How do percolators work?


Why use percolators?

Most people have seen them on bongs and bubblers, but many still don’t fully understand them. Simply put, a percolator forces smoke to travel through water in order to filter it. This filtration cools the smoke and makes hits much less harsh. They come in many different designs, but all ultimately accomplish the same thing. If you prefer smoother hits, or you’re looking for a healthier way to smoke, percolators are definitely something worth having in a smoking piece.

There are three ways that percolators help you:

  • Cooling – The smoke is extremely hot as it comes from the bowl, some lighters can get as hot as 3600 F / 2000 C. The water slows down the smoke’s path to your lungs, giving the smoke significantly more time to cool down. Additionally, forcing the smoke to interact with water gives it a chance to dissipate its heat into the water, which dissipates heat from the smoke better than air.
  • Moisturizing – Another reason taking direct hits from a joint or pipe with no water filtration is so incredibly harsh is that the hits are dry. Forcing the smoke to interact with water causes some of the heated water to turn into water vapor, thereby moisturizing the hit, making the smoke less harsh on your lungs.
  • Filtration – Filtration of the smoke occurs when the smoke makes contact with the water, therefore the more surface area of bubbles you have, the more filtration you have. Water, or H2O, is a very polar molecule. This means that when the smoke interacts with the water, the water magnetically attracts polar contaminants, taking them out of the smoke. Water Filtration isn’t great at getting small contaminants or non-polar contaminants, but the filtration in addition to cooling and moisturizing makes for much smoother hits and happier lungs.


BUT: Does it filter out THC?

This is a common misconception about percolators and water filtration. Joint and pipe enthusiasts often complain that the water filters out the THC, which is why they prefer to not use additional percolators or any water filtration at all. However, if you’ll note my little chemistry lesson above, you’ll know that water is only good at attracting polar compounds from the smoke. Fortunately, THC, as well as many other cannabinoids, are non-polar substances, so the water would do a poor job at taking the THC out of the smoke. Anyone who’s made cannabutter with water has thrown out that water. You can throw the water away for the same exact reason. On the other hand, THC dissolves well in fats and oils because fats and oils are non-polar. This is why you can be confident that water filtration and percolators don’t decrease the THC content of your smoke.

There has only ever been one study done on the matter. It suggested that water was indeed able to filter a minute amount of THC from the smoke, however the methodology has been disputed, and the study has never been repeated. Additionally, for the chemistry-related reasons stated above, conventional wisdom would say that THC isn’t filtered out of the smoke. Until a study definitively proves it one way or the other, we can’t be certain, but our analysis is that percolation does NOT filter out the THC. Ultimately you should weigh the evidence and make your own informed decision.


Can you have too much percolation?

This is another common myth. While it is true that the additional cooling and moisturizing you get after the first one or two percolators is diminished, when it comes to filtration, you just can’t have enough percolation. Filtration occurs when the smoke makes contact with the water, so in order to get 100% water filtration, you need the surface area of the bubbles to be equal or greater than the surface area of the smoke. However the surface area of the smoke is many orders of magnitude greater than the surface area of the bubbles even with extremely effective and numerous percolators.


Percolator Types



Downstems are definitely the most commonly overlooked percolators. Before other percolators entered the market, downstems were the only percolators, and they are what set water pipes aside from dry pipes. Certain pipes are considered ‘stemless’ when they don’t have a downstem that comes apart from the water pipe as a separate piece, but even stemless bongs sometimes use stem percolators. The design is very simple, there’s a tube that reaches into the water and the air has to travel through it and comes out as bubbles. Adding holes, slits, or sometimes more complex mini-percs, on the end of a stem can increase the number of bubbles and therefore their surface area, thereby increasing its percolation power. The biggest advantage to downstems as percolators is their size / mobility. Since downstems are easily removed from a bong, they can be easily cleaned or replaced as necessary. If you prefer to like to use a simple, no percolator bong, we recommend spicing it up by adding an improved downstem, and you still keep all the benefits of your simple perc-less bong while retaining the additional percolation power.


