Grommets are used to create watertight seals for the plumbing of hydroponic systems such as NFT systems, DWC systems, Dutch Bucket systems, water reservoirs etc.
A hole is drilled and the Grommet is inserted into the hole. Piping is then pushed through the grommet which will form a watertight seal.
Product Specs
Irrigation Piping, Ring Grommet and Top Hat Grommet measurements follow below:
Grommet Sizes
| Size Irrigation Piping | Size Ring Grommet | Size Top Hat Grommet |
| 5mm | 6mm | 6mm |
| 12mm* | 12mm / 15mm * | 16mm |
| 15mm | 20mm | 19mm |
20mm irrigation piping: –
25mm white PVC electrical conduit: 25mm Ring Grommet
Hole Saw Sizes for Grommets**
| Size Ring Grommet |
Hole Saw Size |
Size Top Hat Grommet | Hole Saw Size |
| 6mm | 9mm drill bit | 6mm | 9mm drill bit (very tight fit) or 10mm drill bit |
| 12mm | 19mm | 16mm | 19mm |
| 15mm | 19mm | 19mm | 21mm |
| 20mm | 25mm | ||
| 25mm | 31mm | |
* 12mm irrigation piping:
- 12mm Ring Grommet fit will be a very tight fit, while a 15mm Ring Grommet’s fit could be a little loose
- This could be countered by using an insert fitting (eg. straight connector/T-piece/elbow) inside the piping at the point where it goes through the grommet, to flare out the piping and create the waterproof seal.
** Hole Saw Sizes:
- These hole saw sizes are for flat surfaces, not for curved surfaces.
- A slightly smaller hole can be tried on curved surfaces to prevent possible leakage due to the curving of the grommet on the curved surface.
- Drilling test holes and testing if seals are watertight is always advised.
Please Note:
- It is not recommended that Petroleum Jelly is used as a lubricant. A silicon lubricant, although more expensive, is better. Olive oil can also be used.
- If grommet is fitted and then taken out a number of times, it may stretch and warp.