Bong: what it is, how it works and what the water really filters
By the Golden High teamUpdated 25 October 20268 min read
Accessories
A bong (called a « bang » in France) is a water pipe: the smoke from combustion bubbles through water before you inhale it, which cools it down and makes it feel smoother on the throat. But water is a poor filter: a study by MAPS and California NORML measured around 30% more tar per unit of cannabinoids than an unfiltered joint. Here is how a bong works, what it really changes, its risks and how to keep it clean.
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The bong, a water pipe.
According to the French Monitoring Centre for Drugs and Drug Addiction (OFDT), the word bang (or bhang, bong) usually refers to a water pipe used to smoke cannabis, either home-made or bought in a shop. The term comes from a Thai word for a bamboo tube. In France people tend to say « bang »; elsewhere, « bong » has become the standard word.
The principle is as old as water pipes themselves: draw the smoke through a liquid before inhaling it. What has changed are the materials (glass, silicone, acrylic) and the add-ons, such as percolators, which multiply the bubbles.
- What the water does: it cools the smoke and makes it less harsh on the throat.
- What it doesn't do: it doesn't make the smoke « healthy ». Most of the tar and carbon monoxide gets through.
- What that changes: cooler smoke gets inhaled deeper and in bigger volumes.
- The rules in France: selling water pipes is legal in France, as long as there is no incitement to use controlled drugs.
How it works
How a bong works, piece by piece.
Every bong relies on the same mechanics: the suction you create pulls the smoke from the bowl into the water, then up the tube. To understand « how to use a bong », you first need to know its parts.
When you inhale through the mouthpiece, air is drawn through the bowl: the material burns, the smoke travels down the stem, bubbles through the water, rises and fills the tube. Opening the carb or pulling the bowl lets fresh air in, which pushes all the built-up smoke out at once. That concentrated « hit » is what the bong is known for, and also its main risk: a huge puff inhaled in one go.
A bong is not a harmless thing to pass around: the mouthpiece goes from mouth to mouth and stagnant water quickly breeds micro-organisms. Changing the water every session and keeping your own mouthpiece are basic hygiene habits.
The families
Glass, silicone, percolator, gravity: the different bongs.
| Type | Principle | Pros | Cons |
|---|---|---|---|
| Glass | The reference model | Neutral taste, easy to clean, you can see the build-up | Fragile, heavy |
| Silicone | Flexible body, often takes apart | Unbreakable, travels well | Can hold on to smells |
| Acrylic | Rigid plastic | Very cheap | Scratches, ages badly, less neutral taste |
| Ceramic, bamboo | Traditional materials | Good-looking | Opaque: hard to tell if it's clean |
| Percolator | One or more chambers that split the smoke into fine bubbles | Cooler, smoother smoke | Harder to clean, heavier draw |
| Gravity bong | A bottle that rises or sinks in water to pull in the smoke | — | Often home-made from plastic: the riskiest |
The percolator is the part that sets high-end bongs apart: a glass diffuser (tree, honeycomb, dome) that breaks the smoke up into lots of tiny bubbles. More contact with the water, so cooler smoke. Not cleaner smoke though, as you'll see below.
Gravity bongs and home-made bongs: Drogues Info Service (the French public drug helpline) is very clear. Bongs rigged up from plastic bottles or cans give off highly toxic acidic fumes when heated, which can lead to serious complications: black sputum, pulmonary haemorrhage. Its advice: don't use home-made bongs.
What the studies say
Water doesn't filter everything, far from it.
The idea that « water filters the smoke » is the most widespread belief about bongs. It's partly true for temperature, much less so for toxicity. Here's what the available research shows.
MAPS & California NORML
Dale Gieringer's study compares joints, water pipes and vaporisers. The unexpected result: the bong delivered around 30% more tar per unit of cannabinoids than an unfiltered joint. The water also traps some of the cannabinoids, which are sticky, so people smoke more to get the same effect. Limitation: the herb tested contained only 2.3% THC.
JAMA Network Open · 2022
Berkeley researchers measured fine particles (PM2.5) during 8 bong sessions in a 20 m² living room. Average: 1,300 µg/m³, roughly four times the levels measured for cigarettes or hookah in earlier studies. 90 minutes later, levels were still at half the peak; in one session tracked for 12 hours, they were still more than ten times the background level.
Revue de pneumologie clinique · 2016
Lung specialists in Brest describe the bong as a common and dangerous way of using cannabis: intense, rapid effects and specific complications, including coughing up blood, possibly linked to the volume of smoke inhaled and to burning plastic parts.
