The grey water tank in the motorhome: what it is, how it works and where to empty it
— And what exactly is the grey water tank?
It is one of the most frequently asked questions we hear before handing over a motorhome.
And that is completely understandable. When someone goes on a motorhome trip for the first time, everything feels new: where to fill the fresh water, how to use the toilet, how the heating works, and where the water goes after showering or washing the dishes.
Therefore, before each handover, we show where the grey water tank is, how to open the drain valve, and where it can be emptied safely.
In this article we have gathered the answers to the questions our customers ask us the most.
What is the grey water tank?
The grey water tank is a container located under the floor of the motorhome. It collects all domestic water already used, coming from the shower, personal washing, or washing dishes.
In our motorhomes, the tank capacity is 120 litres.
Only water from the kitchen sink, the washbasin and the shower goes into this tank. The toilet has its own system with an independent cassette, so these two circuits are not connected to each other.
If you are curious to know how many days your water, battery and gas can last during the trip, we also recommend reading our article about the range of the motorhome.
Why is it called ‘grey water’?
Grey water is normal water that has already been used in the shower, bathroom or when washing dishes. It contains traces of soap, shampoo, grease and other household waste, so it is no longer considered clean water.
Waste from the toilet goes into a completely separate system: the toilet cassette. That is why grey water and black water never mix.
How do I know when the tank is full?
Our motorhomes have a fuel gauge that shows how full the tank is.
But there is also a simple reference.
The fresh water tank has a capacity of approximately 140 litres, and the grey water tank holds 120 litres. So if the fresh water is running low, it’s probably time to find somewhere to empty the tank.
In our experience, the greywater tank usually lasts between 2 and 4 days for two people. It all depends on how often you have a shower, wash up and cook.
Where is the grey water tank?
The tank itself is located beneath the floor of the motorhome.
The drain valve, on the other hand, may be located in different places depending on the model.
In most of our motorhomes, it is located roughly in the centre of the vehicle, next to the sliding door, beneath the kitchen area.
On some models, the outlet is closer to the rear.
That is why, during handover, we always show exactly where the drain valve is located on every vehicle.
When we first started renting out motorhomes, we realised that many customers simply didn’t know where to look for one. After several such incidents, we decided to always include this as a mandatory part of the handover.
How do you empty the greywater tank?
In practice, it's much simpler than it looks.
In most cases, all you need to do is press a button on the control panel: the valve opens automatically.
If, for any reason, this method cannot be used, the valve can also be opened manually.
After that, all you have to do is wait for the water to drain out completely. It usually only takes a few minutes.
Where can grey water be discharged?
Grey water must only be discharged at designated points.
For example:
- campsites
- Campervan site
- motorhome service areas
- many modern petrol stations that have a service area for motorhomes
When travelling, we usually locate these spots in advance using apps like Park4Night or Campercontact. This helps with planning the stop and avoids searching for a dump point at the last minute.
Always comply with local regulations. In Spain and in most European countries, greywater must only be discharged at designated points.
Do I need to use any special products?
Generally speaking, if you empty the tank every day or every other day, there’s no need to use any special products.
But in summer, especially if you’re going to be staying in the same place for several days, it’s best to add a product specifically designed for greywater tanks. It helps prevent unpleasant odours and keeps the tank clean for longer.
Our advice, from experience
Almost everyone taking their first motorhome trip tries to push the tank «to the limit».
It looks like, if there is still space, we can carry on without any trouble.
In practice, it is better to do exactly the opposite.
If you come across a campsite, a motorhome area or a service point for motorhomes along the way, it’s easier to stop and empty your waste tanks there and then.
It only takes a few minutes, and that way you avoid having to look for an emptying point with the tank nearly full, or dealing with bad odours in the middle of the heat.
Some tips before your trip
Before your first trip, it is worth bearing in mind a few simple rules.
- Do not wait for the tank to fill up completely.
- Check the water level indicator regularly.
- If you are going to make a long stop, use a specific product for grey water tanks.
- When collecting the motorhome, ask where the drain valve is on your specific model.
- After emptying, always check that the valve has been properly closed.
If you are preparing yourself for your first motorhome trip, we also recommend reading this article. And to avoid the most common mistakes, take a look at the article about the most common mistakes in a first rental.
If you would like to know more about the equipment of our vehicles, please check the section «Equipment of our motorhomes«.
Conclusion
After the first trip, maintaining the grey water tank becomes as routine as refuelling the car. The important thing is to understand how it works just once.
If you are planning a trip around Spain, on the website of LSR365 you will find not only useful articles about motorhome travel, but also tips based on our own experience renting and in daily contact with our customers.
If you are already choosing a vehicle for your trip, you can check out the entire fleet at LSR365 motorhome catalogue, and the rental conditions on the page of motorhome rental in Alicante.