A Brief Guide to Tanks

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Water tanks are something that most RV’ers take for granted especially the fresh water tank which is just about mandatory in any RV. However, many a contemporary rig these days comes with both a grey tank and a black tank.

Grey water tanks for sink and shower drainage have just about become standard fit in motorhomes and 5th wheelers but until recently far less common in caravans. However, that particular trend is changing with many upmarket caravans having grey tanks as standard and quite a few other manufacturers having them as an option.

Lastly, there’s the black tank used for toilet waste. That usually comes in the form of a cassette tank which is easily removable for emptying. Two manufacturers dominate this market, Thetford and Dometic and both usually supply 17 – 19 litre tanks. Larger motorhomes and 5th wheelers often have a fixed black tank.  Composting toilets are quite common in the marine market but they are only seen occasionally in the RV sector.

Being Self-contained

Self-contained is a term that is being used more commonly these days, in particular when referencing freedom camping. It essentially means that an RV can stay in an area without the need for any tank drainage which some campgrounds specifically require.

There are some places, like for instance sports ovals and council showgrounds, where a “sock” of waste rag is required to catch any solids whilst letting grey wastewater through. Some European manufacturers offer a roller tank for wastewater.  That is a portable grey tank that can be used to collect grey water and then wheeled away to a disposal point.

Tank Maintenance

Tank odours usually caused by dirty tanks can be a problem. Both grey and black water tanks should be cleaned (not just drained) regularly. Chemical treatment should always be added to black water tanks after every time of emptying. There are also chemical treatments available for grey water tanks which can be used from time to time as required or prior to long term storage.

Freshwater tanks aren’t immune from having bacterial type problems either, especially if the RV has been stored for an extended time. A good flush is usually the answer but there are also some manufacturers who supply a specially filtered drinking water tank.

There isn’t much maintenance required on toilet cassette tanks, apart from keeping them clean. However, for those that have rubber seals, they need to be clean and have the occasional spray of silicone lubricant (not petroleum based like Vaseline) to give a good service life.

Dump Points

Disposing of black and grey water can be done a dump point. These are usually found in caravan parks but there are a number of towns in Australia where a dump point is available in a central location. The Campervan and Motorhome Club of Australia (CMCA) has been very pro-active in the installation of many of these dump points and now there are more than 330 throughout Australia. These are free for anyone to use of course. Caravan park ones are usually for guest use or attract a usage fee if not staying in the park. Many RV’ers keep a supply of disposable gloves handy, particularly when draining the black water tank.

Designers of dump points don’t always understand the end user. Some RVs have low grey-water drainage valves and there seems to be an assumption that somehow or other, water will flow uphill. Others are fitted into locations that are difficult to get an RV into. Not that there are any books on the subject but dump point etiquette is quite simple – leave it as you would like to find it.

Keep on trucking

Like any RV feature, a bit of water tank maintenance and cleaning goes a long way and should result in healthy travel, long service life and getting around in an environmentally friendly way.


Tim van Duyl

Coming from marine publishing Tim now oversees Caravan World and Trade-a-Boat for the Adventures Group as their Senior Editor. With experience garnered from travelling the breadth and width of his home country New Zealand in all manner of ways, his mission is to see all Australia has to offer. Having already sampled Cape York, Murray-Sunset National Park, Wilsons Promontory and the bulk of Victoria’s West, he has plans to add to the small parts of WA and NT already seen. When not on the road you can find Tim passing time at lakes around Australia or in the high country camping with his close friends and family with the Murrindindi a popular spot.


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