Make it safe first
If water is pooling under the cylinder or coming through a ceiling, switch the cylinder off at the switchboard and close the valve on the cold pipe feeding it, or the toby (the water shut-off at your boundary) if you can't find one. If you smell gas, don't relight anything or use switches nearby; get everyone outside and ring your gas supplier's emergency number from there, and see gas leaks. Never take covers off a cylinder or heater: Rheem says repairs that need covers removed with tools are for a qualified plumber, gasfitter or electrician.
Which kind do you have?
The checks depend on how your water is heated. The rating label on the side names the maker and model, so take a photo of it now; the tradie will ask.
An electric cylinder heats stored water with an element. A gas storage heater does the same with a burner. Gas continuous flow, often called a califont, has no tank and heats water as it passes through. A heat pump water heater draws warmth from the air into its tank and has an electric back-up element. Solar has a gas or electric boost, and a wetback heats the cylinder from your wood or pellet fire.
Checks you can do safely
Run every hot tap
If the kitchen runs hot but the bathroom doesn't, the cylinder may be fine. Bathroom water may pass through a tempering valve, and Rheem notes a faulty one can cool hot water too much.
Check the switchboard
Look for a tripped switch or fuse marked hot water or cylinder, and reset it once. If it trips again, leave it off: that points to an electrical fault, which is for an electrician or your hot water tradie.
Check the gas
Try the hob or another gas appliance. If nothing gas works, the supply is the problem, so check the valve at the meter is open or whether the LPG bottles have run out.
Think about the heat source
A wetback only heats while the fire is going, and the rest of the time the element does the work. Solar leans on its boost on dull days, and a heat pump on its back-up element when it's very cold. If one of those is switched off, expect less hot water.
Write down any code
If the unit or its controller shows a code or a warning light, note it exactly. It tells the tradie where to start.
Stop and ring for help if
- Water is pooling under the cylinder, or the safe tray has water in it.
- The switch trips again after one reset.
- You smell gas, or a gas heater won't stay lit.
- You see steam, or hear boiling or banging from the cylinder.
- The relief valve runs all the time, not just the odd drip.
- Hot water comes out rusty, smelly or gritty.
Who does what
A hot water job can need up to three trades. The plumbing must be done by someone authorised under the Plumbers, Gasfitters, and Drainlayers Act 2006. On a gas heater, an authorised gasfitter does the gas side, and a gasfitter the Board accepts as competent can also fit the heater's water pipes. An electrician makes the electrical connection.
Check the person, not the business name. Search their first and last name on the PGDB public register and look for a current licence; being listed isn't enough, because former licence holders are on it too. Our guide to checking a PGDB licence shows how.
Repair or replace?
Ask about repair first. Elements, thermostats and valves are parts, and repairing or maintaining an existing water heater with comparable products is exempt from building consent. A replacement is exempt only in the conditions set out in Schedule 1 of the Building Act, which our building consent guide explains.
Whichever way it goes, an authorised person has to do the work, and the result must meet the Building Code.
Have this ready when you ring
- The type of heater, and the maker and model from the rating label.
- Roughly how old it is, or the install date from the invoice.
- What you've checked, and what happened.
- Any code or warning light, written down.
- Photos of the label, the valves and any water.
Questions to ask the tradie
- Is it a part, and do you have the part?
- Is the cylinder itself still sound?
- If it has to be replaced, which consent exemption covers it, if any?
- Who will do the gas or electrical side?
- What paperwork will I get, such as a gas certificate?
What we would do
One pass through the checks is enough. If the hot water isn't back after that, more fiddling won't help and can make a fault harder to trace. Book an authorised tradie who specialises in hot water cylinders, give them the label photo and what you found, and ask them to price the repair before anyone talks about a new cylinder.