Rheem Instant Hot Water Systems Review: Are Rheem Continuous Flow Gas Units Worth It?

Rheem instant hot water systems are a popular option for Australian homes that want continuous flow gas hot water without a large storage tank. Instead of storing hot water, an instant gas unit heats water as it passes through the system, which can suit households wanting compact outdoor installation, strong flow options and hot water on demand.

But a Rheem instant gas hot water system is not the right choice for every home. It depends on your gas type, gas pipe sizing, water pressure, number of bathrooms, household demand, installation location, electrical supply, outdoor clearances and whether you are ordering supply only or choosing a supplied-and-installed option where available.

This Rheem instant hot water systems review explains where Rheem continuous flow gas hot water can make sense, what to check before ordering, and when it may be worth comparing alternatives from Rinnai, Bosch, Dux, heat pump hot water or other gas hot water options.

You can compare Rheem hot water systems, instant gas hot water systems, gas hot water systems and all hot water systems online with Installed Today.

Quick answer: are Rheem instant gas hot water systems worth considering?

A Rheem instant gas hot water system can be worth considering if your home already has natural gas or LPG, the gas supply is suitable, and you want a compact continuous flow unit rather than a storage tank.

Rheem instant gas may suit:

• Homes already connected to natural gas

• Homes using LPG where the correct LPG model is selected

• Properties replacing an existing continuous flow gas unit

• Homes wanting a compact wall-mounted unit

• Households with moderate to high hot water demand

• Two-bathroom homes where the correct flow rate is selected

• Customers wanting gas hot water without a large storage tank

• Supply-only customers with their own licensed gas fitter arranged

• Eligible Brisbane and Gold Coast customers where supplied-and-installed options are available

It may not suit homes without gas, homes with undersized gas pipework, properties with poor water pressure, or customers wanting the lowest possible running cost from a solar-supported electric setup.

What is a Rheem instant hot water system?

A Rheem instant hot water system, also called a continuous flow gas hot water system, heats water only when a hot tap is opened.

Unlike a storage tank, it does not keep a large volume of water hot all day. Water passes through the unit and is heated by a gas burner as needed.

Rheem instant gas systems may be available in different flow rates, commonly compared around sizes such as:

• 16 L/min

• 20 L/min

• 26 L/min

The right size depends on household demand, number of bathrooms, incoming water temperature, gas supply, water pressure and whether multiple outlets may run at the same time.

Rheem instant gas hot water pros

Rheem continuous flow gas systems can offer several practical benefits when correctly selected.

Potential advantages include:

• Compact wall-mounted design

• No large storage tank

• Hot water heated on demand

• Suitable for many homes already using gas

• Common flow rate options for different household sizes

• Natural gas and LPG options depending on model

• Can suit family homes where correctly sized

• Can suit replacement of an older instant gas unit

• Outdoor installation options depending on model

• Supply-only ordering available where you have your own licensed gas fitter arranged

• Supplied-and-installed options may be available on selected products in eligible Brisbane and Gold Coast areas

For homes already set up for gas, Rheem instant hot water can be a practical category to compare.

Rheem instant gas hot water cons

Rheem instant gas is not always the best option.

Potential drawbacks include:

• Requires suitable natural gas or LPG supply

• Gas pipe sizing must be checked

• Water pressure must be suitable

• Installation must be completed by a licensed gas fitter

• Many units require power for ignition and controls

• Outdoor clearances must comply with requirements

• Temperature controllers may add cost where used

• Simultaneous outlet performance depends on sizing

• Delayed hot water can still occur due to pipe run length

• Not ideal for homes wanting to avoid gas

• Not usually suitable for indoor installation unless using a manufacturer-approved internal/flued model

The biggest mistake is choosing a 26L-style unit without confirming gas pipe sizing, water pressure and installation location first.

Rheem 16L vs 20L vs 26L instant gas

Flow rate is one of the most important choices.

A larger flow rate is not automatically better. A 26L unit still needs suitable gas supply, water pressure and pipework to perform properly.

Rheem 26L instant gas hot water review

A Rheem 26L instant gas hot water system is commonly compared for family homes and two-bathroom properties.

It may suit:

• Medium to large homes

• Two-bathroom households

• Families with higher hot water demand

• Homes replacing an existing 26L continuous flow unit

• Properties with suitable gas pipe sizing

• Homes with suitable water pressure

• Outdoor wall-mounted installation locations

Before ordering a Rheem 26L instant gas system, check:

• Natural gas or LPG model

• Gas pipe sizing

• Water pressure

• Existing unit size

• Number of bathrooms

• Shower flow rates

• Pipe run length

• Outdoor clearances

• Electrical connection

• Temperature controller requirements

• Licensed gas fitter confirmation

A 26L system can be a strong choice, but only when the home’s gas and water supply can support it.

Natural gas vs LPG Rheem instant hot water

Natural gas and LPG are not interchangeable.

