Biofilm in water reservoir

Water analysis, treatment, and mineral recipes for optimum taste and equipment health.

#1: Post by elkayem »

I am approaching five months ownership of my new Bianca. This morning, I peered down into my water reservoir and discovered it is coated with a slimy white biofilm. It is thick enough to use as a nice hand cream, and it looks like the coating extends down into the tube running into my machine. Of course the reservoir is going straight into the dishwasher, but it got me wondering whether there is any concern here, or if I just need to be more vigilant about cleaning the reservoir. I'm not too concerned about health impacts, as I'm sure the boilers kill off the bacteria. My concern is more about damage to my new shiny machine. Is this biofilm normal? Any reason for concern?

A few more details... I strictly use Crystal Geyser water from Weed, CA. After convincing myself this is safe, non-scaling water, I opted not to use the tank filter (though maybe I should rethink this).



#2: Post by Smo »

Nothing wrong.
After 3 months I got a pink bloom. And in the resin filter too. I used bottled soft water. Now I use distilled water (I think it's sterile) + NaHCO3 - R Pavlis water.

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#3: Post by Nunas »

Biofilm in the reservoir is a petri dish of complex bacteria, many of which are a definite hazard to human health. That's the bad news. The good news is that heat kills the bacteria. So, there is little real hazard. However, biofilm left to grow in water systems, as you've discovered, can become a gooey mess. In industrial systems, this is serious enough to clog valves, strainers and the like. You can never 'get rid' of it, but you can control it by periodically filling your reservoir with a dilute vinegar solution, letting it stand for fifteen minutes or so, then rinsing it out. Once every few weeks should suffice. Incidentally, we have firsthand experience with the hazards of biofilm. We bought a couple of ultrasonic humidifiers last winter. They did a great job of keeping the humidity up. But we got terribly sick with pneumonia-like symptoms after a while. Our error was assuming that we would not have to clean them very often because we fed the machines with distilled water instead of tap water. Big mistake! :oops:


#4: Post by Smo »

The tank is easy to clean with a cloth and soap.
And distilled water, hopefully free of bacteria and fungi.


#5: Post by Smo »

Nunas wrote:We bought a couple of ultrasonic humidifiers last winter. They did a great job of keeping the humidity up. But we got terribly sick with pneumonia-like symptoms after a while.
Water has nothing to do with it covid-19.

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#6: Post by Nunas » replying to Smo »

Nope, we thought it might be and got tested; we were both negative. It was definitely the biofilm. We know this because we had a warm spell in the winter and shut down the humidifiers. The symptoms gradually went away, but I did not realize it was due to shutting off the humidifiers. However, when the weather turned colder, and we restarted them, we were instantly sick again. Anyway, back to the coffee, we now soak our reservoir about once a month with a bit of vinegar, as part of our normal monthly cleaning routine, and have very little to no apparent biofilm between cleanings.


#7: Post by Bluenoser »

I actually found a blackish film in my teflon tube of my no-burn wand. It was also some biofilm, I am assuming. I removed the tube for other reasons.. I may have biofilm in my, now, 'burn' wand.. but I can at least scrub it with a brush..

elkayem (original poster)

#8: Post by elkayem (original poster) »

Please tell me more about this vinegar treatment! My reservoir is in the dishwasher right now, but the tube at the reservoir interface on the machine side is stuffed with this icky gooey white slime, and I need it gone. So, what vinegar to water ratio should I be running through my machine, and how long do I let it soak before flushing it out? How does this even happen with bottled spring waster?

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#9: Post by Nunas »

I use half and half vinegar/water; it's also a mild descaling solution. The only issue with putting that in the machine is it takes a lot of rinsing to get the smell/taste out. You can also use bleach, but not in the machine, just the reservoir. I used that on my humidifier reservoir at a ratio of one teaspoon per gallon. Again, not in the machine. I never thought to put the reservoir in the dishwasher and I don't know if mine is dishwasher-safe. But if it is, that's gotta do it. As for how long to unclog a pipe in the machine, your guess is as good as mine. I do know that many years ago my dad used to fix small appliances, including coffee makers. Some were so clogged up he left the vinegar solution in overnight. You might check the destruction manual for your machine, though. I know that Breville recommends a vinegar solution for at least some of their machines, but other manufacturers might contra-indicate.

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#10: Post by Nunas »

The bleach solution is quite mild on second thought, so I wonder if one can run it through the machine. It would certainly kill all the bugs. I wonder if anyone here knows. As with vinegar, you'd certainly have to give it a good rinse. Another thing I was thinking of is the thickness of the biofilm...more like bio-slime. Perhaps you need to blow out or mechanically clean critical tubes/pipes in the water path.