperature that you maintain within the drain for half an hour is important. If you go to lower temperatures, then it’s not as effective.

ICT®: And you got some pretty amazing results in terms of how much how much better the hot water worked compared to chlorine.

Bédard: Yes, it was 100 to 1000 times higher reduction [of the bacterial load] with hot water compared to chlorine in the study that we conducted. And yes, so that was working better.

ICT®: Did that surprised you?

Bédard: Not really, because…. In drains there is a thick, what we call a biofilm. A thick structure of bacteria and organic polymers that forms on the surface. And when you put chlorine and the chlorine needs doesn’t reach the bottom of this thick layer of bacteria, and organic matter. With the hot water, what happens especially because we were working with metal pipes, the temperature is really high, and it’s going to help disintegrate this biofilm that’s present on the surfaces of their pipes.

ICT®: And it seems like a fairly inexpensive method.

Bédard: Hot water is pretty cheap. Chlorine will react with the organic matter that’s present in the drain. And there will be some odors and some fumes that will be in the surrounding environment so that the advantage of the hot water is you don’t get that exposure with the hot water.

ICT®: And in further research will you look at how this could actually be applied to the real world? Will there be stations set up in hospitals where any health care provider can get the hot water? Would it be done in a systematic way? I think you said that it would have to be done weekly?

Bédard: What we’ve done with the preliminary results … we did a weekly disinfection. Now we’re working on how to optimize. Could we do it less frequently and have the same kind of results? Could we play on the time of contact? We went with a half hour disinfection. Could we do 20 minutes, and we’d have the same results? We’re looking at that. And we also need to think that you don’t necessarily want everybody and anybody to be able to do it because you need to activate or close down the drain valves. And if that’s done and not reopened, you can have some issues with water overflowing from the drain. You would want to integrate it into a cleaning routine or a routine where there’s a dedicated or identified staff that would take care of that, for example.

ICT®: Do you think that the plastic pipes could handle it?

Bédard: Well, actually what I do at home…. I have some problems with drainpipes that tend to block now and then. And when that happens, I put it to the hotter temperature—the hot water directly from the faucet into the drain—and I let it flow until I get a better drainage in my sink. And that works. And I have plastic pipes at home. I think that that’s why we need to work on the optimization of this approach. There might be other ways to do it without necessarily having to pour boiling water down the drain. But we need to experiment with that.

ICT®: I know that in many hospitals, infection preventionists oversee environmental service teams, or at least the two departments work very closely together. I’m sure they’ll be interested in your study. Is there anything I forgot to ask you that you think might be pertinent and that they should know about?

Bédard: I guess the last thing I maybe want to add is that you know it might look like more work or additional work. That’s why we’re trying to work on this to see how it can be part of their cleaning routine of a room, for example. Or try to integrate it so that it doesn’t add additional work. And that in the end it has a positive impact because we reduce the risk of infection from the sink drains to the patient or through the staff using the sink.

This interview has been edited for clarity and length.