Hydroponics workshop: Plastics and alternatives

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Materials (ref1, ref2):

It’s important to think about the materials which will be in contact with your nutrient solution. Some concerns are:

  • Will it leech chemicals into the water?
  • Is it UV stable or will it break down and become brittle under light?
  • Is it an organic material which can rot or mold?

About plastic: There are a lot of different types of plastic. Do a little reading and decide for yourself what you’re comfortable with, and pay attention to the markings when buying plastics. You have to decide for yourself, but here’s my opinion:

Okay for hydroponic applications: 1: PET – think pop bottles, ketchup bottles2: HDPE – think milk jugs, ice cream pails (NOTE: Lots of food grade plastic Is HDPE, but not all HDPE is food grade. Use HDPE reclaimed from food packagine or bearing a food grade marking.)

4: LDPE – some squeezable bottles, some frozen food bags

5: PP – some yogurt or margarine tubs

Should be avoided (but still very widely used in homemade systems): 3: Vinyl and PVC leach chemicals (including a suspected carcinogen) into the water as they age or as they are exposed to the sun.  PVC is very commonly used in NFT systems, so this is surprising news.6: Polysterene – used for styrofoam rafts, manufactured using a known carcinogen and contains suspected carcinogens.

7: Other – best assume the worst

What about 3D printable materials?

PLA (polylactic acid) is biodegradable, in fact it’s used to make surgical implants which will slowly dissolve into the body, since PLA biodegrades into lactic acid which the body processes. Harmless to people doesn’t necessarily mean harmless to plants, but I did find reference to lactic acid being considered environmentally safe.

PLA for inside a hydroponic system would be best bought in ‘natural’ colour (ie, undyed). Note: 3D printed PLA is porous and conceivably could harbour bacteria. Delicate items like net cups could become brittle and break over time.


Nylon – unknown, but nylon has a flexibility and strength that could potentially make great net cups.


Other materials:

Glass: no problem, just remember to lightproof

Wood: good for support structures, but avoid exposure to nutrient solution. Untreated wood will rot in water or mold in humidity, and treated wood raises concerns about the treatment chemicals.

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