Help …My Camper Smells Bad

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Why does my motorhome smell?

Do you have a bad smell in your motorhome? How do you prevent condensation and damp? We’re here to help with this comprehensive guide to motorhome odours.

If your motorhome or campervan smells of any of the following, then you can fix the problem and prevent it from happening again.  Work out where the smell is coming from, or whether it’s a general all over smell. 

  1. Sewage
  2. Sulphur and rotten eggs
  3. Damp and musty
  4. Fishy
  5. Ammonia
  6. Unidentifiable

My motorhome smells of sewage


Sewer smells in a camper are likely to be an issue with either your motorhome toilet and its’ cassette (sometimes called a black water tank) or your grey waste tanks. Grey water or waste is any liquid waste that is not toilet waste and goes into a holding tank, or series of holding tanks underneath your habitation space.   Not all motorhomes have sink traps so sometimes the smell can come back up through the plug-hole.


  • If you think it’s the loo, then give your camper bathroom and loo a good clean.  Empty the cassette and clean with a specialist product like Elsan Deep Clean Cleaner.
  • If the odour is more general throughout your motorhome, then your grey water tank need to empty your grey tank at a suitable disposal point and flush out and clean your grey waste tank. Here’s how – access a hose with good pressure and literally get your arm as far into your waste or sewer tank as possible giving the hose a good spray around, whilst keeping the drain open. Allow the water to drain fully and then close the drain and fill the grey waste tank to around 20%. Add some specialist heavy duty tank treatment like Pro-Kleen Intense Waste Pipe and Tank Cleaner for Caravans and Motorhomes before taking a road trip along some (hopefully) mountainous and bendy roads to your next destination, so the whole lot sloshes around, before emptying on arrival. 
  • As a short-term measure, you could mix a cup of baking soda (half a cup to a pint) and pour down each drain.  It will eliminate the tank odour and makes an effective and quick motorhome waste tank cleaner.

How do I stop it happening again?

If the problem is with your cassette toilet then;

  • Fit a SOG system to your loo, this takes smells away by using fresh air via an electrical ventilation system, no chemicals required and your motorhome bathroom smells fresh!
  • The flush system on most motorhome loos will not cover the whole bowl with water unless you run the flush for at least 30 seconds; not the best use of your limited water!  Keep a spray bottle of water in the loo and use to to cover the bowl after use…this will dilute any residual urine and stop it breaking down so quickly, which is when it starts to smell.
  • Clean your loo every day, including all the surrounds.
  • Clean your cassette inside every time you empty it using a specialist product like Thetford Cassette Tank Cleaner.
  • If you use chemicals, make sure you are adding the correct ones and the right amount.
  • Use lightweight toilet paper that decomposes quickly.
  • Some people do not use their toilet to poo in, but I can confirm (after years of working in elderly care) that urine smells way more than poo! 

If the problem is with your grey waste tanks then;  

  • Scrape dishes and pans before washing to remove as much residue and food waste as possible.
  • If you’re on site, utilise their washing-up facilities.
  • Try using eco-friendly soaps and liquids manufactured without chemicals which won’t contaminate your water systems.
  • Use a strainer basket on your plugholes.
  • Where possible, empty your grey waste tank daily.
  • Flush your tank and pipes through and clean regularly.

The smell is of sulphur or rotten eggs


This is either your grey waste tanks or your leisure batteries

Check your batteries first;  if the smell is located in your garage or wherever your leisure batteries are fitted and they are fizzing (you’ll know if they are!) then your battery has ‘boiled’. 

If it’s not your batteries then grey waste will be the culprit. Motorhome waste tank smells can be really unpleasant and grey waste that has been sitting for a long time in a sealed container (i.e. your tank) can smell strongly of rotten eggs and sulphur because it has stagnated in the tank. This is often a problem if you’ve been parked up wild camping for three or more days without being able to empty, and then move off with a full or partially full tank of grey waste water.


  • If your leisure batteries have boiled, the battery will have discharged sulphuric acid onto the battery and its container.  You must assume the battery and container are both coated so do not touch them.  Isolate the batteries in accordance with your motorhome instruction manual. Sadly, your battery has probably had it and will need to be replaced; most leisure batteries only last 3-4 years at most.  
  • If the smell is more general,  then you’ll need to flush through and clean out your grey waste tank and pipes  as described above.

How do I stop it happening again?

However you manage your leisure batteries, they do have a defined life and will not last forever, but there are steps you can take to prolongue their life.

