Best Practice for Cleaning A Grey Water Tank

Cleaning your grey water tank can be an inconvenience and hassle sometimes. But if not done properly can be harmful to the environment. As much as we just want to do a spot clean per se, we must keep in mind that we should be economically and socially responsible even in this simple practice. And, it’s a nice way to contribute to keeping the RV world running as we all want to, isn’t it?


What makes the best cleaning practice?


That is, to use the optimum cleaning recipe and being eco-friendly. Optimising the cleaning recipe involves 4 T’s – time, temperature, titration & turbulence. A perfect blend of these will give you maximum clean at minimal effort and time. Eco-friendly is using minimum-to-no hazardous chemicals to produce effluent at acceptable contaminant levels.

Most RV users can perform cleaning but not optimally, more so rarely apply eco-friendly practice, so in this post, I identified measures to make your grey water tank “clean and green”.


The Optimum Cleaning Recipe


Just because your grey water tank is a waste tank does not mean that it should be cleaned with water only. Every cleaning agent manufacturer uses the 4 T’s to determine the most effective and efficient cleaning recipe which defines their “Instructions for Use” – that is why it is important to obey such instructions when cleaning your grey water tank.


  1. Time

The cleaning agent needs sufficient contact time with the grey water so it can degrade and neutralise well the sludge, grime or muck – whatever you call it.


  1. Temperature

The temperature must be high enough to run the desired chemical reaction which separates the dirt, but heating your cleaning solution to 100°C is not necessary. There is a temperature range where cleaning agents act best.


  1. Titration

Too weak of a cleaning agent will of course not achieve your desired cleaning result. On the other hand, too strong a cleaning agent only unnecessarily contributes to harmful waste and is a waste of money.


  1. Turbulence

Chemical action alone is not sufficient. The addition of a good mechanical action makes the cleaning result a whole lot better, thus the need for turbulence. Some tips include:

    1. Going for a drive – ideal during the soaking periods of the Basic Cleaning Steps since it generates minimal turbulence only
    2. Using a spray ball – ideal in the filling and rinsing steps; you only have to attach it to the hose of your water supply and it’ll do the work for you; below are factors you must consider when using this tool – See what a spray ball looks like and where to purchase see here-
Small-sized – so it can fit through the narrow mouth of your tank Requires you to shell out a bit of extra cash Purchase the basic one – it’s sufficient for the typical grey water tank size
Can have a cleaning coverage of up to 360° Needs enough pressure from the water supply line Use a small portable booster pump


The Basic Cleaning Steps


The easiest way to go is to follow the instructions stated in the packaging of your chosen cleaning agent. If you don’t know any cleaners click here. However, if you plan to use DIY cleaning agents, here are the basic steps used in the cleaning industry:

  1. Empty the tank. Use a cloth at the mouth of the hose to filter any particulates.
  2. Pre-rinse with hot water (≥60°C) to soften and remove all debris. Flush after.
  3. Caustic wash
    • Prepare a 2 to 3% dilute caustic solution (e.g. baking soda) at ≥60°C.
    • Fill your tank with the solution to neutralise fats, oils and grease (FOG).
    • Soak for 10 minutes, with occasional scrubbing and/or stirring to promote turbulence.
    • Flush and rinse with ambient temperature water.
  4. Acid wash
    • Prepare a 1 to 1.5% dilute acid solution (e.g. vinegar) at ≥60°C. Slowly pour the acid into the water, NOT the other way around!
    • Fill your tank with the solution to neutralise the pH of any remaining caustic wash.
    • Soak for 10 minutes, with occasional scrubbing and/or stirring to promote turbulence.
  5. Rinse and flush your tank with ambient temperature water. You may apply a sanitiser after to completely kill the bacteria, but this is not required every time you clean your tank (sanitisers are strong chemical agents).


Important Notes:

  • Do not use too high temperatures if your tank is made of plastic.
  • Household vinegar has at most 4% acetic acid.
  • Concentration percentages may be based on weight or volume (there’s not much difference).


What is grey water by the way?


Waste water is generally classified into two types – black water and grey water.

  • Black water is the waste generated from toilets, urinals and closets.
  • Grey water is basically wastewater that is not black water, thus generated from other sources such as sinks, basins, showers, etc.

