Motorhome waste tank smells

Smelly Motorhome Waste Tank

Sosta motorhome parking in Italy

Smelly Motorhome Waste Tank

How is it that every time you drive off into the sunset, the freshly disinfected waste tank soon smells like rotten eggs? Well, if you’re also one of those long-suffering people, then maybe this is the read for you! Because finally we’ve hopefully found a solution to the smelly motorhome waste tank problem.

Yes, I know, how have we managed that I hear you ask?

Over the years we have tried every conceivable product to clean those tanks and nothing has solved the problem. Even a change of motorhome hadn’t helped the mystery of the smelly whiff’s lingering through the van, despite having numerous vans over a couple of decades!

Of course, those waste pipes and tanks are fresh as a daisy before leaving home, but after a few weeks on the road, those smells begin in earnest. On top of that, the heat of Summer in faraway shores really exasperates the problem as that waste water heats up too.

Soaking in Milton – Smelly motorhome waste tank

So, how do we clean the tanks? Ever since buying our fist van in 1989, we’ve sterilised the water pipes and tanks with a diluted Milton solution. This is usually twice a year or just before going away.

Milton is of of course a baby bottle sterilising fluid, so if it’s good enough for ‘Baby’, it’s good enough for us. This we pour down each waste outlet, for example, the shower tray, bathroom and kitchen sink before leaving it to soak overnight.

Next, is a thorough rinse through with a full tank of fresh water. Basically, involving opening each tap and letting the water flow into the waste tank. When the fresh tank runs out of water, we then open the waste to get rid of the Milton solution in the waste tank.

Now, this is all very well and good if we’re at home where we can easily get under the van and have the time to flush everything through. However, it’s not so easy in the heat, dust and dirt of a roadside dump area abroad. After all, even the best official dumps can still be quite unpleasant!

So, although the tanks are super fresh after a good rinse though with Milton solution, it doesn’t last long. This means, within a few weeks of travels, especially in hot weather, those stomach-churning smells soon return with a vengeance.

Disinfecting, Bleach and Elbow Grease

Once we realised the problem would never go away, we took a bottle of Milton in the motorhome with us.

Sometimes it’s difficult to buy the equivalent to Milton abroad, hence taking a bottle. Also, when using Aires, it’s not easy spending time at a dump cleaning out the waste system properly.

As many of you will know, there’s often a queue for water without the problem not being able to leave it to soak.

So, in recent years we tried a few other methods, such as pouring diluted disinfectant down the sinks and shower when we’re emptying the waste at the dump area.

We then open the fresh water taps in an attempt to flush things out, whilst at the same time filling the fresh tank and emptying the waste. Basically giving everything a good rinse through but not leaving it to soak.

Other things we’ve tried range from diluted bleach to product specific van waste tank cleaners. As well as Nigel on his hands, knees or back, lying on the ground beneath the van with a hose pipe in the waste tank!

This is not a pleasant experience! If you’ve been to the dump drain on an Aire you’ll know what I mean.

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Waste tanks below the bench seat in the Sprinter

The Smells Kept Coming Back – Smelly Motorhome Waste Tank

Well, you can’t say we haven’t tried. Unfortunately, after a few days the horrid smelly motorhome waste tank is back. So, we thought we’d resign ourselves to always doing some sort of cleansing process every few times we emptied the waste.

This had gone on for years, decades in fact and in each motorhome we had.

Even size or location didn’t matter. From the big A-Class Carthago, where the waste tank and pipes were fitted into a double floor to our current La Strada campervan, which has an external waste tank. Design held no barrier to the smells that kept coming back to haunt us.

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The Sprinter shower area

Hiring a Campervan without a Smelly Waste Tank

Then something strange happened!

Over the past few years, we hired campervan’s from the same company for trips of several months to Australia and New Zealand. Strangely enough, neither had a smelly waste tank, but was that just chance or was there something different going on?

It wasn’t until we came to buy our own van in New Zealand that the light bulb moment hit. Fortunately for us, we’d got friendly with the most incredibly talented guy, who also happened to build the campervan’s for the company that we’d hired from.

He’d kindly offered to help us with our own campervan conversion. Not only loaning us use of his tools, but also his yard, as well as providing various items of kit for the build. When it came to the waste tank, one thing he instructed us to do was to make sure it had a vent.

The Simple Solution To a Smell Waste Tank

My goodness, after all the year’s of a smelly motorhome waste tank, was a simple vent outlet the answer to the problem?

Over in New Zealand, we were able to buy our waste tank complete with a vent hole. Then Nigel fitted both the fresh and waste water tanks inside the van.

All Nigel had to do was to connect a vent hose. This he fitted to the pre-drilled hole in the tank, which then went up about half a meter to prevent leakage. It then dropped back down before coming out through a hole in the van floor, which Nigel had drilled.

The actual vent hose isn’t seen from outside as it is underneath the van itself. All we had to do was hope this would be the answer to our prayers!

Sure enough after several months of travels in the finished self-build campervan, we happily reported no smells! This is despite extremes of heat and continuous use – so similar conditions to travels in Europe.

smelly motorhome waste tanks
Fitting water tanks, notice the vent hose at the back

Fitting a Vent Hose on our Sprinter Waste Tank

Thank goodness, we’d hopefully found a solution to the smelly motorhome waste tank problem.

Now all we had to do was sort out a vent hose on our Sprinter campervan in the UK.

So, without further ado, Nigel got out his tools and slipped under the Sprinter to drill a small hole in our waste tank.

He then fitted a piece of vent hose into the hole. About half a meter in length, this vent hose simply now dispels any smells out underneath the van.

At last, we are hopefully smell-free. So, is the only aroma now sweeping through the van the smell of wild flowers?

Have we Cured our Smelly Motorhome Waste?

So it’s now 2 years since we’ve added a vent to our waste tank. Does it work, are those smells a long forgotten memory?

Unfortunately the answer is No! However, what we have found out is that our waste tank can never fully empty. That’s simply because there’s a lip around the inside of the waste tank which is lower than the drain hole.

When we look inside the tank from beneath the motorhome, this traps food residue and grime. These in turn will eventually begin fester as bacteria takes over and the smells rise up through the waste pipes and then the plug holes.

The only way we can potentially cure this is to re-locate the waste outlet in the tank. Hopefully we’ll get round to doing this sometime soon.

In the meantime, the only way to flush this out is to carry on doing what we’ve done. So, lying on the ground beneath the tank, remove the large tank cap and flushing the tank out with a hose pipe.

We’ll still clean and flush out all the pipes with a Milton solution or dedicated product. As for smells in the motorhome waste tank we know from our tanks in Australia and New Zealand that smell-free is possible.

So, here’s to the next step and the re-location of that waste outlet. Here’s hoping it’s the final piece of the puzzle.

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How Nigel fitted a vent hose on our Sprinter campervan


  1. We’ve never cleaned out with the old Coke trick, simply because it’s always seemed a bit too much of a sweet attraction to little insect pests! Wouldn’t like to take a chance on a trail of hungry Ants, wasps or cockroaches through the pipes and tank but no doubt it does give a jolly good clean…just like dropping a two pence piece in a glass of Coke..sparkling!!

  2. If you’ve not tried it, half a dozen bottles of cheap supermarket coke is a really easy and effective way to clean waste tanks. Incidentally, it’s not good to ever use bleach to clean plastic tanks as it’s corrosive to plastic. It won’t destroy it in one go, but can do serious damage.

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