Grey Water Tank Inside Fresh Water Tank

I know, I know, this could be the craziest idea I have ever had! A grey water tank inside a freshwater tank how will that work?

We have all concluded that letting grey water trickle from the bottom of your VW T5 in a car park, can cause some poor reactions from people. Understandably, their first thought will be that it is effluent running from the van. It’s not, honestly, it’s dishwater. I don’t think that’s much better, to be honest. Grease can be a hazard in a car park.

If you are on site then most contain their grey water by placing a grey water tank under the van but when you are out and about, washing your hands, rinsing your coffee cup then unless you have a purpose-built grey water tank, it’s going to end up on the floor.

The Crazy Idea

Purpose-built grey water tanks in campervans are few and far between. That could be a lot of space taken up for essentially, something you really don’t need to carry.

In walks my crazy idea and guess what, it works! Has anyone taken apart one of those boxes of wine? The type where you get a giant silver pillow if you blow it up?

Here is where the concept is born! what if you put a large bag inside your freshwater carrier? could you then feed the grey water into it? The theory is semi-sound. What I mean is there are a few problems that I will talk about later.

How I Put It Together

I currently have a 10-litre fresh water carrier inside the T5. It has a large opening like the image on the right. This is essential for this idea.

Purchase a 10-litre w a ter bag. Cut a hole in the top of your freshwater carrier, roughly the size of the top of the water bag you have just bought. It’s better to go slightly smaller with your hole and that way it will be a snug fit.

Push the bag through the wide neck of your freshwater carrier so the bag is inside your carrier. Manoeuvre the bag spout through the hole you have cut.

Time to feed in your grey water pipe. Here’s a photo of what you should have.

a bag inside a freshwater tank acting as a grey water tank — water tank with a bag inside for a grey water tank

How It Works

Turn on the tap in the campervan. Water flows into the sink. The water then flows down the plughole and into the same container it came out of. The only difference is, the grey water is contained inside that water bag you fitted. This idea means that you only need one tank for fresh and grey water. Can you imagine such a system being built into campervans of the future? The space-saving is tremendous.

Are There Any Problems With This system?

Oh yes!

Possible problem number 1

My main fear would be the bag splitting and you not knowing. This would allow contaminated grey water to flow into your fresh water. This has never happened, but it could. The bags are really thick. there isn’t much chance of them splitting. I employ a safeguard where I put some strong-smelling disinfectant into the grey water tank so if any waste was to seep then your freshwater would suddenly adopt a sweet bouquet aroma.

Possible problem number 2

What if you didn’t use any fresh water and someone decided to empty a 2-litre bottle of cola down the sink? Well, this has happened and I can assure you that it seems that if there isn’t enough room in the grey waste bag then the grey water stops in the sink. That’s all well and good but if you then try to remove the grey water pipe to empty the carrier then it’s going to get messy. In this situation, the only solution is to put a saucepan or something under the freshwaterr tap. turn the tap on and watch the water from the sink slowly disappear. Don’t throw the saucepan water down the sink or you’ll end up at square one. Throw the saucepan water in the car park and you are back where you started!

My Conclusion

I’m never entirely comfortable with my grey water waste tank inside my freshwater tank. I’m not comfortable with the fresh water tank full stop. We don’t drink the water, it’s generally used for washing up or washing hands. I tend to use one of those 10-litre water bags for cooking because we do most of our cooking outside. It works for us and has solved the problem of wastewater. Maybe it could work for you. It’s great when your freshwater runs out and you can empty your grey water at the same time as filling your fresh!

If you like reading about water, read about our solar hot tub!