Why we don't quote years
Lifespan figures float around online, but we haven't found an official New Zealand source for them, so we don't repeat them. Even the makers don't offer one answer: Rheem says its warranty terms vary by model and are set out in the owner's guide that comes with each new unit.
A warranty is the maker's promise about defects for a set period. It isn't a forecast of how long your cylinder will keep going.
Work out how old yours is
Look for the rating label on the cylinder. When the install date is unknown, Rheem falls back on the date of manufacture and serial number printed there.
For the warranty, though, the install date is what counts. Rheem's residential cover starts on the day of installation for products made after 1 June 2018. Rinnai wants proof of installation, and if that can't be shown for one of its mains pressure cylinders, the cover is counted from the date it was made.
What wears a cylinder out
Hard water. Whanganui District Council, for one, says hardness can cause scale on elements and plumbing fittings. If your supply is hard, ask the plumber what that means for your cylinder's parts.
Leaks. Rheem's owner's guide says even a small leak wastes a surprisingly large amount of hot water and energy. Dripping hot taps and weeping fittings keep the cylinder reheating to cover the loss.
How it was installed. The Building Code expects water systems to be installed to avoid leaks, with reasonable access to parts likely to need maintenance and a way to isolate the system. A cylinder boxed in with no access is harder to look after.
Missing safety parts. Rheem's warranty excludes installations that leave out a properly drained safe tray where its guide calls for one, and its All Pressure guide asks for seismic restraint against earthquake forces. Both are part of a proper install.
Signs worth getting checked
- Water under the cylinder or in its safe tray, or damp around the cupboard.
- Hot water running out sooner, with nobody new in the house.
- Water that's only lukewarm, or swings between hot and cool.
- Brown or rust-coloured water at the hot taps alone.
- A relief valve that runs constantly rather than the odd drip.
- Sounds the cylinder never used to make. See cylinder making noise.
Repair or replace?
Plenty of faults are parts, not the whole cylinder. Rheem names a faulty tempering valve as one cause of water that isn't hot enough, and that's a valve a plumber can test and replace.
Consent follows the same split. Clause 36 of Schedule 1 exempts repairing or maintaining an existing water heater with comparable products, while a replacement has to fit clause 37 or 38. Either way an authorised person does the work, and it must still meet the Building Code.
If there's water about, ask the plumber to show you where it's coming from. A valve or a fitting is a very different job from the cylinder itself.
Look after the one you have
Record the install date
Take it from the invoice, or use the rating label's date of manufacture as a fallback. Keep it with the owner's guide.
Deal with drips promptly
Rheem's advice is to replace faulty tap washers and have your plumber fix any leaking pipework.
Leave the thermostat alone
Rheem says temperature adjustments are for an authorised person, and the system has to stay able to control legionella.
Keep it reachable
Don't shelve or box in around the cylinder. Its valves and parts need to stay within reach for maintenance.
Plan the next one early
Once it's getting on, get quotes before it fails, so you choose the type and the tradie in your own time.
Questions to ask the plumber
- Is this a part that can be replaced, or is the cylinder itself failing?
- Does this cylinder have an anode, and what condition is it in?
- Is our water hard enough to matter for the element or the valves?
- Is there a safe tray and seismic restraint, and are they doing their job?
- If it's replaced, what warranty comes with the new model, and from which date?
What we would do
Get the paperwork into one place now: the invoice with the install date, the owner's guide and any gas certificate. If the cylinder is getting on or showing any of the signs above, ask an authorised tradie who knows hot water cylinders to look over the valves, the tray and the restraints, and to tell you plainly whether it's worth keeping. Replacing on your own timetable beats replacing in a rush.