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Posted 28 August 2019 - 07:56 PM

Hi there,

I am going through the process of determining an appropriate drain cleaning methodology including dosing and frequency of cleaning of the floor drains in the factory.

We have significant biofilm which showed no response to Hypochlorite or Enzyme based cleaners, we did however see good reduction using Hydrogen Peroxide.


My questions are as follows:

- Am I best to get a drain cleaning company in to get the drain closer to clean

- How do other places clean the drain, with a mechanical action

- We have an hourly water flush to keep the drains flowing - does anyone else dose a flush with a chemical - if so what?

- How often do folks who use Hydrogen Peroxide use it on a maintenance basis.


Thank you

Hank Major

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Posted 28 August 2019 - 08:26 PM

This has been discussed recently, but I feel like we couldn't resolve the issue completely: 




Biofilms are a tricky subject.  If I have time I'll do some research and post something.  


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Posted 04 September 2019 - 12:32 PM

I like to use peracetic acid as a sanitizer.  Sterilex also works well.


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Posted 04 September 2019 - 01:33 PM

Slightly OT but for a Product-compatible, wet Production scenario,, my experience has been that using (a few ppm) chlorinated process/cleaning water (continuous injection) significantly decreases the  microbiological background of the work environment surfaces, drains etc.

Kind Regards,



Hank Major

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Posted 04 September 2019 - 08:38 PM

The scientific literature says that every drain is a different ecosystem and that the species makeup of the microbial community within depends on many factors. They have a multitude of suggestions.


The material that the drain is made from is important, but it remains uncertain if any material is better or worse.  I personally think stainless steel would be best, but PVC is not a bad material or anything.


Biofilms will develop resistance to chlorine and quaternary ammonium cations (quats) over time.  This resistance is not an evolved resistance; the members of biofilm use all kinds of extracellular excretions to protect themselves.  This means that after a cleaning down to the bare metal or plastic pipe, the survivors will not be able to instantly recover the properties of the biofilm from their genetics.  The individuals in the biofilm are not adapted to chlorine and quats or anything else.


My take on biolfilm resistance is that they will eventually develop resistance to any sanitizer or combination of sanitizers.  One must include a mechanical cleaning component such as scouring or ultrasound.  Unfortunately, mechanical scrubbing has a tendency to produce an aerosol of live bacteria which will float up and away and settle all over the place.


Ultrasonic cleaning with a hot potassium hydroxide-based detergent solution is mentioned as successful in knocking back biofilms by 4 logs in 60 seconds. 


As people above mention, a continuous drip of chlorinated water works sometimes, peracetic acid works sometimes, and hydrogen peroxide works sometimes.


On the more experimental track, competitive exclusion with non-pathogenic species has been found to work. Soaking biofilms with Lactococcus lactis and Enterococcus durans has been shown to wipe out Listeria monocytogenes


Interestingly, the ambient humidity in the air in the drain plays an outsized role in keeping biofilms alive.  So if a drain is rarely used, one could cut off humidity to the biofilm above the waterline by pouring in a layer of mineral oil.  This also prevents sewer gases and odors from exiting the drain, and, who knows, might even keep the bacteria from aerosolizing and exiting the drain too.


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Posted 05 September 2019 - 10:41 AM

It depends on your set up, are you just talking about the drain "top" or any gulleys i.e. the bits exposed to the plant?  Or are you talking deeper within the drain?


If it's the latter, I'd question why you're going to extremes to get rid of the biofilm.  Unless it's severe, it's not going to jump out from a few metres down and back into your plant, unless the drain backs up.  If you have a backing up issue, it's that I'd sort out.


But there are great ways to clean drain gulleys / tops and any surface in general.  These are the ways I'd do it.


  • Clean the drain with dedicated cleaning equipment.  Yes it is on the floor but it's also often dirtier than the floor, you don't want to spread that crap around!
  • Remove any grids to clean.  Remove any gross debris then foam them or soak them in a dedicated trough and scrub clean.  Actually scrub them and do the same with any parts of the drain accessible, e.g. gulley or the top of the outfeed.
  • Allow contact time, rinse then disinfect with a oxidizing disinfectant e.g. peracetic or hypo.  Allow contact time, then rinse off.  Both hypo and peracetic are very readily deactivated by organic residues.  Unless you use slow dissolving tablets like you can with hypo, there is no purpose to leaving it on.  Then after rinsing it off I'd use a second disinfectant.  Because it's a drain in floor areas, I'd use quats.  They can cope with a bit of debris so have a longer term action.  You've also given a "double whammy" for any biofilm with two different modes of kill.  Works well on floors too.  Also consider how you apply the disinfectant.  A spray can be far more effective at getting it where you want and into nooks and crannies and adhering than bucketing it down (again same with floors.)

If you have got a backing up issue or blockage or want to get external drain cleaning companies in, be very wary that whatever they do will probably spread whatever contamination is in the drain everywhere.  They literally spray water jets into that drain producing aerosols galore.  We all have to use them from time to time but from bitter experience, empty the room first if you can, follow that two step disinfection procedure with all surfaces if you can and fog afterwards.

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