The Ultimate 2021 Grey Water Tank Cleaner Guide

Grey water holding tanks might not be the most fashionable accessory in your caravan, but they are a  necessity if you want freedom to explore more than just caravan parks when hitting the road.

Grey water tanks and proper disposal of the wastewater help you keep your caravan, RV or motorhome clean, free of smells and planet-friendly. 

If you plan on travelling across the country and to Australian national parks, this tank might actually be legally required. And while it’s not mandatory at regular campsites, it’s ethical and advisable to have one rather than draining grey water directly on the ground.

Types of Caravan Water Tanks

Caravan water tank

A caravan water tank is a fresh water supply for modern caravans, supplying clean and fresh water to your sinks and showers. There's another level to this, as there are three separate caravan water tanks, namely the freshwater tank, grey water tank and black water tank or cassette.

Freshwater tanks, as the name suggests, store clean water for your taps, toilet and shower. The water goes through associated water pumps, which can be electric or manual. Manual pumps can be either foot pumps or hand pumps. We have a written a separate article on "how to clean your fresh water tank".

A grey water tank receives dirty water from your kitchen sink, washing machine, bathroom sink and shower drain. 

A separate black water holding tank or cassette is where  waste water and waste from your toilet gets drained into. 

What Is Grey Water and When Is It a Problem?

Caravan adventure on the road

The definition of grey water is simple: It’s any domestic wastewater not coming from your portable toilet. This wastewater includes those from the sinks, shower and washing machines. Once grey water is mixed with toilet waste it’s now black water.

When you’re at home, it’s easy to get rid of grey water onto the garden or lawn, or divert wastewater somewhere your plumbing allows. Most houses in Australia are connected to sewer

But in a caravan or motorhome, that’s not the case. 

Grey water doesn’t stay grey for a long time. It will turn “black” within a half day or so, and even more quickly in warm, humid conditions. Owe it to bacteria that multiplies rapidly in hot and confined environments, a.k.a. merciless Australian summers. 

Organic material and bacteria can also get trapped in parts of the plumbing, leading to awful smells. Expect grey water gone bad to turn off the neighbours or anyone within close range once it makes its way out of the hose. 

The problem doesn’t end with bad odours and unsanitary conditions. Chemicals like soap and cleaning products may also harm the environment. 

Grey Water Tank: Proper Storage and Disposal

Caravan silhouette

As many campsites require that caravans stay self-contained, they should be able to store grey water adequately until they leave the area. In this case, grey water tanks comes in handy: built-in and integrated into the caravan plumbing. 

How grey water tanks work is simple: they often have a manually operated valve to divert the flow from the grey water outlet into the tank. Some owners retrofit a tank to the caravan, while others use an external counterpart. 

You’d be surprised at how some RVs use no more than a big plastic bottle to collect grey water.

Many older caravans do not come pre-installed with a grey water tank. Amid changing council regulations across the country, it’s common for caravanners and campers to have to install their own grey water tanks. There are usually three steps to do this:

  • Choose the right grey water tank for your caravan.
  • Install your grey water tank close to your plumbing fixtures, typically close to the shower and sink.
  • Mount the tank in an easy to reach location. Make sure your caravan grey water tank fittings are close by. You might need to install extra support bars or larger grey water holding tanks. Your grey water tank should come with manufacturer’s instructions outlining the installation process required for your specific grey water tank.

Parked caravan at campsite

Now comes an exciting part for caravanning nerds and enthusiasts like us: How to properly dispose of the contents of the grey water holding tank. 

Here are some ways that grey water is usually disposed of across different places and situations:

  • Stored grey water - Many caravan owners simply store the water until they reach a public dump point, or at least before it becomes black water.
  • Caravan parks - Most of these parks in Australia provide a grey water drain to direct the water using your outlet hose. This drain can be an open drain or a purpose-built drain. Other parks, however, simply ask visitors to direct their grey water onto the garden or grass nearby. It’s best to double check about proper disposal in these areas. 
  • Free camps - Rarely do these sites offer proper disposal systems for grey water, in which case it’s allowed to run onto the ground. Here, being kind and considerate of other campers in the vicinity counts a lot. 

Cleaning Up the Tank Walls and Other Tips

Caravan on camping trail

Here are some common-sense and not-so-common-sense techniques to clean your RV’s grey water tank. 

