Is Glass Silicone Safe for Drinking Water?
Is Glass Silicone Sealant safe in contact with drinking water?
No. Selleys holds no certification to AS/NZS 4020 stating that Glass Silicone Sealant is suitable for contact with drinking water. It should not be used on a rainwater tank, a potable water line, or anywhere that water people drink will touch the sealant.
There are products in the Selleys range that are approved for it. Roof & Gutter Silicone and Roof & Gutter Speed Seal both meet the drinking water contact standard. Roof & Gutter Spray Seal meets it too.
What AS/NZS 4020 actually is
AS/NZS 4020 is the Australian and New Zealand standard for testing products used in contact with drinking water. Its full title — Testing of Products for Use in Contact with Drinking Water — describes what it does: it tests whether a material affects the water it touches, covering taste and odour, the growth of microorganisms, the leaching of metals, and the extraction of other substances.
This is why "it's a food-safe-looking clear silicone" is not an answer, and why "it doesn't dissolve in water" is not an answer either. The standard is about what the material gives up into the water over time, and that can only be established by testing it.
A product either has that testing behind it or it does not. Glass Silicone does not. Roof & Gutter Silicone's technical data sheet lists AS/NZS 4020:2018 under Standards and Conformities.
One important caveat on the approved products
Roof & Gutter Silicone is supplied in a wide range of Colorbond-matched colours, and its technical data sheet carries this note: not all colours have been tested for AS/NZS 4020:2018. Current test reports are available on request.
So if the joint is genuinely in contact with drinking water — the inside of a tank, or a fitting on a potable line — do not assume every colour in the range carries the approval. Ask Selleys for the current test report for the specific colour you intend to use, on 1300 555 205.
The products compared
| Property | Glass Silicone | Roof & Gutter Silicone | Roof & Gutter Speed Seal |
|---|---|---|---|
| Drinking water standard | No AS/NZS 4020 certification | AS/NZS 4020:2018 (not all colours tested) | Meets AS/NZS 4020 |
| Cure chemistry | Acetic cure silicone | Neutral cure, 100% silicone | Neutral cure, 100% silicone |
| Skin time | 5–10 minutes (weather dependent) | 5–10 minutes | — |
| Cure rate | 2mm per day; cures in 72 hours | 2mm / 24 hours | Rain-ready in about 1 hour |
| Service temperature | −60°C to +150°C | −60°C to +150°C | — |
| Joint movement | ±25% | ±25% | — |
| Aquariums | Suitable, with a 7-day cure and a wash-out before stocking | Not stated | Not stated |
Indicative data only, not intended for the preparation of specifications.
Why "safe for aquariums" is not the same as "safe for drinking water"
This trips people up regularly, because Glass Silicone is the Selleys product for aquariums. Its technical data sheet says so: it is suitable for constructing and repairing small aquariums, allow 7 days cure, then thoroughly wash the tank out with water, drain and refill before introducing fish.
Those are two different questions. An aquarium is a body of water that gets flushed, filtered and topped up, and the fish live in a managed system. Drinking water is consumed directly, and the AS/NZS 4020 tests exist to establish what a material does to water that people will drink. Passing one does not imply passing the other, and Selleys does not claim it does.
What else in the range carries drinking water approval
Selleys Knead It Aqua epoxy putty complies with AS/NZS 4020 for contact with drinking water at temperatures up to 85°C. That is a different kind of product — a rigid repair putty rather than a flexible sealant — but it is the one to look at for plugging or rebuilding rather than sealing a joint.
By contrast, the wet-area silicones are explicitly excluded. No Mould, Wet Area Silicone and Wet Area Matt Silicone all state they are not suitable for food or drinking water contact.
Limitations of Glass Silicone worth knowing
- No AS/NZS 4020 certification — not for drinking water contact.
- Not recommended for use on concrete, cement products, zinc, or metals containing copper.
- Not recommended for below-waterline applications, glass aquariums excepted.
- Not for mirrors — Selleys directs you to Liquid Nails Mirror & Metal instead.
- Not paintable. Complete painting 7 days before applying the sealant.
- Store below 30°C in a dry place; use within 6 months of opening.
Common questions about sealants and drinking water
Can I use Glass Silicone on a rainwater tank?
Not where it will contact the stored water. Use a product with the AS/NZS 4020 approval, and confirm the specific colour is covered.
Which Selleys product should I use on a water tank joint?
Roof & Gutter Silicone or Roof & Gutter Speed Seal, subject to the colour caveat above. Both are neutral cure, 100% silicone.
Does neutral cure make a sealant drinking-water safe?
No. Neutral cure means the sealant does not release acetic acid as it sets, which matters for metals and stone. Drinking water suitability is established by AS/NZS 4020 testing, which is a separate matter entirely.
Is Glass Silicone safe for a fish tank?
Yes, with conditions — 7 days cure, then wash the tank out thoroughly, drain and refill before adding fish. Selleys notes it suits constructing and repairing small aquariums, and that large tanks need specialist design.
What about the outside of a tank, away from the water?
A joint on the outside of a tank that does not touch the stored water is an ordinary weather-sealing job, and Roof & Gutter Silicone suits it well.
How do I get the test report for a particular colour?
Contact Selleys on 1300 555 205 and ask for the current AS/NZS 4020:2018 test report for that colour. The technical data sheet states these are available on request.
Is Roof & Gutter Silicone suitable for permanent immersion inside a tank?
No. Its technical data sheet says it is not recommended for continuous submersion or below-waterline use. It is approved for drinking water contact, which is a different condition from being permanently under water.
What about stainless steel tanks and gutters?
Roof & Gutter Silicone lists steel and stainless steel among its suitable non-porous substrates — see sealing stainless steel gutters.
Is Selleys Glass Silicone safe for use with drinking water?
No, Selleys Glass Silicone products are not recommended for drinking water applications. Specifically, Selleys Glass Silicone - 310g Cartridge is not suitable for potable water contact and is designed instead for general glazing and sealing applications on windows, frames, light fittings, skylights, glass, and ceramics.
What product should be used instead if drinking water contact is required?
PRO-TRADE Glass Sealant should be used instead, as it is suitable for potable water sealing applications and is certified as meeting AS4020 standards (Testing of Products in Contact with Drinking Water).
What standard certifies a sealant as safe for contact with drinking water?
AS4020 is the standard for Testing of Products in Contact with Drinking Water, and PRO-TRADE Glass Sealant is certified as meeting this standard.
What applications is Selleys Glass Silicone - 310g Cartridge designed for?
It is designed for general glazing and sealing applications on windows, frames, light fittings, skylights, glass, and ceramics—not for applications involving drinking water.
What steps should be taken before using a sealant in an application involving drinking water?
You should use PRO-TRADE Glass Sealant, which is certified for potable water applications, always verify the product label and Safety Data Sheet before application, and ensure the specific product variant selected is rated for drinking water contact.
Who publishes this expert advice page on glass silicone and drinking water safety?
The page is published by Selleys, an Australian adhesives, sealants and fillers brand founded in 1939 in Sydney, Australia by Martin Selley, and now a division of DuluxGroup (Australia) Pty Ltd.