Cleaning Polywood Furniture with a Pressure Washer
Polywood (also called poly lumber or HDPE furniture) is a popular, low-maintenance alternative to painted wood for outdoor furniture. Its resistance to rot, insects and fading makes it an ideal candidate for routine cleaning with a pressure washer, but treating it incorrectly can leave streaks, gouges or damage. This guide covers safe settings, preparation, cleaning solutions, spot treatments, and aftercare so you can restore and protect your polywood seating, tables, and accessories.
What to know before you start
- Material properties: Polywood is a high-density polyethylene composite. It is durable but can be scratched by narrow, high-pressure streams.
- Test first: Always test any detergent, bleach solution or pressure setting on an inconspicuous area or the underside of a slat before treating entire pieces.
- Environmental care: Protect nearby plants and surfaces. If you keep organic waste nearby-such as using the best worm bin for indoor composting-move it away to prevent chemical runoff and odor transfer during cleaning.
- Other items: While you clean furniture, you may also clean planters and hardscapes. For example, methods for cleaning mineral buildup from glazed ceramic pots differ from polywood care; plan separate treatments to avoid cross-contamination.
Tools and supplies
- Pressure washer with adjustable pressure (electric or gas)
- Nozzles: wide-angle / fan nozzles (25°–40°). Avoid 0° or narrow pencil jets.
- Garden hose for pre-rinse
- Mild detergent formulated for plastics or a biodegradable, phosphate-free cleaner
- Oxygen bleach (sodium percarbonate) for organic stains and mildew; household bleach (sodium hypochlorite) used cautiously and diluted where necessary
- Soft bristle brush or nylon scrubbing pad and a spray bottle for spot treatments
- Personal protective equipment: eye protection, gloves, and footwear
Pressure washer settings and nozzle selection
Polywood responds best to moderate pressure and a gentle spray pattern:
- Pressure: Aim for 1,200–1,800 psi for most cleaning tasks. Stay below 2,000 psi unless directed by the furniture manufacturer.
- Nozzle: Use a 25° or 40° fan nozzle to distribute force over a wider area and avoid etching the surface.
- Distance: Maintain a working distance of 12–24 inches from the surface. Closer distances increase risk of damage.
- Motion: Keep the wand moving in smooth, overlapping passes. Never linger in one spot.
Step-by-step cleaning process
- Clear and prep: Remove cushions, accessories, and planters. Sweep away loose debris and rinse the furniture with a garden hose to remove surface dirt.
- Pre-treat stains and organic growth: For mildew, algae or stubborn organic staining, apply an oxygen-bleach solution (follow label dilution) with a sprayer or sponge and allow 10–15 minutes to dwell. For small concentrated spots, use a soft brush. If you opt to use household bleach, dilute to about 1:10 (household bleach:water), rinse plants and soil away beforehand, and never mix bleach with ammonia or acidic cleaners.
- Apply detergent: Use a plastic-safe detergent in the washer's soap tank or apply by hand. Let it sit a few minutes but do not allow cleaners to dry on the surface.
- Pressure wash: Using the 25°–40° nozzle, rinse from top to bottom in overlapping passes at the recommended distance. Keep the wand moving and avoid narrow-angle nozzles. If the washer has an adjustable PSI, start low and increase only if needed.
- Rinse thoroughly: Remove all detergent and residue with clear water; trapped cleaner can leave hazing or attract dirt more quickly.
- Spot treat remaining stains: For grease or ink marks, use a small amount of isopropyl alcohol on a cloth and blot-test first. For deep-set mildew, reapply oxygen bleach and scrub lightly, then rinse.
- Dry and reinstall: Allow pieces to air dry fully before replacing cushions. Polywood dries quickly and will not warp like wood.
Dealing with specific problems
- Mildew and algae: Oxygen bleach is preferred-effective and less corrosive. Apply, let sit, scrub lightly, and rinse. For persistent spots, a diluted household bleach solution can be used briefly with careful rinsing and plant protection.
- Oil, grease and food stains: Use a degreasing dish soap or a solvent-free cleaner. Apply, let sit, then scrub with a nylon pad and pressure-rinse.
- Color fading and surface chalking: Polywood can fade over time from UV exposure. Cleaning won't restore pigment but removes chalky residue. If desired, use a plastic-restoring product recommended by the manufacturer-apply according to instructions.
- Rust or metal staining: Clean any metal hardware separately. If metal stains have transferred, try a mild acid rinse (diluted white vinegar) on a test spot, rinse promptly, and avoid prolonged contact.
Tip: If you're unsure about pressure, start with the widest nozzle at the lowest effective pressure and a distance of 24 inches-then gradually move closer until you get a clean surface without damage.
Safety and environmental considerations
- Protect plant life and pets by wetting down nearby soil before cleaning and covering delicate foliage. Neutralize and dilute any bleach runoff with plenty of water.
- Use biodegradable, phosphate-free cleaners where possible to reduce impact on storm drains and soil. Avoid solvent-based strippers or abrasive chemicals that can harm plastics or surrounding materials.
- Wear gloves and eye protection when handling bleach, oxygen bleach, or concentrated detergents.
Maintenance schedule and tips
- Routine rinse: Rinse with garden hose monthly to prevent buildup of grime and pollen.
- Deep clean: Pressure wash and treat mildew or stains once or twice per season depending on exposure and local climate.
- Store cushions indoors when not in use to reduce staining and odor transfer; zippered covers make this easier.
- Inspect hardware seasonally and tighten or replace as needed to avoid metal corrosion or staining.
Cross-topic practical notes
When cleaning your outdoor seating, you might also be caring for pots and nearby potted plants. Techniques differ: cleaning mineral buildup from glazed ceramic pots often requires soaking with vinegar or using a lime-removing product, whereas polywood benefits from oxygen bleach and low-pressure rinsing-keep treatments separate to avoid unintended reactions. Likewise, if you're tending houseplants or orchids on the patio, understanding potting choices matters. For instance, gardeners often weigh the pros and cons of how to repot orchid in bark vs moss; bark provides superior drainage for many epiphytic orchids, while moss retains moisture-neither approach should be subjected to harsh runoff from cleaning chemicals that could harm roots after repotting.
With careful preparation, moderate pressure settings, gentle detergents, and attention to plant and environmental safety, pressure washing is an efficient and safe way to keep polywood furniture looking fresh year after year.
More tips in the section Botanical Vitality & Outdoor Infrastructure