The treatment methods for black water and grey water are different, that is why they must be stored SEPARATELY.


How often should I clean my grey water tank?


A good rule of thumb is after every waste disposal. You may think, “Okay, then how often should I dispose of my grey water?” The key is to take note of the prevailing temperature during your trip because…

Grey water can be generally stored for 24 hours maximum before bacteria can grow and transform the grey water into black water which is harder to treat. However, this can drastically reduce to 4 hours during summer since bacteria thrives in higher temperatures.

Therefore, the minimum cleaning frequency you must do is every 4 hours in the hot summertime and every 24 hours in an ambient temperature environment – that is, 20°C to 25°C.

Your tank doesn’t need to be full before you dump.


What are the regulations regarding grey water disposal?


Each Australian state/territory has its own Environment Protection Agency arm which governs its disposal regulations. Offenders can and do get reported to these bodies if found to violate disposal regulations. These are their useful links:



Disposal regulations at parks and campsites vary by that specific park/campsite, but a common requirement is that RVs need to have waste tanks of sufficient size to contain the waste during the entire camping period.

Many park/campsites provide a disposal point for grey water. These facilities may be found at RV Dump Stations.

Where no disposal point is provided, these good practices must be observed:

  • Dispose grey water far from the campsite and water bodies.
  • Do NOT discharge on one tree only.
  • Dig a hole that can serve as your dumping point, and then cover back the hole after use.


What practices can I do before the trip?


Prevention is better than cure. So to spare yourself of having to do a tedious clean of your grey water tank, keep in mind these practical tips:

  1. Check your tank cleaning agent and household cleaning products
    • Go for eco-friendly or organic products. Look for eco-friendly certification logos in their packaging. Phosphate-based cleaners are a no-no.
    • See to it that there is sufficient cleaning agent and that it’s not expired. A cleaning agent’s potency is lost when expired and having long intervals between trips means RV users can miss this.
    • It must be suitable for the material of your grey water tank, instruments and discharge hose/pipe. Common tank/hose/pipe materials are stainless steel and food-grade plastics.
  2. Prepare your protective equipment for the cleaning, such as rubber gloves and waterproof footwear.
  3. Verify that the size of your grey tank matches that of your freshwater tank. If undersized, you might want to provide a tote container for a longer storage period. This is especially important if your trip destination has no disposal points.
  4. Minimise solid waste. Here’s how:
Avoid preparing oily and greasy food. If unavoidable, use vegetable oil since it does not easily solidify at low temperatures. Ensure that your fresh water supply is soft. You can determine this by checking if your skin feels soapy after a shower – if it does, then you should fit a filter on your fresh water supply line.
Wash/clean your food (especially your meats) and then store them in seal-tight containers.


What practices can I do during the trip?


  1. Remove any solid waste before it reaches your grey water tank – for example:
    • Leftover food from your utensils and cooking equipment, and
    • Strained materials from your kitchen sink, lavatory sink and shower drain.
  2. Take it easy on the shampoo, soap and detergents. Anything excessive is harmful.
  3. Maximise using the park’s or campsite’s facilities so you won’t have to do the washing or bathing in your RV.
  4. Do not remove or shove over the strainers of your sink and shower drain.
  5. Include the tank accessories (e.g. valves, sensors, etc.) and hose in your cleaning. Occasionally spray any rubber seal with silicone lubricant.


What practices can I do after the trip?


Definitely dispose of your grey water and clean your tank after each trip.

Drain all water from your RV when not in use. For our friends in the northern hemisphere especially during winter to prevent the pipe from exploding.


How to stop my grey water tank from smelling?


The main cause of this problem is bacterial growth, so the best treatment is to regularly dump your tank.

Adding sanitisation (once in a while) at the end of your cleaning step also helps.

If the odour persists, it may actually come from your pipes or grease trap. Thus, conduct the Basic Cleaning Steps, but running the fluids through the line instead of soaking.


Final Thoughts


All it takes to best clean your grey water tank is to:

  • Minimise the intake of solids,
  • Use eco-friendly cleaning agents as per manufacturer instructions, and
  • Do your due diligence

Happy cleaning!



For more information see the About Us page

Recent Posts