Tree Percs


Tree Percolators are among the first percolators separate from downstems used in water pipes, and there’s a lot to say about them. If you understand its design, you understand perfectly how percolators work. There’s a tube that goes up through the middle, that tube attaches to a bunch of arms up high, and those arms descend from that attachment point into the water. This way air comes from below and is forced up through the central tube and down the arms of the perc where it enters the water as bubbles. The arms are typically diffused with at least 2-3 slits in each arm.

Although they are the most common, and probably exactly what most people think of when they think of a percolator, there are a lot of problems with their design compared to other percs. The most glaring disadvantage is breakability. Anyone who has been around bongs for awhile has seen a tree perc break. For every arm, there is a joint attaching it to that main tube mentioned above. These connections are melted together, and usually are no more than 2-3mm thick at most. Even if they are 4mm+ thick, there’s always going to be a weakest link. Furthermore, smoke always takes the path of least resistance. The tree percolator’s design means that the top slits of each arm are closer to the water’s surface and therefore experience the least resistance. This means that even though your tree percolator may have 10 slits down the side, only the top two or three actually have smoke go through them. Additionally, if your bong is tilted at all to one side, like many people do when they take a hit, one side will be closer to the surface than the other side, rendering half of the perc less effective. This can be a problem with almost all percolators to a degree, but it’s more pronounced with tree percolators. Additionally, it’s very uncommon for the slits of a tree perc to be perfectly level, so the higher slits experience less resistance thereby rendering the lower slits less effective.

There are still some reasons to have a tree perc. One important reason is visual interest, which is important to a lot of smokers. All those glass rods do look good while working in harmony. Additionally, some people like them for the nostalgic value. There was a long period of time when tree percs made up more the majority of all percolators, so some people just like them because their first bongs had tree percolators. Regardless of artistic or nostalgic value, tree percs do in fact still do their job, and do it without creating much drag, so while a tree perc isn’t inherently bad, it’s just not our favorite.


Showerhead Percs


Showerhead percolators go by many other names, such as UFO, tire, and others. They were one of the first percolators to come after tree percs and have a very similar design. They use a tube that comes up through the middle from the chamber below, which is covered by a larger tube reaching down to the perc where air and smoke exits into the water as bubbles. This design can be clearly seen in the image on the left. There are many different designs, ranging from 4 slits to multiple tiers of 50-slit showerheads, as well as more artsy designs with bulging spheres in the middle to resemble flying saucer type UFOs, hence the name. They suffer similar downsides to tree percs, however since the slits are not stacked vertically, their water flow tends to be more evenly distributed. Furthermore, since they have less individual parts, they’re less prone to breaking. Showerhead percs may not be the best available, but they make an excellent improvement to downstems. It’s typical for stemless pieces to start off with a small showerhead as the first perc before the next larger perc. Although multiple showerhead percs are often stacked inside a single chamber, this makes the lower showerheads less effective because the airflow is distributed more heavily to the top showerheads.


Honeycomb Percs


Honeycomb percolators are our favorite percs here at Stoner Pros. As disc percolators, they are small, easy to make, and take up very little vertical space. This means they’re cheap and you can fit a lot of them into a small vertical space. Additionally, they are one solid piece with no weak spots, which is why we recommend honeycomb percs with thicker (7mm+) pieces, as having a 2mm Tree Perc inside a 9mm tube completely defeats the purpose of 9mm glass. Honeycomb percs also pack a lot of punch in terms of percolator power. They can compete with, and beat, almost all other percolators in this arena. Finally, the numerous holes don’t create much drag, so you can consistently get a perfect hit without being slowed down. Depending on the size of the holes of the perc, water may sit on top, or always fall through just to pull water up through the perc when you hit the piece. As long as water flows through it, it doesn’t matter if water is sitting on top of it or not.


Inline Percs


Inline percolators are simple slitted tube percs, similar to downstems. However, unlike downstems they tend to sit flat in the water, whereas downstems typically enter the water at an angle, so they don’t have the problem of some slits being higher than others. This means the only limit to the number of slits is the length of the tube, which is why it’s fairly common for tubes using large inline percolators to be expanded horizontally, like the piece in the image on the left, to accomodate longer inline percs. Although this makes them more effective, the longer the perc, the easier it is to break. Much like showerhead percs, they are often used in stemless pieces as the first minor percolator which then leads to the first main percolator above it.


