Recently the biogas started to smell a bit, it had the particular odour of sewage when the burner was lit. This is not what you want to smell when you put the kettle on for your morning coffee. The smell means it is time to change the gas filter, luckily I had ordered a kit months ago. The gas filter is a plastic pot filled with activated charcoal, the pot has holes in the top and the sides so gas can travel through it. A rubber seal around the pot makes sure the gas has no option but to travel through the charcoal filter. They are fairly easy to change, having been designed that way, but there are some important things to note when doing this routine maintenance.

All you really need to do when changing the gas filter is;

1. remove the stickers from the new filter canister.
2. lever the lid of the gas collection pipe up until you can open it.
3. pull out the old gas filter using the handy rope handle.
4. place the new filter in the gas collection pipe.
5. replace the lid of the gas collection pipe.
6. open the old filter and add the charcoal to the compost pile or the worm farm.

However… I made several mistakes that led to us having no gas for several days and smelled fairly bad too.

My first mistake was not looking to see which way up the rubber seal on the gas collection pipe lid went. In fact I mistakenly threw the seal out as I thought it was from the old canister at first. This seal stops the filtered gas from escaping into the atmosphere, so it’s pretty important. The seal is contoured, so it needs to face the right way.

My second mistake was to try changing the filter when the balloon was full of gas. Nobody wanted to use the burner because of the smell, so the balloon was very full of lovely methane (and sulphur compounds). I levered off the gas collection pipe lid and got a face full of smelly gas as the balloon deflated entirely.

Other than those two mistakes, the whole process is fairly easy and no fuss. Next time I will change the filter as soon as I get a tiny whiff of smell and make sure to use all the gas before I change it. I wish I had taken photos of which way the seal goes in the lid, but I didn’t. Instead I took a screen shot from the assembly app to remind myself which way the rubber seal goes.

This system is so easy to assemble and maintain that I wonder why everyone doesn’t have one. It needs a little bit of maintaining now and then, but what system doesn’t? The benefits far outweigh the inconvenience.

The toilet is going to need a new water pump seal soon and the chlorine filter for the effluent needs replacing too, I am hoping those go as easily (but with less mistakes) as the gas filter change.