Radiators and hot water pipes get seriously hot, and ordinary wall paint simply isn't up to the job — it'll yellow, blister, and peel within weeks. Choosing the right heat-resistant paint and preparing the surface properly will give you a durable, good-looking finish that stands up to years of heating cycles.
Why Ordinary Paint Fails on Hot Surfaces
Standard interior paints are formulated for ambient temperatures. When applied to radiators or pipes that regularly reach 60–90°C, the resins in normal paint break down, causing discolouration, bubbling, and flaking. You need a paint specifically rated for high-temperature use. The good news is these products are widely available at NZ hardware stores and are straightforward to apply.
Choosing the Right Paint
Heat-Resistant Enamel (Most Common Choice)
For central heating radiators and hot water pipes, a heat-resistant alkyd or water-based enamel rated to at least 100°C is the standard go-to. These are available in a range of whites and off-whites — the most popular colours for radiators — as well as clear finishes. Brands stocked at Bunnings and Mitre 10 include specialist radiator enamels in both brush-on and aerosol formats.
High-Heat Paint (For Very Hot Surfaces)
If you're painting flue pipes, wood-burner surrounds, or surfaces that exceed 150°C, you'll need a high-heat or heat-resistant paint rated to 300°C or higher. These are typically solvent-based and often come in aerosol cans for easy application around awkward pipe shapes. They're generally available in black, silver, and a limited range of colours.
Water-Based vs Solvent-Based
| Feature | Water-Based Radiator Enamel | Solvent-Based High-Heat Paint | |---|---|---|| | Max temp rating | Typically 100–120°C | 200–600°C depending on product | | Odour | Low | Strong — ventilate well | | Clean-up | Water | Mineral turpentine | | Colour range | Wider (whites, creams) | Limited (black, silver, grey) | | Dry time | Faster | Slower | | Best for | Radiators, hot water pipes | Flues, fireplaces, exhausts |
Surface Preparation — The Most Important Step
No matter how good your paint is, a poorly prepared surface will let you down. Follow these steps:
- Turn off the heating system and allow the radiator or pipes to cool completely before you start.
- Clean thoroughly — remove dust, grease, and grime with a degreaser or sugar soap. Old radiators often have a build-up of oily residue.
- Sand lightly — use fine-grit sandpaper (around 120–180 grit) to scuff the existing surface and give the new paint something to grip.
- Treat any rust — if you spot rust spots, sand them back and apply a rust-inhibiting primer rated for metal before topcoating. Sika and other brands offer suitable metal primers.
- Wipe down with a tack cloth or damp rag to remove all dust before painting.
How to Apply Radiator Paint
- Use a small, quality brush (a 25–50 mm angled brush works well for radiators) or a short-nap roller for flat panel radiators. Aerosol cans are handy for pipes and awkward angles.
- Apply thin, even coats — two thin coats will always outperform one thick coat.
- Allow each coat to dry fully according to the manufacturer's instructions before applying the next.
- Some high-heat paints require a curing cycle — this means turning the heat on after painting so the paint hardens properly. Check the product datasheet for guidance.
- Ensure good ventilation, especially with solvent-based products. Open windows and use a fan if needed. WorkSafe NZ recommends adequate ventilation whenever working with solvent-based coatings.
Colour Considerations
White and off-white are the classic choices for radiators, and most radiator enamel ranges cater to this. If you want a bold colour, check that the product is specifically formulated for heat — some standard coloured paints won't cope. Resene can advise on suitable tinting options for heat-resistant bases, so it's worth calling into your local Resene ColorShop for advice.
What About New Radiators or Pipes?
Brand-new steel radiators and pipes often come with a factory primer coat. Lightly sand this, wipe clean, and apply your chosen heat-resistant topcoat directly. Galvanised pipes need a galvanised metal primer first, as standard primers and paints don't bond well to the zinc coating.
When to Call a Professional
Plumbing and heating work is restricted work in New Zealand. If your radiator or hot water pipe is leaking, corroded through, or needs to be moved or replaced, you must engage a licensed plumber or gasfitter — this is a legal requirement under the Plumbers, Gasfitters and Drainlayers Board (PGDB). Do not attempt to modify or repair pipework yourself.
Similarly, if your hot water system or heating boiler needs servicing, that's a job for a licensed professional. The painting itself is well within a capable DIYer's reach, but always make sure the system is fully isolated and cold before you pick up a brush.
If you'd prefer a professional painter to handle the job — particularly for older homes with complex radiator systems — you can find qualified local painters on tradedirectory.co.nz.