Is PVC Safe For Hydroponics? Truth or Myth?


PVC pipes are a reliable, common, and preferred material in almost every hydroponic system. However, is there a looming threat to your health and to your garden in continually using them?

PVCs are safe for hydroponics. These compounds have been tried and tested. However, the PVC to adopt for hydroponic applications should be rigid or unplasticized. This makes them food safe since they would not have BPAs or phthalate.

But there is more to this than just going out and buying the first PVC pipe you see. Some of them might not be suitable for you as PVC presents different nuances.

Is PVC Plastic Safe For Hydroponics? Here the Truth

PVCs are very stable compounds which have a host of useful properties ranging from resistance to insulation. The fact that they are plastics does not ipso facto render them unviable. Unplasticized PVCs are considered food-safe plastics which means that will pose no health risk to humans and plants.

PVCs Pros in Hydroponics?

PVCs are so commonly used in hydroponics because they are 1) cheap, 2) easily available and 3) easy to cut.

Other pipe materials such as stainless steel, copper, ceramic, or galvanized would be too cost-prohibitive for small or large-scale hydroponics setups.

PVCs have good rigidity, flexibility, chemical resistance, oxidation resistance, sunlight resistance, electrical insulation, and thermal insulation. Due to these properties, PVCs are widely used for domestic, commercial, and industrial applications.

They can be easily sawed and reconfigured depending on the system. As such, many hydroponic gardeners use PVCs to good effect, producing healthy plants with high yield – from hobbyists, small scale producers, to large industries, PVCs are a common sight. The inference is that if it’s safe for drinking water, then it must be safe to implement in a hydroponics system.

PVC Composition and Types

PVC (polyvinyl chloride) is synthetic plastic polymer and the third most widely produced of its kind in the world. PVCs are made of rock salt and natural gas which undergo a process of heating, electrolysis, polymerization, melting, and shaping. They are listed Recycle Number #3 under the seven standard classification for plastic reuse. PVCs, as previously mentioned, have a bouquet of properties which make them attractive to use.

However, not all PVCs are created equally. They come in broad categories of either (1) rigid or (2) flexible.

There are 5 main types of PVC:

  • PVC-P (plasticized PVC) is a flexible PVC made flexible and durable by incorporating plasticizers. These PVCs have Bisphenol A (BPA) and phthalates.
  • PVC-U (unplasticized PVC) is a rigid PVC without any plasticizers. Safe for drinking water and are often the safest choice for transporting water. These neither have BPA or phthalates and are used for residential and commercial purposes.
  • C-PVC (chlorinated PVC) similar to PVC-U in terms of properties but has higher chlorine content, greater heat resistance, and greater ductility. Often used for residential drinking water. It is more stable.
  • PVC-O (molecularly oriented PVC) is essentially an enhanced PVC-U, increasing its resistances across the board.
  • PVC-HI (high impact PVC) is industrial grade PVC which blends different polymers to make the most resistant and durable type of PVC. These are often used for transporting natural gas.

Which PVC Types Are Hydroponic Safe?

Modern PVC pipes are very safe for use in hydroponics.

Hydroponics systems commonly use PVC-U and C-PVC because they have been tried and tested by different standards organizations such as the US EPA, NSF International, American National Standards Institute (ANSI), American Water Works Association (AWWA), and ASTM International.

For our purposes, PVC-U and C-PVC are our best bets because of their safe properties and their wide availability.

  • Use PVC-U or C-PVC. Though there are better types of PVCs, these are more suited to industrial applications.
  • C-PVC is inherently inert. It is more resistant to most salts, acids, and bases which makes it suitable to transport hydroponic nutrient solution.
  • Look for Schedule 40, NSF-61, NSF-PW markings in PVC pipes. These are safe for both hydroponics and aquaponics.

PVC-U and C-PVC can be easily differentiated based on the manufacturer’s marking. These are often seen on the end of the pipes and are printed in black.

It is important to note that these PVCs have been used not only North America but the rest of the world.

Furthermore, unplasticized PVCs fall under Recycle Number #3 which are plastics which are considered food-safe plastics. The other being Recycle Number #2 and Recycle Number #5.

Additionally, since hydroponics use PVCs in a controlled condition whereby water temperature, pressure, composition, and acidity are not meant to deviate, there are less factors to consider. PVCs’ use for water consumption have far more factors to take into consideration whereby extra steps are taken.

Will PVCs in Hydroponics Affect My Plants?

As stated previously, BPA and phthalate will not be taken in by the plants if the PVC does not have plasticizers. The Vinyl Chloride Monomer (VCM), thought toxic and harmful to the health, are only present during the manufacturing process of PVCs and not in the PVC itself.

