Can you dump grey water on the ground?

In this blog post, we will answer the following question: Can you dump grey water on the ground? We will discuss the rules for getting rid of, reusing and recycling greywater.

Can you dump grey water on the ground?

In the US, you cannot dump grey water on the ground. It is illegal to dump grey water anywhere else except in a designated city sewer connection. 

Grey waters are those that originate in the shower, sink, and toilet. They are stored in the lower part of the motorhome in special tanks, and they are emptied by means of a valve or a tap. 

If we want to avoid bad smells, we will take into account the following aspects when dumping grey water:

  • Use liquids specially designed for this purpose, which have a disinfectant aroma and also dilute waste.
  • Cover the hatch that communicates the tank with the toilet bowl.
  • Put the caps on the batteries after emptying and if we are not going to use the motorhome for a while, we can add a small amount of bleach.

The tanks or cassettes that collect the sewage have a rotating tube through which they are discharged into the corresponding drain, and which must be connected to a septic tank or the sewer. For cleaning, it is advisable to have a running water tap nearby, different from the clean water tap.

Although there are different possibilities for its evacuation, a simple drain, a PVC drain or a hole in the same grey water grate or in a separate box in the vicinity of a tap is enough. 

Given the characteristics of sewage in terms of odour and presence of solid waste, the place of evacuation should have a suitably adapted cover or grid, especially in those places with elevated temperatures during the summer. In the campsites and motorhome service areas it is duly signposted.

How to empty the grey water tank

The process of emptying sewage is simple and does not have to be unpleasant. Once the motorhome has indicated the filling stop to us by means of red light, installed in the cassette, we will proceed to extract it. We close the lid that communicates the cup with the tank, and we can take it out of the motorhome by the handle or transported it by wheels.

We will remove the cap from the funnel and begin the emptying. Later we will fill the water tank up to half and rinse. We can put soapy bleach to clean it better. Once the cleaning is finished, we will start again with the process of filling the disinfectant liquid and it will be ready for new use.

In the event that the red light does not work or we have passed waste, we will open the compartment where the cassette is and we will empty part of the waste into a bucket through the funnel. We will clean the compartment again and dispose of the water from the bucket in the area authorized for this use. In the same way, we will do with the “potty” of the caravans.

There are three types of liquids you can use to avoid bad smells:

  1. The blue one; for the waste tank, is a powerful liquid for daily toilet use. It will prevent bad odours. The bottle has markings to indicate the appropriate amount to pour (normally one cap for every ten litres).
  1. The pink one is not essential, it combines effectiveness and freshness. In toilets with a cistern, you can pour this liquid into the water, so that when you pull the cistern, it remains impregnated with this aroma at the same time as it disinfects.
  1. The green one biologically boosts the decomposition of toilet waste.

Although if a soft paper is used, it can be thrown into the toilet, we recommend not throwing paper into the toilet, so as not to complicate the decomposition process and if you want to avoid the smell of disinfectant, many travellers recommend adding a small plug of fabric softener along with the liquid.

In addition, we will not forget to add approximately a litre or a litre and a half of water once the liquid has been put in. With these recommendations, we will be able to keep the water tanks of our motorhome in perfect condition and without bad odours.

How to avoid bad smells in the motorhome

Currently, there is a wide range of products on the market that will eliminate bad odours from our motorhome. We tell you which ones you can use:

Aqua San: is for the clean water tank and serves to make the water drinkable.

Tank Freshener: it is designed for the grey water tank. Over time the tank ends up giving off an odour because the waste will end up going to the tank. It is more frequently used in caravans.

Cassette Tank Cleaner: This is for the toilet tank. When there are bad smells, we pour the product with very hot water, and the smell will be removed.

How to reuse and recycle gray water?

It is obviously impossible, and dangerous, to reuse wastewater without adequate treatment to clean it up. And their recycling is first of all imperative: have a double piping network: one properly connected to the public network to transport drinking water, the other reserved for recycled water.

The latter must imperatively be in a closed circuit and without any interconnection with the first network, at the risk of contaminating your drinking water. Recycling wastewater is thus easier if it is considered and implemented during the construction of a single-family house, even if it remains possible during the renovation.

On the practical side, the most natural method is based on the principle of phyto-purification, as for an ecological individual sanitation system. 

Several basins are then necessary to ensure proper cleaning of the wastewater: a pre-treatment basin to eliminate the largest waste by filtration (pozzolana, sand, etc.), a settling basin and a final basin planted with aquatic plants ( reeds, sedges, miscanthus, and many others) to finish filtering and cleaning up the water.

Other devices, more or less sophisticated and complex to implement, are also emerging, such as the one designed and marketed by a plumber from France. The invention itself is very simple: a water tank placed under the shower or the bathtub and equipped with a filter to retain hair and hair collects the wastewater and redistributes it in the toilet.

More expensive, there are also recycling units intended to collect not only the wastewater coming from the shower and the bathtub, but also from the washing machine or the sink, to redistribute it, again, in the toilets after filtration.

Our advice for the reuse of recycled gray water

To avoid any health risk, it is essential to take certain measures to secure and facilitate the water decontamination process:

  • limit the storage of recycled water over time in order to avoid the proliferation of bacteria;
  • favour organic cleaning products, free of toxic products and in particular, avoid bleach;
  • • also prefer natural and biodegradable soaps;
  • • avoid spraying the recycled water, which causes the diffusion of microparticles that can be inhaled.

To sum up, never lose sight of the fact that recycled greywater remains unfit for consumption, and for greater safety, avoid using any products that you would not put directly on your plantations.


Finally, each water distribution point must be perfectly identified using clear signage (labelling, pictograms, bright colours) in order to eliminate any risk of confusion between drinking water and recycled water. The same goes for any storage tanks, which must imperatively be labelled “non-potable water”.

Ecological and economical, the recycling of household wastewater undoubtedly has a bright future ahead and tends to develop around the world. We can bet that the many countries (Australia, United States, Japan, Israel, etc.) to authorize, or even organize, the recovery of greywater will pave the way for the generalization of this practice and that it will soon become the standard for any type of home!

If you have any comments or questions on the content, please let us know

FAQ on Can you dump grey water on the ground?

How to filter your gray water?

To filter grey water from the house and avoid loading wastewater treatment plants, you can consider creating a natural ecosystem based on reeds and aquatic plants. The principle is simple: it consists of circulating the water through a succession of basins planted with different species.

How to use gray water?

The use of treated greywater, which consists of recovering and collecting water from showers, bathtubs, sinks, washing machines, and possibly the kitchen, and then using it after treatment, is not authorized in France for domestic uses.

Where to throw wastewater?

Wastewater of domestic origin coming from our toilets, our bathrooms or our kitchens is therefore collected, as the case may be, by the unit network or by the “wastewater” network and normally transported, outside the periods of heavy rain, towards the wastewater treatment plant.


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