Only cold water in the shower? A puddle under the cylinder? Strange noises from the cupboard? Here’s how to tell what’s wrong with your hot water cylinder, what you can safely check yourself, and when it’s time to call a plumber.
Most homes in New Zealand heat their water with a hot water cylinder, and most cylinders run for years without a problem. When one does play up, it’s usually one of the problems below.
Water leaking or no hot water right now? See emergency hot water. We’re on call 24/7.
No hot water? Check these first
A few quick checks can save you a call-out:
- Is there cold water? If no water comes out of any tap, the problem is your water supply, not the cylinder. On tank or bore water, check the pump: see what to do when your water pump stops working.
- Check the switchboard. Make sure the hot water switch is on and the circuit breaker hasn’t tripped. If it trips again when you switch it back on, leave it off and call us. That points to an electrical fault, often the element.
- Heat pump or a controller? Look for an error code on the display and check it in the manual. Tell us the code when you call, as it helps us bring the right parts.
- Used a lot of hot water? After several showers or a bath, the cylinder needs time to heat up again.
If all of that looks fine, the cause is usually inside the cylinder: a failed element, a faulty thermostat, or a tempering valve that has stopped letting hot water through. These parts run on 230 volts or sit under mains pressure, so leave the covers on. We find the faulty part and replace it, often without needing a new cylinder. See hot water cylinder repairs.
Help, my hot water cylinder is leaking!
Act straight away, even if it’s only a small drip. A leak usually gets worse, and the water can damage floors and walls.
What to do now:
- Turn off the power to the cylinder at the switchboard (the switch marked hot water or cylinder).
- Turn off the cold water to the cylinder at the valve on the cold pipe going into it. If you can’t find it, turn off the water at the main tap, or on tank water switch off the pump.
- Keep clear of the hot water and soak up what you can.
- Call us. We’re on call 24/7 for leaking cylinders.
Where is it leaking from?
- The tank itself (from the base, a seam or a rusty patch). The inside of the cylinder has corroded through. This can’t be repaired, so the cylinder needs replacing: see hot water cylinder replacement.
- A valve, fitting or pipe joint. Usually repairable. We replace the faulty valve or remake the joint.
- Around the element (behind the lower cover). Often a worn element seal, which can be replaced.
- From the drain pipe outside. That’s a relief or expansion valve letting water out. See the next section.
From our years of hot water work around Rodney, a leak from the tank of an older cylinder is usually a sign of age. If the tank is sound, a repair is often all it needs, and we’ll tell you honestly which it is.
An old mains pressure cylinder leaking from the base.
A new cylinder we fitted on a drip tray, so a small leak drains away instead of spreading across the floor.
Water dripping from the overflow pipe?
Mains pressure cylinders have valves that let water out through a drain pipe, often outside near the cylinder, to keep the pressure safe.
- A small drip while the cylinder is heating is usually normal. Water expands as it heats, and the expansion valve lets the extra out.
- A steady flow, or dripping all day, means a valve isn’t doing its job. Often the pressure limiting valve or the expansion valve needs replacing. It wastes water and, on tank water, keeps your pump running.
- Hot water or steam from the drain pipe, or from the vent pipe on the roof of an older low pressure cylinder, can mean the cylinder is overheating. Turn off the power to the cylinder and call us straight away.
Don’t block or cap a drain pipe to stop the drip. The valves are there for safety.
Hot water cylinder is making noise
- Is your hot water cylinder making a banging noise?
- Is your hot water cylinder making a whistling noise?
- Hearing a buzzing noise from your hot water cylinder?
- Is there a loud noise coming from your hot water cylinder?
As soon as your hot water cylinder draws attention with unusual noises, you need to get to the bottom of the problem. But what are strange noises from a hot water cylinder? Some noise is normal while the water heats, and a heat pump water heater hums when its fan and compressor run. However, if you regularly hear unusual popping, gurgling or rattling noises, it indicates a potential defect.
If the heating element is deteriorating, your hot water cylinder may pop, crack, or even whine. Burnt sediment and limescale can cause the same sounds, and scale builds up faster where the water is hard, as some bore water is. In both cases, we highly recommend giving us a call. Our plumbers will come on-site and investigate why your hot water cylinder is making loud noises.
Be careful if the hot water cylinder makes a gurgling or even boiling sound! This is likely a pressure rise or severe overheating in the water tank. Turn off the power to the cylinder and call our 24/7 line on 021 278 7427.
Banging in the pipes when a tap is turned off quickly is usually water hammer in the pipework, not the cylinder. We can fix that too.
