How to Clean and Sanitize a Fermenter: Stainless, Conical and Plastic

The short answer: clean first, then sanitize. Cleaning removes the soil you can see (krausen, trub, beer stone) with a hot alkaline brewery cleaner. Sanitizing then kills what's left, just before the fermenter is filled. Sanitizer can't work through dirt, so a quick sanitizer rinse on a dirty tank does very little. Take apart every valve and fitting that touches beer, every batch.

Cleaning vs sanitizing

	Cleaning	Sanitizing
What it removes	Soil: krausen, yeast, trub, hop residue, beer stone	Microbes left on a clean surface
When	Right after emptying the fermenter	Just before it's filled or closed up
What with	Hot alkaline brewery cleaner (PBW-type); an acid cleaner now and then	No-rinse acid sanitizer (Star San-type), iodophor or peracetic acid
Rinse after?	Yes, rinse well	No, for no-rinse sanitizers

How to clean a stainless or conical fermenter

1. Rinse right away. Hose out the yeast and trub while it's still wet. Dried krausen takes far longer to remove.
2. Take it apart. Remove the butterfly and sample valves, the thermowell, the PRV and every tri-clamp fitting. Pull the gaskets and check them for cracks, flattening or stains; replace any that look tired. Most infections start in valves and gasket grooves, not on the open walls.
3. Clean hot. Fill or recirculate with an alkaline brewery cleaner mixed to the label rate in warm water, around 120 to 140°F (50 to 60°C). Soak the small parts in a bucket of the same solution.
4. Use a spray device for conicals. A rotating CIP spray device on the top port, fed by a pump, sprays cleaner over the whole inside of the tank, including the underside of the lid. Run it for 20 to 30 minutes.
5. Scrub only with soft tools. Use a soft cloth or non-scratch pad on stainless. Never steel wool: scratches hold bacteria and can rust.
6. Rinse thoroughly with clean water until there's no slippery feel.
7. Acid-rinse every few batches. An acid brewery cleaner removes beer stone and mineral film and keeps stainless passive. Rinse afterwards.
8. Reassemble and store dry, or sanitize and seal the tank if you'll fill it soon.

How to sanitize a fermenter

1. Mix a no-rinse sanitizer to the label rate. Star San-type acid sanitizers are typically 1 oz per 5 gallons of water.
2. Wet every surface the beer will touch: spray or swirl the tank walls and lid, and run sanitizer through the valves.
3. Keep it wet for the contact time on the label, usually 1 to 2 minutes.
4. Drain and fill. Don't rinse no-rinse sanitizers. The foam is harmless and gives the yeast no trouble.

Sanitize anything that touches cold wort or beer: hoses, the thermowell, the sample valve, transfer fittings and your hands or gloves. A spray bottle of sanitizer is the easiest way to hit fittings and tri-clamp faces during a transfer.

Which sanitizer should you use?

Sanitizer	Rinse?	Good for	Watch out for
Acid no-rinse (Star San-type)	No	Everything: stainless, plastic, glass	Loses strength in hard water or when the mix goes cloudy; mix fresh
Iodophor	No, at 12.5 ppm	Stainless, glass	Can stain plastic and silicone
Peracetic acid	No	Commercial CIP, stainless	Strong fumes; handle concentrate with care
70% alcohol spray	No	Small parts, tri-clamp faces, sample ports	Flammable; not for whole tanks
Chlorine bleach	Yes, very well	Plastic buckets, occasionally	Pits stainless steel; leftover chlorine makes medicinal off-flavours. Avoid on stainless

Plastic fermenters

Plastic buckets and carboys clean the same way, with two differences: soak instead of scrubbing, because scratches hide bacteria, and replace them once they're scratched or smell of old beer. Stainless tanks last for decades with the same routine, which is one reason many brewers move to a stainless Unitank.

Common sanitation mistakes

Mistake	What happens	Fix
Sanitizing without cleaning	Bacteria survive under soil and biofilm	Always clean first
Not taking valves apart	Beer and yeast dry inside the valve and seed the next batch	Strip and soak valves and gaskets every batch
Old, flattened gaskets	Leaks and crevices that can't be cleaned	Replace tri-clamp gaskets when they crack, flatten or stain
Steel wool or harsh scrubbing	Scratches that hold bacteria	Soft cloths and hot cleaner do the work
Bleach on stainless	Pitting and chlorophenol off-flavours	Use a no-rinse acid sanitizer instead
Forgetting the cold side	Infection from hoses, sample ports or the thermowell	Sanitize everything that touches wort after the boil

Frequently asked questions

What's the difference between cleaning and sanitizing?

Cleaning removes visible soil. Sanitizing reduces the microbes left on a clean surface to a safe level. You need both, in that order.

Do I have to rinse Star San?

No. Used at the label rate it's a no-rinse sanitizer, and the foam won't hurt the yeast or the beer.

How long does sanitizer need to stay on?

Usually 1 to 2 minutes of wet contact for acid no-rinse sanitizers. Check the label for yours.

Can I use bleach to clean a stainless fermenter?

Avoid it. Chlorine pits stainless steel and can leave medicinal off-flavours. Use an alkaline brewery cleaner, then a no-rinse sanitizer.

How often should I replace tri-clamp gaskets?

Whenever they crack, flatten, stain or hold a smell. Silicone gaskets are cheap compared with a lost batch.

How do I clean a conical fermenter without climbing into it?

With a clean-in-place spray device on the top port and a pump recirculating hot cleaner, then the same for sanitizer. Take the valves off and clean them separately.