If you have rung three plumbers about replacing a hot water system, you have probably had three quotes that are hundreds of dollars apart. That is not three different opinions about the tank. It is almost always the valves, and it is worth understanding before you pick the cheapest number.
First: does it actually need replacing?
Most hot water systems in Brisbane are electric storage tanks. They generally last about fifteen years, and then the tank splits and starts leaking water. Once the tank itself is leaking it cannot be repaired — it has to be replaced.
But "no hot water" is not the same as "leaking tank". If the unit is dry underneath and the water has simply gone cold, you are far more likely to be looking at a failed element or thermostat, which is a job of about an hour. We have written that up separately in no hot water? you probably don't need a new system.
Worth checking before you call anyone: is there water pooling under the unit or running down the wall behind it, and is the tank sweating in a way it did not used to? A tank that is genuinely leaking usually leaves a rust stain down the casing.
Why the quotes vary so much
Regulations have changed several times over the years. The result is that replacing a hot water system in 2026 is rarely just swapping the cylinder: it is very likely you need valves that were not fitted when the old one went in.
This is where quotes separate. A quote that only covers the tank and the labour will always look better than one that covers the tank, the labour and the four valves the installation now needs. It is the same job on paper and a different job in the roof space.
If those valves are left out, you void the 7–12 year warranty on your new system. So the cheap quote is not a saving — it is the warranty, removed, in exchange for a few hundred dollars.
The valves, and what each one actually does
Every hot water system comes with a pressure temperature relief valve. That one is in the box. These are the ones that get left off a thin quote:
- Duo valve — the on/off tap on the cold water supply. It is also what a plumber uses to isolate the unit, which is why you want to know where it is before you have an emergency.
- Pressure limiting valve — limits the cold water supply pressure to 500 kPa. Mains pressure in parts of Brisbane runs well above that, and a tank fed at full mains pressure does not last as long as it should.
- Cold water expansion valve — relieves pressure from the tank as the water in it heats up and expands. Without somewhere for that pressure to go, it goes into the tank wall.
- Tempering valve — limits the hot water temperature at the tap to a maximum of 50 °C. This is the scald-protection one, and it is the one worth being pleased about if you have small children in the house.
Can the old valves be re-used?
Sometimes, and we will tell you which when we look at it. We can generally re-use valves across most hot water system brands. But if the existing valves are more than fifteen years old we recommend replacing them, because a fifteen-year-old valve on a brand-new tank is the next call-out you are going to make.
What it costs installed
These are supply-and-install prices for Rinnai and Rheem electric storage systems. Each range spans both brands — which one suits depends on the space and the connections already in place.
| System | Fully installed | |---|---| | 25 L | $825 – $1,075 | | 50 L | $859 – $1,109 | | 80 L | $969 – $1,219 | | 125 L | $1,029 – $1,279 | | 160 L | $1,189 – $1,439 | | 250 L | $1,299 – $1,549 | | 315 L | $1,399 – $1,649 | | 400 L | $1,599 – $1,849 |
All prices are GST inclusive and subject to site inspection.
Which size do you need?
The honest answer is: the same size you had, unless something about the household has changed. People tend to go up a size after a bad week of cold showers and then pay to heat water they never use.
As a rule of thumb, a 125–160 L electric tank suits a couple or a small family, 250 L suits four people with a decent-sized bathroom, and 315 L and up is for larger households or houses with two bathrooms in use at the same time. If everybody showers in the same hour of the morning, size up. If the showers are spread across the day, you do not need to.
Four questions worth asking any quote
- Does this include the valves? Name them. Duo, pressure limiting, cold water expansion, tempering.
- Is it GST inclusive? A number that turns out to be plus GST is 10% worse than the one you compared it against.
- What happens to the old unit? It has to go somewhere, and removal and disposal is part of the job.
- Who honours the warranty? The manufacturer warrants the tank; the installation has to be compliant for that warranty to stand.
What we do
We install any brand of hot water system at reasonable prices, and our plumbers will have you up and running as fast as we can. We will tell you whether the existing valves can stay, and the quote will say what it includes.
See the full detail on hot water systems, or call us and describe what the unit is doing. If it is leaking now, that is an emergency — turn the cold water supply off at the duo valve on the side of the unit, switch off its power, and call.
More on Hot water systems, including what we charge.