Replace your hot water cylinder in NZ when it's 10–15 years old, showing rust, leaking from the tank body, or requiring frequent repairs. Most NZ cylinders last 12–15 years. Replacing before failure avoids emergency costs and water damage risk.
Low-pressure copper cylinders: 15–25 years. Mains pressure cylinders: 10–15 years. Heat pump units: 15–20 years. Christchurch's post-earthquake ground movement can stress pipe connections and shorten effective cylinder life in some properties.
A cylinder failing suddenly can release 180–360 litres of near-boiling water — causing serious water damage. Emergency replacement carries after-hours premium costs. Proactive replacement on your schedule is almost always cheaper and less stressful.