Monday 5 September 2016

On smelly grey tanks ...

Quite often it's not the toilet tank that smells - it's the wastewater tank ...

Over the years I noticed that the smell came usually from an empty tank. I think that's because gunge gets coated on the inside of the tank, has plenty of air to react with in the heat, so produces more smelly gas, that then percolates up through the plug holes. Blocking the plugholes does help - especially when you are driving and don't want to stop.

More recently I have been experimenting with letting the tank fill up with grey water, but making sure that the "mix" is reasonable - ie not too dirty and a fair amount of soap in the water. The rationale behind this is that a fair amount of soapy water sloshing around the inside of the tank actually keeps the inside walls cleaner. I have a feeling, but can't prove, that as I said above, it's a generally dirty empty old tank that causes the smell, not the actual grey water itself. The trade off of course is that you are burning diesel by carrying round waste water, but this is less of an issue if you are long term on a site. I have had less smell with this method, although I haven't been abroad this summer into really hot climates. And when I empty a nearly full grey tank - it generally doesn't smell any worse.

I have never tried the coca cola method, and I think to a certain extent it's a bit of an urban myth. If you pour 4 or even 6 bottles into the tank, or any other chemical on its own, it will only ever cover the floor of the tank with half an inch or so, which will clean the floor and half the walls if you slosh it about by driving, but it will never clean the whole of the tank. I think the only way to be sure of cleaning the whole tank is to fill it almost to capacity, introduce a copious quantity of any type of detergent (they are all basically a variation on soda) and then go on a long drive followed by a full discharge. This of course is roughly the same as letting the tank fill up with normal grey water which already contains a certain amount of detergent, but rather than emptying it prior to driving, driving with it, so it sloshes around, and only emptying it when full or nearly full. That's what I have been doing recently, and my impression is that there is less smell. Having the tank quite full, quite often, will also have the effect of keeping the level sensors clean, especially the two upper ones, which, if you are in the habit of emptying the tank regularly, or dribbling, will never get much contact with the water, so will tend to get worn or coated and eventually malfunction. I am tending to think that never letting the tank get full occasionally is part of the problem.


A friend of mine in the trade recommends the following method - but this only works if you are on a trip, with regular driving. Pour a good quantity, at least a full small bottle or half a big bottle, of blue toilet chemical down the sink, together with a full boiler full of hot water. By this I mean switch on the Truma boiler to it's highest setting, and wait 30 mins, then let the whole lot go down the sink, into the tank, until it runs cold. Then carry on with your trip, letting your waste water fill the tank as you go. After a few days, empty the tank at a disposal point. This should have the dual result of getting rid of the smell, and cleaning the tank.

1 comment:

  1. I've only been either caravanning or motorhoming since I bought my first camper some forty eight years ago. I was told about various ways to try and keep the waste tanks clean and odour free, shower sink and also toilet. It wasn't until I did a fairly substantial tour of the United States, east to west and north to south, that I was told about the cola method. Until this time I'd tried every other way under the sun to a greater or lesser success rate. Anyroadup, for me and the camper, the cola method works wonders. Should rename it MR SHIFTSHIT. Sometimes when I feel flush I get a bottle of the cheapest nastiest perfume from the cheapest nastiest markets and pour that down the plughole, sweet smelling for days and days.

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