The longevity of a motorhome or campervan leisure battery depends on frequency of discharge, depth of discharge and how soon it is recharged. A regulator or controller will ensure your battery runs through this charge and discharge cycle regularly.  You should not discharge your van battery any more than 50%. To do so can have a damaging effect on the battery and will certainly shorten its life.

Once your new battery is installed, keep an eye; further problems may indicate a problem with either the charging regulator if you have one, or your van’s electrical system.  If in doubt, get it checked by an expert.

We are not leisure battery experts and this is a complex field so we’re going to duck out at this stage and suggest you visit this really helpful website where you can find out everything you ever wanted to know about leisure batteries!

Start your beginners journey to life on the road with exclusive checklists, free downloads, tips & more

My motorhome smells damp & musty


A damp and musty smell in a camper can be a hard one to know the cause of and there are a number of possible scenarios.

Check for any obvious signs of condensation or mould, particularly where there is also a lack of circulating air; above a pull down bed or beneath sofa cushions for example.  Motorhome condensation and subsequent mould is caused by introducing moisture into the warm environment of your motorhome.  This could be from wet clothing if you’ve been out in the rain, the natural act of breathing over night combined with body heat or simply boiling fresh water in the kettle. This moisture becomes trapped in the air and eventually settles inside your motorhome as condensation, unless there is circulating air to move it around and take it away.   

Do you always have steamed up windows? Does your bedding feel very slightly damp at night? Do you have small patches of mould?  If so, you have ongoing condensation. 

Check under your bathroom and kitchen sink for leaking taps, it could be as simple as a loose jubilee clip or damaged seal allowing a trickle to leak from your fresh water tank.

A damp smell could also be caused by a leak externally,  where water is ingressing into the construction and fabric of the motorhome. It can take years for this to become noticeable, especially if it’s a small leak, which they usually are.


  • If condensation or mould are present, remove any wet clothing or laundry you have drying inside and open as many windows and roof lights as possible to ensure good cross-flow ventilation. Clean any mould with a specialist mould remover.
  • If you have a leaking tap then a competent DIY’er or plumber may well be able to fix it  Otherwise, a specialist motorhome workshop will be required.
  • If you have water ingressing and causing damp, no matter how little, it will damage the interior of your motorhome. This can be a major problem if identified and cost many £1000’s to repair. An expert will be able to use a moisture meter to check if this is the case.

How do I stop condensation?

There are lots of helpful things you can do to prevent condensation and some you can do to help manage the results of condensation. You can find out more about the causes of condensation and how to stop it in this post.

It smells fishy


It is highly likely that a fishy smell will be caused by a poor electrical connection that’s been overloaded and is cooking the surrounding PVC and plastic.  It could also be caused by cheap fuses overheating and melting the surrounding plastic.


  • Check the fuses, you may have a box or panel in a number of places so check your motorhome instructions.  If you have a melted fuse, remove any 230v power source from the mains, power down your electrical systems in the van, switch off the electrical master switch where your main fuse box is and then remove the offending fuse with plastic fuse removal or electrical pointy nose pliers.  If in any doubt about this, seek help from an auto-electrician or other suitably qualified person.
  • If the fuses all look ok, the you have a loose connection somewhere. This is where we advise you to find an auto-electrician as any diagnostics will involve removing socket covers and exposing wiring.  

It smells of ammonia


If this smell is isolated to your fridge then you have leaking coolant, which can be corrosive. You can also check for yellow powdery deposits along the piping at the back of the fridge, the presence of which will confirm a leak. Gas fridges are different to electrically powered fridges as they need a small amount of coolant to keep them working correctly.   

Otherwise, the smell may well be connected to your toilet as when urine is stale, it breaks down into ammonia.


  • If it’s your fridge that smells get a motorhome expert to look at your fridge as the leaking corrosive coolant can damage the fridge and further motorhome parts and fabric if not stopped.  It is likely that a new cooling unit will be required.
  • If you think it’s the toilet, then follow the advice above.

Unidentified Smells

There are a couple of smells which are really hard to describe and could be a number of things;

Decomposing pests can be an issue if you have your van in storage and have a double floor.  Mice love places like that to nest.  If you do find a body, check your wiring carefully as mice also love to chew through cables.

Air conditioning that needs re-gassing has a very specific vinegary/fishy/musty type smell.  If this is the case you will also notice that the unit is losing effectiveness.

Are you looking for more motorhome tips & practical advice? Check out these top posts…

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