Dioxins, (Polychlorinated dibenzodioxins) are only present if the PVCs are burned and even then PVCs have good heat resistance and are flame retardant. Likewise the chlorine that makes up 57% of PVC composition is safe. The chlorine used in PVC is highly stable and will not produce chlorine gas.

Hence, none of these harmful substances will be absorbed by the hydroponic plants nor by the people consuming said plants.

Then why is there misinformation?

First and foremost, the conflicting reports online whether they are safe or unsafe stems from the lack of understanding of the differences between rigid and flexible PVC and which types of PVCs are being used hydroponics.

The main problem is that scientific data used by many sites do not nuance between the two. Simply put, PVCs without plasticizers are free from BPA or phthalates and are considered food-safe. Due to this fact, plants in a hydroponics system will not uptake these chemicals. There is a manifest lack of nuance in understanding the chemicals, their source, and their effect in the chain.

Protecting PVC from Heat and UV Light

PVCs, though a stable substance, may leach out chemicals such as under very high temperatures. The maximum operating temperature of ~60°C (140 °F). It begins to warp at these temperatures. This should be of no concern since warm water is not used in hydroponics as it would kill the plants. Additionally, since water is constantly being recirculated in a hydroponics system, the water temperature would be regulated.

Additionally, UV light may cause leaching. Light may produce algae or other microorganisms in the water.

For example, Schedule 40 PVC pipes are often white, hence do not block out light as well which may lead to biofilm accumulation or leaching. As such, hydroponic gardeners and producers recommended painting PVC pipes to give them more protection against heat and UV rays. This is not just a common practice in hydroponics but in irrigation, plumbing, and construction as well.

Replacing PVC with Organic Material

It is also possible to replace PVCs with organic materials such as wood or bamboo. The difficulty comes in sawing and fitting them into the desired shape, length, and width as they are not uniformly shaped unlike PVCs. It is also important to consider that they may be more expensive depending on which part of the world you’re in.

Other Miscellaneous Concerns

Fittings are likewise safe as long as they do not have plasticizers. Teflon tapes used to seal pipe fittings are inherently non-toxic.

More Knowledge: If you want more information regarding plumbing product marks, the NSF has a simple guide to inform consumers on the matter. Different markings denote different physical properties and certifications.

Replacing PVC with Non-Plastic Materials

Though very expensive, copper pipes are a possible alternative. Copper pipes have been the standard in hot and cold drinking water delivery. They are antimicrobial and antibacterial.

To watch out!

Copper itself may kill beneficial bacteria and microbes which are conducive for plant growth. Additionally, copper is not recommended for aquaponics because its properties may kill hatchlings of snails, frogs, fishes, and etc. The same can be said with galvanized or stainless steel pipes depending on their specific manufacturing process.

Ceramics are an environmentally friendly option since these are only made from water and clay. If produced properly, they will not leach. However, you do give up durability since ceramics are inherently brittle

Takeaways

  1. Unplasticized PVCs are worthy for drinking water transportation and application in hydroponics. They will not negatively affect the plant or the
  2. They are stable compounds given a bad reputation due to the lack of nuance in discourse.
  3. Though there may be alternatives, PVCs offer a cheapest, simplest, and safest solution.

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Sources

“7 Myths About PVC – Debunked” by John Wagner in Carlisle Syntec

“A review on the durability of PVC sewer pipes: research vs. practice” by Makris et al in Structure and Infrastructure Engineering

“Antimicrobial properties of a novel copper-based composite coating with potential for use in healthcare facilities” by Montero et al in Antimicrobial Resistance & Infection Control

“Emission of phthalates from PVC and other materials” by Afshari et al in Indoor Air 14(2)

“How to Tell If Plastic is Safe for Hydroponics/Soil (Indoor Gardening)” by Growing Answers

“Frequently Asked Questions on Health Effects of PE Pipe and Fittings” by n/a in NSF International

“Phthalates | Assessing and Managing Chemicals Under TSCA” by n/a in EPA.

“Plumbing Product Markings” by n/a in NSF International

“POLYVINYL CHLORIDE (PVC)” by n/a in PPFA

“PVC SCHEDULE 40 PIPE” in PVC Pipe Supplies

“Ullmann’s Encyclopedia of Industrial Chemistry” by Michael Allsopp and Giovanni Vianello in Wiley Online Library

“Uptake and Metabolism of Phthalate Esters by Edible Plants” by Sun et al in National Library of Medicine

Andrea

A young Italian guy with a passion for growing edible herbs. After moving to the UK 6 years ago in a tiny flat, it was impossible to grow herbs outside. So I start my journey in growing indoor and so I decided to share my knowledge.

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