Why does my hot water suddenly smell like rotten eggs?
First, run a cold tap. If the cold water smells and looks fine, the problem is in the hot water cylinder. If the cold water smells too, the problem is your water supply: see what can be in your drinking water, or ask us about a water test.
A rotten-egg smell from the hot water only is usually caused by bacteria in the cylinder reacting with the anode, a metal rod in many mains pressure cylinders that protects the tank from corrosion. Brown or rusty hot water can mean the anode is worn out and the tank has started to rust.
A smell can usually be fixed by replacing the anode and flushing the cylinder, without a new cylinder. Rusty water from an older cylinder is often a sign the tank is near the end of its life: see signs your hot water cylinder needs replacing.
Running out of hot water, or low pressure?
- The cylinder is too small for the household now, for example after the family has grown.
- The element or thermostat is failing, so the water heats slowly or doesn’t get hot enough.
- Sediment or scale has built up in the bottom of the cylinder. On tank water with no filtration, it can be a lot: see what 12 years of unfiltered tank water does to a cylinder.
- A faulty tempering valve can make the water lukewarm at the bathroom taps.
- An old low pressure cylinder. Many older homes still have one, and the flow is weak, especially upstairs or with two showers running. Upgrading to a mains pressure cylinder gives strong, even pressure. On tank water, a mains pressure cylinder needs a pump that can keep up: see water pumps.
We’ll find what’s causing it and talk you through the options, including replacing or upgrading your cylinder or a heat pump water heater.
When to call a plumber straight away
- Water leaking from the cylinder itself
- Steam, or hot water running from a drain or vent pipe
- Gurgling or boiling sounds
- The hot water circuit breaker keeps tripping
- Water much hotter than usual, or a burning smell near the cylinder
- Rusty or brown hot water
Please don’t try to repair the element, thermostat or valves yourself. It’s work for a licensed plumber and electrician, and the cylinder holds hot water under pressure.
Repair or replace?
Most faults, like an element, thermostat or valve, can be repaired. A leaking tank, a lot of rust, or an old cylinder with repeated faults usually means it’s time for a new one. We’ll check it on site and give you honest advice for your home and budget. Read more about the signs your hot water cylinder needs replacing.
A regular service helps a cylinder last longer. We check the valves, element and thermostat, look for leaks or corrosion, and make sure the water is heating properly. See hot water cylinder repairs and servicing.
From Mangawhai to Albany, our team repairs and replaces hot water cylinders across Rodney, the Hibiscus Coast and North Auckland. See all our hot water services.
Hot water cylinder brands we repair
We repair and service all the common brands, including Rheem, Stanley, Simplex, Rinnai, Bosch, Thermann and Dux, and copper low pressure, enamel, stainless steel and heat pump cylinders. If your brand isn’t listed, give us a call.
Local to Rodney?
We repair, service and replace hot water cylinders right across Rodney and North Auckland, from Mangawhai to Albany. Tell us what your cylinder is doing and we’ll get it sorted. For a leak or no hot water after hours, see emergency hot water.
Hot water cylinder problems: FAQs
Is it normal for a hot water cylinder to make noise?
Some noise is normal while the water heats, and a heat pump water heater hums when it runs. Regular popping, crackling or whining usually means scale build-up or a failing element. Gurgling or boiling sounds can mean the cylinder is overheating: turn off the power to the cylinder and call us.
Why is my hot water cylinder leaking from the bottom?
Usually because the tank has corroded through, which means the cylinder needs replacing. A leak can also come from the element seal or a valve or fitting near the bottom, which can often be repaired. Turn off the power and the cold water to the cylinder, then call us.
Is it normal for the hot water cylinder overflow pipe to drip?
A small drip while a mains pressure cylinder is heating is usually normal. A steady flow, dripping all day, or hot water or steam coming out is not. Call us to check the valves.
Why have I suddenly got no hot water?
Check the hot water switch and circuit breaker at the switchboard, and whether the cold water is working. If the breaker trips again, or everything looks fine, the element or thermostat has usually failed. We can test and replace them.
Can I fix my hot water cylinder myself?
You can safely check the switchboard, look for leaks and read any error code. Repairs to the element, thermostat and valves need a licensed plumber and electrician, because the cylinder holds hot water under pressure and runs on 230 volts.
Do you come out after hours for hot water cylinder problems?
Yes. For a leaking cylinder or no hot water, call our 24/7 line on 021 278 7427. We cover Rodney and North Auckland, from Mangawhai to Albany.