Matrix Percs


Matrix percolators, sometimes called Birdcage, have become a lot more common lately. I normally wouldn’t give them their own category since they’re essentially the same as stacked showerhead percolators, but their prevalence has earned them their own category. They basically function the exact same way as a stack of showerhead percs. Much like stacked showerheads, the top rows have less resistance and therefore make the lower holes less likely to pull any smoke through. This means that a one-row showerhead with more evenly distributed slits can be more effective than a matrix percolator with far more rows and holes. Even though they don’t provide any significant functional advantage, their aesthetic makes them desirable, as they appear to provide more percolation than they really do, although they still do an adequate job regardless.


Turbine Percs


Turbine Percolators are another great disc percolator. Similar to honeycombs, their low height makes them easily stackable, and the fact that they are one solid piece makes them incredibly durable, not to mention easy to produce. The percolation power is similar to honeycomb percolators, however with larger and fewer holes, they provide a bit less percolation power. The trade off is two-fold. First, if you pull through them at the right speed you get beautiful cyclone effect, as seen on the left. The cyclone effect throws the water up along the edges of the piece rather than up through the middle, making turbine percolators function as effective splash guards, especially if the walls above the perc hit a ceiling where the tube turns into a smaller tube for inhaling the smoke. Sometimes turbine percolators are used exclusively as splash guards and see little water pass through them, although we like to see at least a little bit of water goes through them both for the cyclone effect as well as the percolation power.


Fritted Disc Percs


Fritted Disc Percolators are the kings of percolation power. There’s simply no other percolator that comes close to what a fritted disc can do. The number of bubbles, and therefore surface area of those bubbles, completely dwarfs all other percolators. Additionally, it has the durability and stackability advantages that all disc percolators have. However, there are two significant downsides that come with fritted disc percs. First is that the microscopic holes can be difficult to draw through because they create a lot of drag. Additionally, all those little pores can easily get clogged, meaning you’ll have to do maintenance more often than at least once every couple of weeks if you’re using it often. However if you don’t mind the drag, and you regularly clean your glass anyways, then this could be the perc to end all percs.


Spiral / Coil Percs


Coil / Spiral percolators are among the least talked about as well as the least understood. They are simply a coiled tube with a hole at the end, so what exactly makes this any different than a simple downstem? There are two main ways they differ from stems. First, the obvious difference is that they are more visually interesting. Glassblowing is an art, so many people look for aesthetics as much as function in their glass. The more useful difference is the length of the tube. Because the tube is coiled, you can coil 10″ / 25cm of tubing into a 2″ / 5cm vertical space. This forces the smoke to travel a longer path, increasing the cooling power of the percolator. However, when compared to other percs in terms of function, they aren’t nearly as effective. They may be better at cooling off a hit than most other percs, so if you value that over other features, you may like spiral percs. Or maybe you have 3 honeycombs and a fritted disc and you just want to add something different for your ashcatcher, then having a spiral could make sense. Although they aren’t our favorite percs on their own, they definitely have their place.


Faberge Egg Percs


Faberge percolators are another commonly misunderstood type of percolator. They are also similar to “Swiss” percs, which are basically flat sections of glass with large holes like swiss cheese. They don’t do anything on their own, but contrary to common beliefs, they do serve a functional purpose. They rely on being close to another percolator to work. In this video, the faberge percolator is coupled with a honeycomb percolator. When the bubbles rise up out of the honeycomb perc, the indentations on the glass split up the bubbles, thereby increasing their surface area and the filtration of the smoke. Swiss percs work the exact same way. Besides filtration, they are definitely meant to be decorative. It’s hard to compare to their style and elegance while also maintaining a functional purpose. This makes them an appealing option to anyone who places a real value on the aesthetics of their collection.


These are just the beginning!

The percolators listed here are by no means an exhaustive list. We assembled a list of the most common percolators, which share common designs with many percolators that aren’t listed here. For instance, there are probably 20+ variants of showerhead and tree percolators. After reading these, you should have an idea of the pros/cons to various percolator designs, and hopefully the information is general enough that you can make judgements on the designs of similar percolators that aren’t listed here. If you know of any substantially different than these, please share them with us, we’d love to hear about them. More importantly, to any glassblowers out there, keep on trying new things, we love to see new inventive ideas.