What's that smell? When you smell bad eggs in the van ...

It is quite common to get a smell of bad eggs in the van. There are 4 possible reasons for this - 1 of them dangerous, but quite rare - your battery, 1 of them rare and expensive - your fridge, 1 of them highly unlikely - exhaust catalyzer ... and the remaining one is the most common - it's your grey water tank.

So the first thing to check is the dangerous one - on occasion an old or mistreated battery can start to cook and give off a smell of hydrogen sulphide - rotten eggs. This is quite a rare situation, especially with modern batteries, but you have to dismiss it first. The easiest way to check is to look for the obvious - the smell should be obviously coming from the battery. If this happens to you, I can't advise you as to the best course of action - it depends on the situation. Disconnecting the battery is the obvious thing to do, but only if you can do so safely. Calling for help is the most sensible thing to do.

Next is the fridge - if your fridge is very old and you know it's very rusty (round the back), then there is a possibility that it may finally have rusted through and leaked its chemicals. However this will be more of an amonia smell than rotten eggs. It is a very rare occurrence - usually the fridge stops working before it leaks, because it gets blocked inside with internal corrosion.

Next is an exhaust catalyzer - pre 95 classic Hymers (the subject of this blog and the FB group) don't have exhaust catalyzers, but I include this for any owners of later vans - it is pretty common knowledge that a worn exhaust cat can smell like rotten eggs. But if you have a pre 95 classic Hymer, it is very unlikely to be that.

So that brings us on to the commonest cause - the grey water tank. The grey water tank is the tank that catches all the water that goes down the plugholes from the sinks and shower. It may come as a surprise that it can occasionally stink so badly - far worse than what you see goes down the plughole, but there are good reasons for this.

The common reason is simply old age and a combination of other factors. Most grey tanks get emptied regularly, so they never actually get full. So what happens is that over the years, bits of food waste and other nasties that go down the plughole begin to accumulate by splashing on the walls of the tank, and also in the slime on the bottom of the tank. What happens is that you get a gradual build up over the years, and because the tank gets emptied so regularly, it never gets full enough to wash off the upper reaches.

Then what usually happens is that you get the first sunny day in spring, and up it comes through the plugholes. The smell can vary from an occasional whiff that makes you think that somebody has let go a cheeky fart, all the way up to a real pong in the van - it all depends on how bad it is.

The easiest way to check is to get your nose right down to the plugholes and hopefully you will get a confirmation whiff.

In any event, you should give your grey tank the once over every year anyway - especially if you full-time or use the van regularly.

There are several ways to solve the problem, including the famous "cola" method. As soon as anybody posts a question online about a smell, you will always get half a dozen people piping up saying to empty several litres of cheap cola down the sink and then go for a drive. It probably works, but I have never tried it myself. 

The reason I haven't tried it, is because it seems to be a temporary fix that doesn't get at the root cause of the problem. What the tank needs is the upper walls and ceiling getting washed, as this is where most of the smell should be coming from. The cola method may well do enough to dissolve away some of the smell, but there won't really be enough in there to effectively reach the upper bits of the tank. Whether cola will work in a three quarter full tank, I don't know ... I just prefer traditional household chemicals.

To do this the tank needs to be around 75% full, then add some chemical, and then go for a drive. If you are a regular van user you can even just build this into your regular routine - instead of emptying the grey tank automatically every time you have the opportunity - let it fill up, and throw a cup full of bleach down the plugholes, then drive for a day or so and then empty it the next pit stop. 

Other methods include using a cupful of blue toilet chemical, and I believe that Thetford even make a dedicated product.

Personally I use cheap supermarket bleach, or cheap pine smelling disinfectant, or a combination of the two.

All you have to do really is to ensure that you regularly drive with a half or three quarter full gray tank, so that the movement of the van sloshes the water up and over the side walls and roof.Quite often I will delay emptying the grey tank after we have both used the shower, to give it chance to slosh about in there.

The problem is particularly evident in the spring when the weather changes - your van may have been in winter storage, or you might just be setting off on holiday when it happens - if so, you hardly have to think about the other possible causes - it is always the grey tank.

Another tip is this - if you want to get some water into your grey tank for cleaning purposes, and don't fancy running the water pump for ages and ages, then I have found that if you have the standard old Hymer waste outlet - the one with the round wheel valve, then you can usually stuff the end of a hosepipe up it and shoot water into your grey tank that way - give it a try - but don't overdo it and keep an eye out inside the van - if you fill up the tank right to the top by doing this, it can come out of the plugholes inside.

Another tip for full timers is as I mentioned above, if you get in the habit of a small quantity of bleach every week or so, you will minimise the chance of ever getting the smell ever again.

Yet another tip is to get up close and personal with your grey waste. Give it a smell when you empty it - you can usually get a bit of advance warning if you have a slowly growing problem inside the tank and you will generally detect it this way long before it gets bad enough to come up through the plugholes.

Don't taste it though!