How to clean a homebrew fermenter, and why not with soap

You've just bottled a batch, the fermenter's sitting there with a ring of dried yeast around the inside, and you reach for the dish soap, because that's what you reach for with everything else in the house. Put it down. Soap is the one thing that doesn't belong anywhere near a fermenter, and the reason isn't squeamishness about chemicals, it's that dish soap is built to leave a film behind and that film is what ruins your next brew.

What soap actually does to a beer

Dish soap works by clinging. It has to cling, otherwise it'd sheet straight off the plate along with the grease and never get anything clean, and that same clinginess is why a fermenter you've washed in it is still carrying soap long after the water runs clear. The film sits there on the wall, and when you pitch your yeast into it a fair share of those cells hit the surface and die, so you end up with a sluggish ferment, or one that stalls halfway and never finishes.

Then there's the smell. Every dish soap on the shelf is perfumed with something, lemon usually, and that perfume moves out of the plastic and into the beer over the 2 weeks it's sitting in there. It doesn't taste like lemon by the time it reaches the glass. It tastes like soap, and it's the kind of fault you can't fix afterwards, you can only tip it out.

The scratches are the other half of it

Soap gets people scrubbing, and scrubbing a plastic fermenter with anything abrasive puts fine scratches in the wall. You can't see them and you certainly can't rinse them out, and they're deep enough to hold wild yeast and bacteria that your sanitiser won't reach properly. That's usually where a sour or cidery note comes from in a brew that was otherwise made carefully, and it's why a fermenter that's been scoured for 3 years running gives you more trouble than one that just gets soaked.

So the rule with a fermenter is soak it, don't scrub it. A soft cloth or a proper bottle brush for anything that hasn't lifted, and never a scourer or steel wool.

Cleaning and sanitising are two different jobs

This is the bit that trips people up, because the two words get used as though they mean the same thing and they don't. Cleaning takes the visible material off, which is the yeast cake and the dried krausen ring around the waterline. Sanitising kills what you can't see. A sanitiser poured into a dirty fermenter does very little, because the organic muck shields the bugs sitting underneath it, so the order matters and it's always clean first, sanitise second.

What to actually do

1. Rinse it with warm water the moment it's empty. Yeast and hop residue come off in seconds while they're still wet, and set like concrete once they've dried on.
2. Clean it with a brewing cleaner rather than a kitchen one, and give it time to soak instead of going at it with your arm.
3. Do the tap and the lid seal separately. The tap comes apart, and the gunk that hides inside the barrel of a tap is easy to miss, because the fermenter looks spotless from the inside.
4. Sanitise with a no rinse sanitiser and then leave it wet. You don't rinse a no rinse sanitiser, which sounds obvious written down and is still worth saying out loud.
5. Let it air dry upside down with the lid off. A tea towel puts back everything you've just taken off.

If you're not sure which bottle does which job

Ask us. Plenty of people who've been brewing for years still have cleaning and sanitising the wrong way round, so it's a good question rather than a beginner's one, and it takes about 20 seconds to answer over the counter.

Shop related products

• S-04 Safale Ale Yeast 11.5g. The English ale yeast, and the one soap residue knocks over fastest.
• US-05 Safale Ale Yeast 11.5g. A clean American ale yeast for pale ales and IPAs.
• S23 Saflager Lager Yeast 11.5g. The lager yeast, for a cold ferment.
• Coopers Original Draught 1.7kg. A straightforward kit to put in the fermenter once it's clean.

Did you know we stock the cleaning gear itself in the shop. Brewclean colloidal cleaner and the 1 litre refill, Beer Essentials no rinse sanitiser, Brew Sanitize, bottle brushes including a stubby one for PET bottles, and the 30 litre and 60 litre fermenter complete systems. None of that's on the website, so give us a ring on (08) 8536 4333 to check what's on the shelf.

The whole homebrew range lives in our homebrew collection, and if you'd rather work out what you need by answering a few questions, Brewhilder will walk you through it.

More on this

• Why every homebrewer needs a decent fermenter
• What makes homebrew beer taste off, and how to stop it
• What fermentation actually does, and how to keep yeast happy

My rule about the dish soap is that it doesn't get past the kitchen sink, which is a lot easier to remember than anything I could tell you about residue.

Cheers,
Candeece