In one of our bathrooms there were times when there was quite a bad smell; it came up from the pipes and the siphon canister. We tried everything: bleach, cleaning products, of course cleaning the siphon canister regularly… and nothing.
The fact is that as we told you in this other article, we made LAB because one of the multiple uses it could have was precisely to remove bad odors in the bathroom. The way LAB works to achieve this is as follows.
Lactic Acid Bacteria have the property of reproducing at a great speed, more than most other beings in their environment. However, they are not harmful to these, which makes it very useful for the garden and compost as it is not a biocide.
What happens if LAB is applied to the siphon canister?
What will happen is that, since the bad odor comes from bacteria and fungi that decompose organic remains, when LAB is applied, the Lactic Acid Bacteria will begin to reproduce so fast that they will literally take the space away from the ones that produce the bad odor.
We have tested it not by pouring LAB in water, but in the siphon bottle directly. To do this, you just have to locate the siphon bottle, which will be a metal lid on the bathroom floor, and unscrew it.
You will see a circular pipe, with a circular structure surrounding it, where the water is stored. This is where you should pour the LAB. Close the lid and you will see how in a short time the bad smells will disappear.
This trick has been applied by other friends and family members and has also worked wonders for them.
Step by Step: Applying LAB to the Drain
- Locate the siphon canister: a round or square metal lid set into the bathroom floor, usually in a corner or near the shower.
- Unscrew or pry off the lid. Have a cloth ready — the trapped water can splash.
- If the canister is very dirty, scoop out hair and sludge first; LAB works better when it’s not fighting a solid blockage.
- Pour 100–200 ml of undiluted LAB directly into the water reservoir around the pipe.
- Replace the lid and avoid running large amounts of water down that drain for a few hours so the bacteria can settle in and start colonizing.
Why It Works Where Bleach Failed
Bleach and chemical drain cleaners kill everything — including the odor-producing bacteria — but only for a few hours. The biofilm inside the pipe survives, and within days the smelly microorganisms repopulate the siphon. LAB takes the opposite approach: instead of sterilizing, it outcompetes. Lactic acid bacteria multiply faster than the microbes that generate sulphurous and putrid smells, and the mildly acidic environment they create makes it hard for the odor producers to return. The effect lasts for weeks rather than hours.
Other Places Where LAB Removes Odors
- Kitchen sink drain: Grease and food scraps make it a classic odor source; pour LAB down the plughole at night.
- Compost bin: A light spray over fresh scraps reduces the smell of decomposition and speeds up the process.
- Pet areas: Diluted LAB (1:20 in water) sprayed on floors neutralizes urine smells.
- Washing machine: A glass of LAB in an empty warm cycle helps with musty odors in the drum and pipes.
How Often Should You Reapply?
In our experience one application keeps the bathroom odor-free for one to three months, depending on how much the drain is used. When the smell begins to return, repeat the treatment — there’s no risk of overuse. For prevention, a small dose once a month keeps the bacterial community stable. Keep in mind that homes that use bleach or strong chemical cleaners frequently will need to reapply more often, since those products wipe out the LAB colony along with everything else. If the odor persists after two applications, the cause is probably mechanical: a dried-out trap, a broken seal, or a venting problem that needs a plumber rather than more biology.
Frequently Asked Questions
Is LAB safe for pipes and septic tanks? Yes — it’s a living culture, not a corrosive product. It can’t damage PVC or metal, and it actually benefits septic systems by adding useful microbes.
Can I use store-bought LAB instead of homemade? Yes. Commercial lactobacillus concentrates for gardening work the same way; follow the dilution on the label or use them neat for drains.
Does it remove the smell instantly? Improvement is usually noticeable within 24–48 hours as the LAB population takes over the siphon. It’s not an instant air freshener — it’s a lasting fix.
What if the smell comes from humidity, not the drain? Check the siphon first — it’s the most common source — but if walls or towels smell musty, ventilate daily and spray diluted LAB on grout and silicone joints where mold starts.
We hope you liked it, if you have any questions you can write us here and we will answer you as soon as possible.
