Is Bong Water Good For Plants?

Is Bong Water Good For Plants

Reading Time: 8 minutes 🍃

With the world increasingly aware of the value of a circular economy, every vein of life has people looking for opportunities to reduce, reuse and recycle things they come across in their daily lives, which would normally end up as waste. It’s no surprise, then, that if you’re a regular smoker, you might have wondered whether you could make use of your bong water in the garden — but is bong water good for plants?  

Bong water is not good for plants. While it contains a number of plant derivatives, there are many chemical compounds that can cause stunted growth in plants. This means that in almost no circumstances is using bong water in the garden appropriate.

This might seem counterintuitive when so much considering how natural the weed being smoked is. Keep reading to understand more about why bong water isn’t good for plants.

Why Is Bong Water Not Good for Plants?

To really understand why bong water is not good for plants, we have to understand what the purpose of the bong water is and what that means for its composition.

Water bongs date as far back as 2,400 years ago, with the waterpipe being documented in 17th century India by a physician named Hakim Abul Fath, who believed that smoking tobacco through water would remove any dangerous properties.

Since then, the usage has evolved over time, but when used to smoke cannabis, the method is largely the same — the smoke drawn from the burning of the cannabis (sometimes mixed with tobacco, depending on the region) is drawn through the water in the bong. This is often completed in two steps:

  • Consistent drawing of smoke through the water, collecting in the bong
  • The inhalation of the collected smoke

These steps also contribute to the contaminants that remain in the water, as there is a prolonged period of contact with the user’s mouth during the first step.

The drawing of the smoke through the water not only allows the water to cool the water down, making the ultimate inhalation more comfortable for the user, but the water also serves to trap heavy and water-soluble molecules. 

This process results in many different substances being present in the bong water when it is usually considered to be in a finished state, a point at which point a user would usually consider disposal.

Some of the most commonly found chemicals within used bong water are shown below:

  • THC
  • CBD
  • Tar, including Polycyclic aromatic hydrocarbons
  • Ash
  • Naphthalene
  • Acrylamide
  • Acrylonitrile 
  • Carbon monoxide
  • Carbon dioxide


THC is one of the most famous components of cannabis, mostly as a result of it being the main psychoactive component of the drug. Its scientific name is tetrahydrocannabinol, and it binds to the cannabinoid receptors in the brain, causing the famous ‘high’ feeling associated with smoking cannabis.

There is little to no formal research on the impact of THC on plant growth, and while it does not at the current time have any association with stunted growth, it also has no known positive effects.


CBD is the acronym for cannabidiol, another common compound heavily associated with the positive effects of cannabis usage. This is because while CBD has no link to the euphoric feeling of being high, it does play a broader role in a feeling of well-being. For this reason, it is increasingly used as a reliever of pain and is prescribed for human use for a number of different conditions, such as:

  • Arthritis
  • Crohn’s disease
  • Diabetes
  • Multiple sclerosis

The research here is still in its early stages, but it has already been shown to reduce the number of seizures in patients with epilepsy.

It is thought that — similar to THC — CBD does not make a difference to plant growth, either positively or negatively.


Tar is the first major component of bong water which we know will have a detrimental effect on plant growth. This is because its properties restrict the ability of the soil structure to behave naturally, which in turn can inhibit the level of nutrient uptake by the plants. There is also research that suggests that tar impacts the photochemistry of plant cells, further stunting growth.


Naphthalene is an aromatic hydrocarbon made of two fused benzene rings. Despite actually occurring in the essential oils of many plant species, that doesn’t make it a good addition to the soil as a fertilizer. 

It has been shown to increase the number of fatty acid peroxides, and while the impact on the plant is limited, it still will mean the chemistry of the plant’s normal growth is changed in ways that do not benefit growth. 


Acrylamide is an organic compound that forms as a result of high-temperature reactions, in the case of bong water, as a result of the burning of cannabis. Acrylamide is known to be highly mobile, being able to degrade under a few types of mechanisms. This can lead to the release of acrylamide monomer, which is a toxic substance (and possible carcinogen) and another reason that plant growth can be impacted.

Other Problems

The main reason why bong water is not good for plants is a result of all of the different things that end up in the water over time. Bong water has been through long exposure to smoke produced by the burning of cannabis and any other substances used and is also heavily exposed to the users’ breath during this process, meaning it can also contain bacteria and viruses that the user themselves introduces.