Drogues Info Service
Coughing, chronic bronchitis, damage to the airways: these risks of smoked cannabis increase with tobacco and with the use of bongs or hookahs.
In other words: the bong softens the feeling, not the smoke. And the way it works pushes you to inhale bigger volumes, more deeply. Full references at the bottom of the page.
The verdict
What a bong gives you, and what it costs.
- Cooler smoke, less irritating on the throat in the moment.
- No paper, no tobacco: only the material itself burns.
- Often a cleaner taste with a clean glass bong.
- More tar per effect than an unfiltered joint, according to the MAPS-NORML study.
- Big hits in one go, so a harder-hitting effect that's tougher to dose.
- Lots of fine particles in the room, which also affect anyone around.
- A bulky object, fragile, that gets dirty fast and isn't great for sharing.
If what you mainly want is less harsh smoke, a bong isn't the only answer. We compared the different ways of consuming in how to consume flowers and resins, and the ins and outs of vaping in vaping cannabinoids: what you need to know.
Maintenance
Cleaning a bong without the hassle.
A dirty bong isn't just unpleasant: stale water and tarry residue give an acrid taste and keep deposits building up. Here's the simplest routine for a glass bong.
Change the water
Every session, no exceptions. Empty it, rinse with clean water, let it drain.
Take it apart
Remove the bowl and the downstem: these are the parts that get dirty fastest.
Alcohol and coarse salt
Pour isopropyl alcohol and a handful of coarse salt into the base, cover the openings and shake: the salt works as a gentle abrasive.
Rinse and dry
Rinse thoroughly with hot water until the smell of alcohol is gone, then let it air-dry.
For a silicone bong, hot soapy water is often enough. Avoid alcohol on acrylic, as it can damage it.
Don't want a bong?
Alternatives to the bong.
No bong? You don't need one to enjoy a flower. The most important part happens before: well-ground material burns more evenly. A 4-piece metal grinder already makes a real difference, and we explain how to pick one in our grinder guide.
For rolling, a thin, neutral paper like OCB Premium rolling papers lets the taste of the flower come through without masking it. And to build your kit, have a look at our accessories collection and our pick of 5 accessories that really change your experience.
Harm reduction: whatever the method, start with small amounts, don't consume if you feel tired or anxious, never drive afterwards and avoid smoking in a room where other people are present, especially children. Adults only.
Your questions
What people ask us about bongs.
What is a bong?
A bong is a water pipe: the smoke bubbles through water before being inhaled, which cools it down. The word comes from a Thai term for a bamboo tube. In France it's often called a « bang ».
What's the difference between a bong and a bang?
None: it's the same object. « Bang » is the everyday word in France, « bong » the international one.
Does bong water filter the smoke?
It cools it, but filters poorly. A study by MAPS and California NORML measured around 30% more tar per unit of cannabinoids than an unfiltered joint, because the water also traps some of the cannabinoids.
How does a bong work?
Inhaling through the mouthpiece draws air through the bowl: the smoke goes down the downstem, through the water, fills the tube, then gets cleared in one go when you open the carb or pull the bowl.
What is a gravity bong?
A device where a bottle rises or sinks in water to pull in the smoke. It's often home-made from plastic, which Drogues Info Service strongly advises against: when heated, plastic gives off highly toxic fumes.
Is a bong less harmful than a joint?
Not according to the available data: more tar per effect, big hits inhaled deeply and lots of fine particles in the room. The feeling is smoother, the smoke isn't.
Is it legal to buy a bong in France?
Yes: in France, selling water pipes is legal as long as there is no incitement to use controlled drugs. What matters legally is what you put in it. Rules differ from country to country.
How often should you clean a bong?
Change the water every session. A full clean with isopropyl alcohol and coarse salt is due as soon as the glass looks cloudy or the taste turns acrid.
Sources
The references cited in this article.
- OFDT. Glossary: Bang (in French).
- Gieringer D., MAPS / California NORML. Marijuana Water Pipe and Vaporizer Study.
- Nguyen P.K., Hammond S.K., JAMA Network Open (2022). Fine Particulate Matter Exposure From Secondhand Cannabis Bong Smoking.
- Paleiron N. et al., Revue de pneumologie clinique (2016). The cannabis « bang »: an original, common and dangerous way of consuming (in French).
- Drogues Info Service. Drug dictionary: Cannabis (in French).
- Drogues Info Service. Your questions, our answers: Water pipe (in French).
