A bathroom can look stunning, but if the drainage is poor, it won’t feel like a success. Slow-draining water, gurgling pipes, or unpleasant smells can quickly undo all your hard work. Drainage plays a bigger role than most people realise, and it’s especially important to get it right when planning a renovation. The good news is that with a few checks and the right advice, you can avoid costly mistakes and keep your bathroom running smoothly.

1. Know the signs of good drainage

Good drainage should be fast, quiet, and odour-free. Showers, basins, and baths should empty quickly, while toilets should flush without gurgling. Traps beneath each fixture hold a small amount of water to block sewer smells. If your drains are slow, noisy, or smell musty, call in a plumber before starting renovation work.

2. Inspect your existing system

Before making changes, check what’s already in place. Look under the house or in service areas for leaks, damp soil, rusted clips, or sagging pipes. Watch for mismatched pipe materials or flexible hoses being used permanently. Spotting these problems early helps prevent disruption once walls and floors are opened.

3. Make sure pipes have the right fall

Drainage relies on gravity, so pipes need the correct slope, known as fall. If they are too flat, too steep, or full of sharp bends, wastewater may build up and cause blockages. Ask your plumber to confirm that traps hold the correct water seal and that all waste lines slope properly.

4. Factor in upstairs bathrooms

Renovating a bathroom on an upper floor can be more complex. New drainage lines may need to be routed through walls or ceilings below, and in some cases a pumped waste system is required. Planning this early helps you set a realistic budget and avoid mid-project changes.

5. Plan ahead when moving fixtures

Relocating a shower, bath, or toilet almost always means reconfiguring drainage. This may involve cutting into concrete or lifting timber floors, which adds time and cost. Get a clear plan and price from your plumber upfront. All work must meet the New Zealand Building Code, so use a licensed professional to ensure compliance.

Disclaimer: This article is based on a podcast featuring insights from experienced professionals and is intended for general information and inspiration only. While we aim to share valuable guidance, please seek personalised advice from qualified professionals before making decisions about your property, finances, or renovation plans.