Bacteria and viruses can also be very detrimental to the growth of plants. As there are so many different types of bacteria and viruses present in the soil already, it’s very difficult to know what impact those that are present in bong water as a result of ongoing use are likely to do. It does, though, present one more risk that is even more reason to steer clear of bong water as a fertilizer.

As if we needed another reason after all of the above, there is one more to add to the list. Bongs are made from a number of different materials, the most common being glass and plastic. While glass bongs are typically more reliable, if a bit more fragile than their plastic counterparts, they have been shown to be relatively robust. The same cannot be said for plastic bongs, though. 

Some research has shown that plastic bongs which are exposed to heat or sunlight can, over time, have plastic leech into the water in the bong as a result of chemical processes occurring within the plastic.

It’s clear that the reason plants don’t like bong water is that it contains a whole host of chemicals to which plants do not respond well. As a result, you should never apply bong water on or around a plant if you want it to grow effectively.

You can see the opinion of a soil scientist on the impact of bong water here. 

Does Bong Water Affect Soil pH Levels?

The many contaminants within bong water that it captures during the filtration process mean that it usually ends up with a fairly acidic pH. This means that applying bong water to the soil, aside from the negative impact it can have on soil structure and if the plant absorbs it, will also render the soil more acidic.

Every plant has a range of different nutrients it requires in different amounts. This nutritional uptake is in part determined by the pH level of the soil, which measures how acidic or basic the soil is. 

When a plant is being grown in a soil bed that does not have the required pH levels, in practice, this means that the soil’s acidity is not conducive to the nutritional requirements that the soil has. This can often result in stunted growth as a result of the deficiencies (and sometimes toxicity) that an inappropriate soil pH can cause.

Therefore, another important concern if you are planning on or have already applied bong water to the soil is the impact it could have on the pH levels of the soil bed. This will depend a great deal on the plants within the bed and their preferred pH levels, which are often the result of the general soil quality in the areas in which they are natively found.

Some examples of plants that prefer acidic soil are:

  • Rhododendrons
  • Azaleas
  • Camellia

Whereas some of those that prefer the soil to be more alkaline are:

You may find that if bong water is applied only in a specific area, assuming it is a low volume of liquid and poured out of the bong, it will disproportionately affect a single area, which could, in turn, require remedial action to either undo the impact on the pH levels, or at least balance out the change across the soil bed.

If bong water has caused an acidic build-up in the soil, then a process called liming will be required in order to neutralize the acidic compounds that have been introduced. In either case, it is recommended that gardeners use test kits — either commercial or homemade — in order to gain an accurate picture of the pH levels across the soil bed before making significant changes that could otherwise cause unforeseen problems.

Can Cannabis Ash Be Used in Compost?

While bong water might be terrible for the garden, what about the ash that comes from the burning of cannabis? This ash is similar to the ash of other plants but isn’t quite the same, so the answer to this question breaks down into two different parts:

  • The role of ash in compost
  • Is cannabis ash suitable

The Role of Ash in Compost

Ashes are a common addition to compost due to the levels of potassium and calcium they can often contain. They can be a useful addition to the compost pile by balancing some of the more nitrogen-heavy additions that are made over time. The ash that is used more frequently is wood ash, but all ash from plant material shares many properties.

Having said that, ashes tend to be added relatively infrequently so as not to overwhelm the current pH levels of the compost with a large volume of heavily alkaline material. All composting also requires time for the material to break down and can benefit from regular mixing and turning in order to get ensure that all the rich components within the compost are balanced throughout the load.

It’s also worth bearing in mind that if compost has had a lot of ash added over time, you may want to test the level of acidity prior to applying it to the soil in order to avoid any issues with heavily alkaline compost altering the pH levels of the soil beyond the range that is suitable for the plants there.

Is Cannabis Ash Suitable for Compost

The issue that faces cannabis ash is that more than many other types of ash, such as wood ash, it is more likely to contain chemical compounds which have a negative effect on the soil quality. This is because, by its very nature, the burning of cannabis releases more chemicals and tar, which might be a bad decision for the quality of the compost.  

Therefore it required a great deal of thought before adding cannabis ash to the compost pile. In all likelihood, different ash types would be preferred — especially the more common wood ash. This is because it controls the amount of negatively impacting material present within the end product. If you have no other options, want the compost pH to change, and are comfortable with the contaminants that will also make their way into the compost, then it can be considered.


It’s clear that while it might be a nice idea, in practice, using bong water in the garden is likely to leave you very disappointed. Worse, it might actually damage the plants you’re trying to help, so users would be best advised to tip away the used bong water and stick with other solutions in the garden.


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