Pre-cleaning and cleaning phase

It’s important to watch what you flush. Dirt, food preparation wastes and other food waste, grease and the like can all stick to the sides of the tank.

Excess soap when hand washing or taking a shower can also be an issue, sticking to the sides and clogging up water tanks alongside other waste materials. This is a perfect recipe for nasty smells and hard-to-remove foam. 

Always empty your grey water tank, ensuring no leftovers get left behind. Do this particularly if you won’t be using the caravan for a while. Again, empty the tank only at designated or proper dump points. 

Get a specialised grey water tank cleaner

Not every product is fit to clean your grey water tank, so go for the right detergents and tank cleaners at your favourite camping or outdoor lifestyle store.

Detergent for cleaning

No special detergent?

Mix warm water with a dishwashing liquid, and then pour the mix into the grey water tank. Do this before the day of driving, where the will splash around and the mix will soak up the dirt lining the tank walls. Drain it after 24 to 48 hours. After emptying, flush out the tank with clean water. Repeat if necessary. 

Baking soda trick

Try a vinegar and bicarb soda solution

Every so often, try to flush the sink once in a while with vinegar, which can help with odour control. 

The secret sauce of grey water tank cleaning

We’re sharing a secret with you today on how we clean your own grey water tanks. It involves the EcoTraveller 4-in-1 multipurpose cleaner, which you can get online by itself or as part of a caravan cleaning starter bundle. 

4-in-1 Multipurpose Caravan Cleaner


This 4-in-1 caravan toilet and bathroom care concentrate is perhaps the only solution you’ll need for cleaning up your RV. The 4-in-1 product is considered one of the best portable toilet chemicals for 2021.

It’s a toilet bowl cleaner, flush rinse, tank cleaner and multipurpose bathroom cleaner in one. With its concentrated probiotic formula, it provides 10 times the value and suits your caravan and motorhome needs. 

How to use it for your tank

4-in-1 is a straightforward solution to clean grey water tanks and also your shower drain, kitchen sink and toilet basin. The 4in1 liquid contains probiotic bacteria which will remove dirty grease build up from your kitchen drain. This should be added on a regular basis to both the kitchen sink and shower drains.

Add it in concentrated form down each drain. We would also recommend emptying the tank.  Fill half with water add 200 ml of the 4-in-1 solution. 

Drive down to your next destination and allow the contents to swish around the tank. Empty it once you get to your destination and the job is pretty much done. 

More Tips for Your Grey Water Holding Tanks

Australian national park landscape

Grey water tanks help store your wastewater from the RV kitchen, shower and washing machine until you can safely and effectively dump it. They are a crucial part of your RV’s water system. 

If you’re yet to get one, bear in mind that there are several considerations to make. One is the weight; if the payload isn’t a concern, a big tank makes sense. Portable grey water tanks for caravans are also a sound option and offer good value. 

You might also wonder: How can I make less impact on the environment with my grey water? 

Well, it’s not nearly possible to convert grey water into potable water on your own, but there are steps you can take to lessen its impact on your surroundings. 

Here are a few simple tips and tricks:

Go septic-friendly in your caravan toilet chemicals

Probiotic-based bacteria solutions like 4-in-1 are biodegradable and don’t contain toxic chemicals to start with. This goes a long way in safety and eco-friendliness. This also makes disposal of the waste easier as it can be dumped almost anywhere.

Keep your grey water systems clean

Flush your grey water pipes after use and use friendly commercial cleaners regularly. 

Filter out food waste and solid matter

Dispose of food preparation wastes and other food wastes along with your regular trash. After eating, dry-wipe your plates and utensils with paper towels before washing them. 

Don’t use your caravan shower as a toilet

This might come across as obvious to many, but not to some. This will make dumping or draining  the waste easier.

Camper on the road

It’s still important to do your due diligence. Make sure your holding tank doesn’t get damaged by any commercial cleaner or product. Consult existing documentation on your grey water tank to be sure. 

If necessary, use a professional service to deep-clean your grey water system. Do proper research before seeking out an expert or going DIY.


Discover nifty tips and tricks to clean your caravan water tanks or today's well-loved portable toilet chemicals on the EcoTraveller blog.