Signs your cylinder needs a look
- Water pooling under or around it.
- No hot water, or it runs out much sooner than it used to.
- Only ever lukewarm, even with the power on.
- Brown or smelly water from the hot taps but not the cold.
- The switchboard trips when it starts heating.
Low pressure or mains pressure?
Low pressure copper electric cylinders are made to NZS 4602 for working pressures of no more than 120 kPa. They can be open vented, with a vent pipe, or valve vented, with a pressure relief valve instead, so low pressure doesn't always mean open vented. Above 120 kPa, a different standard (NZS 4606) applies.
A mains pressure cylinder takes water at street pressure, so hot and cold run at the same pressure. Whether a low pressure home can change over is the plumber's call after a look at the pipes: see our conversion guide.
Ways to heat the water
| How it works | Worth knowing | |
|---|---|---|
| Electric cylinder | An element heats stored water | Comes in low and mains pressure versions |
| Gas storage | A gas burner heats a stored tank | The gas side needs an authorised gasfitter |
| Gas continuous flow (often called a califont) | Heats water only while a hot tap runs | Rheem says it needs a larger gas pipe from the meter than most storage heaters |
| Heat pump water heater | Draws warmth from the air into a tank | Needs outdoor space, which can mean moving the cylinder |
| Solar | Roof collectors, with a gas or electric boost | Collectors do best facing north, out of shade |
| Wetback | Pipework in a wood or pellet fire heats water for the cylinder | Where the fire sits decides whether it works |
Brand notes are Rheem's descriptions of its own products; we aren't tied to any brand. Compare heat pump hot water and califonts.
What a plumber will do
Make it safe
A plumber will isolate the water and have the power or gas turned off first.
Find the fault
They'll tell you whether it's a part, such as a valve, or the cylinder itself.
Lay out the options
Repair, a like-for-like replacement, or a different kind of heater.
What changes the size of the job
- Where it sits: a cupboard, the ceiling space or outside. Moving it is bigger than swapping in place.
- Changing pressure, or changing fuel. Gas brings in an authorised gasfitter.
- Changing kind: a heat pump water heater needs outdoor space and an electrician.
- A wetback connection, and the state of the pipes the new cylinder joins.
When replacing a cylinder is exempt from building consent
Building work needs a building consent unless the Building Act exempts it. Schedule 1 exempts three kinds of water heater work, and only when a person authorised under the Plumbers, Gasfitters, and Drainlayers Act 2006 does it:
- Repair or maintenance of an existing water heater using comparable products (clause 36).
- Replacing a water heater, or repositioning one, if the replacement is connected to, or includes, a controlled heat source, or, with more than one heat source, all of them are controlled (clause 38).
- Replacing a cylinder on a wetback or other solid-fuel heater, only with a comparable open-vented cylinder fixed in the same position on the same pipework (clause 37).
The general plumbing repair exemption doesn't cover water heaters, and exempt work must still meet the Building Code. A homeowner using the householder exemption doesn't count as authorised. The Act's text doesn't define 'controlled heat source', so ask the plumber which clause applies before work starts. Our consent guide goes clause by clause.
Who is allowed to do the work
Whoever works on your cylinder must be authorised under the Plumbers, Gasfitters, and Drainlayers Act, usually through a current practising licence from the Board (PGDB); registration alone isn't enough. Licences expire on 31 March each year. Only certifying plumbers work unsupervised and can certify work; everyone else works under a named certifying supervisor.
On gas, a licensed gasfitter the Board accepts as competent may fit the heater and its water pipes. You need a Gas Safety Certificate once it's connected, plus a certificate of compliance for general or high-risk gasfitting (optional for a low-risk like-for-like swap).
Unauthorised plumbing carries fines of up to $10,000, and knowingly paying an unauthorised person is an offence too. PGDB warns unlicensed work may void your insurance. Here's how to check a licence.
What you can do, and what to leave
You can
- Check its switch and breaker at the switchboard.
- Photograph the label: brand, model, capacity and pressure.
- If it's leaking, turn off its power or gas, and the cold water feeding it if that's safe.
Leave to an authorised tradie
- Fixing or unfixing pipes, or the cylinder and its valves. PGDB lists pipes, fixtures and appliances among what homeowners can't fix or unfix.
- Thermostat settings: Rheem says an authorised person adjusts them.
- Gas connections and flues (a gasfitter) and wiring (an electrician).
Questions to ask before you agree
- Is it a part, or is the cylinder finished?
- What name will I find for you on the PGDB register, and who supervises you?
- Which Schedule 1 clause makes this consent-exempt?
- Is this a quote or an estimate?
- What documents will I receive when the work is completed?
What we would do
If the body of the cylinder is leaking, stop spending on it and plan the replacement; if it's a part, fix the part. Check the name of whoever does the work on the PGDB register, and ask which consent exemption applies. Thinking of a heat pump, gas or mains pressure? Decide before the old one dies, so a hot water specialist can check your pipes, space and supply first.