Thermann gives a general replacement guide of around 7–10 years, while noting that some systems last longer. That is a planning guide, rather than an expiry date. System type, water conditions, use and maintenance matter, so assess its condition and repair history before deciding to replace it.
Manufacturer reference: Thermann’s hot-water FAQs.
What affects how long a system performs?
Different system types have different components and operating conditions. Water quality, demand, installation and maintenance can also affect wear. Check the manufacturer’s information for the specific model rather than relying on a general age rule.
Which signs deserve attention?
No hot water, recurring faults, inconsistent temperature, visible corrosion or water leaking from the unit can warrant an assessment. A small amount of discharge from a relief outlet can occur during normal operation, so do not block it; if you are unsure whether a leak is normal, have it checked.
How to plan the next step
If you know it, note the system type, model and approximate installation date. Describe the symptoms and any previous repairs. A plumber can assess its condition and explain whether a repair or replacement is appropriate for the fault.
When should you call a plumber?
- Water is leaking from the tank, unit or pipe connections.
- The system has stopped, repeatedly faults or no longer meets household needs.
- You see corrosion or notice a significant change in hot-water performance.
- You need an assessment before budgeting for a replacement.
What affects the cost?
An assessment or repair depends on the fault, parts and access. Replacement depends on the type and capacity selected, removal, installation access, and any changes to plumbing, gas or electrical connections. A model-specific quote is more useful than estimating from age alone.