PET Bottle Hydroponics Kit — Net Pot + Snap Caps for 28 mm & 38 mm Bottles (Kratky)

Grow fresh herbs on your windowsill from bottles you'd otherwise recycle.

This set turns an ordinary PET drink bottle into a passive hydroponic planter using the Kratky method — you fill the bottle with nutrient solution, drop in the net pot with a seedling, and the roots grow down into the water. No pumps, no power, almost zero maintenance.

It was designed around real, measured bottle necks so the parts actually fit — not a generic model that's "close enough."

What's included (3 STL files)

• Net pot / basket — universal, slim Ø19.5 mm body that drops through both neck sizes. Holds a standard 16 mm grow plug / sponge holder on an internal seat (it won't fall through), with a Ø13 mm root channel and 6 side windows so roots reach the water and get oxygen.

• Cap — 28 mm neck — fits the most common PET bottles (water & soda, PCO‑1881 standard, e.g. Mattoni Essence and similar). Push‑on fit.

• Cap — 38 mm neck — fits wide‑mouth bottles (iced tea / juice, e.g. Nestea and similar).

The net pot sits in the cap; the cap pushes onto the bottle. Same net pot works with either cap.

Why you'll like it

• ♻ Upcycles bottles you already have — basically free planters

• 🔌 No electricity / no pump — true passive hydroponics

• 🌱 Great for basil, lettuce, mint, parsley, cilantro and other leafy herbs

• 🧩 Two neck sizes covered with one shared net pot

• 🖨 Fast, small prints — no supports

What you'll need (not included)

• A clean PET bottle (28 mm or 38 mm neck)

• A 16 mm net/grow plug holder + rockwool or sponge (or just sponge)

• Hydroponic nutrient solution + seeds

PRINT SETTINGS

• Material: PETG recommended (durable, holds up to constant moisture). PLA is fine for trying it out.

• Layer height: 0.20 mm (0.16 mm for a cleaner net pot)

• Walls / perimeters: 3

• Infill: 15–20 %

• Supports: None — the net‑pot windows and caps print support‑free

• Orientation: Net pot flange up; caps with the open skirt down on the plate

• Print time: ~15–35 min per part

Fit tip: the caps are a push‑fit. If your bottle's neck is slightly different, scale the cap by 1–2 % or sand the inside. Bottle necks vary a little between brands — measure your neck's outer thread diameter with calipers if unsure (≈28 mm or ≈38 mm).