Before ordering any Rheem gas hot water system, confirm:

• Whether the property uses natural gas or LPG

• Whether the existing unit label shows gas type

• Whether there is a natural gas meter

• Whether the property uses LPG bottles

• Whether the new model matches the gas type

• Whether your licensed gas fitter has confirmed suitability

Ordering the wrong gas type can delay installation and create extra cost.

Rheem instant gas for small homes

A Rheem instant gas system may suit a small home if the property already has gas and the selected flow rate matches demand.

Small homes may suit instant gas where:

• There is one bathroom

• Gas supply is already available

• Outdoor wall space is suitable

• The system is replacing an existing instant gas unit

• Hot water demand is moderate

• The household wants a compact unit

A smaller flow rate may be enough for some one-bathroom homes, but shower habits and incoming water temperature still matter.

Rheem instant gas for family homes

Family homes need more careful sizing.

Check:

• Number of bathrooms

• Number of people

• Shower habits

• Back-to-back showering

• Bath use

• Morning and evening peak demand

• Whether multiple outlets run at once

• Gas pipe sizing

• Water pressure

• Existing pipe run length

A family home may need a larger flow rate, but performance depends on the whole installation setup, not just the unit rating.

Rheem instant gas for two-bathroom homes

A two-bathroom home is one of the most common reasons customers compare larger instant gas units.

Before choosing a Rheem instant gas system for a two-bathroom property, check:

• Whether both showers may run at the same time

• Shower rose flow rates

• Gas pipe capacity

• Water pressure

• Distance from unit to bathrooms

• Temperature controller needs

• Whether the old system struggled

• Whether 20L or 26L is more suitable

If two showers are likely to run together, a licensed gas fitter should confirm that the selected unit and gas supply can handle the load.

Rheem instant gas for rental properties

Rheem instant gas can suit rental properties where the home already has gas and the unit is correctly sized.

For rentals, consider:

• Number of bedrooms

• Number of bathrooms

• Likely tenant demand

• Simple operation

• Gas type

• Warranty documentation

• Maintenance access

• Replacement cost

• Installer availability

• Outdoor unit location

A rental property should be sized for likely tenant use, not only the current tenant.

Rheem instant gas for Airbnb and short-stay homes

Short-stay properties need reliable hot water for maximum guest occupancy.

A Rheem instant gas system may suit some Airbnb homes if the gas supply and flow rate match peak demand.

Check:

• Maximum guest count

• Number of bathrooms

• Back-to-back showers

• Laundry between stays

• Bath use

• Gas supply

• Water pressure

• Temperature controller setup

• Guest simplicity

• Maintenance access

For short-stay properties, guest comfort matters more than choosing the smallest or cheapest system.

Rheem instant gas for renovations

A renovation is a good time to plan hot water properly.

Before choosing Rheem instant gas for a renovation, confirm:

• Final bathroom count

• Fixture locations

• Gas supply location

• Gas pipe sizing

• Water pressure

• External wall location

• Drainage and discharge requirements

• Electrical connection

• Temperature controller wiring if used

• Access after the renovation is finished

• Whether gas or heat pump is the better long-term fit

Do not leave hot water selection until after the bathroom and kitchen layout is locked in. Pipe runs and gas sizing can affect performance.

Rheem instant gas vs gas storage

Rheem instant gas and gas storage systems are different.

Instant gas can be a good choice where space is limited and gas supply suits. Gas storage may suit homes wanting stored hot water and strong recovery where the location suits.

Rheem instant gas vs electric storage

Electric storage and instant gas suit different properties.

Rheem instant gas may suit:

• Homes with gas

• Outdoor wall-mounted locations

• Customers wanting continuous flow

• Homes replacing old instant gas units

• Properties wanting no large tank

Electric storage may suit:

• Homes without gas

• Units and townhouses

• Simple like-for-like electric replacement

• Lower upfront installation complexity in some homes

• Off-peak electricity setups where suitable

If the home does not already have gas, changing to instant gas may involve extra cost and may not be worthwhile.

Rheem instant gas vs heat pump hot water

A Rheem instant gas system and a heat pump hot water system are very different choices.

Instant gas uses natural gas or LPG. A heat pump uses electricity to draw heat from the surrounding air and heat stored water.

Heat pump hot water may suit:

• Homes replacing electric storage

• Homes with rooftop solar

• Customers wanting an efficient electric option

• Properties with suitable outdoor space

• Homes with good airflow and drainage

Instant gas may suit:

• Homes already connected to gas

• Customers wanting compact continuous flow hot water

• Homes with suitable gas pipe sizing

• Properties replacing existing instant gas systems

If you are comparing long-term running costs, also compare heat pump hot water systems.

Rheem vs Rinnai instant gas

Rheem and Rinnai are both common choices for instant gas hot water.

When comparing Rheem hot water systems with Rinnai hot water systems, check:

• Flow rate

• Natural gas or LPG model

• Minimum flow requirements

• Temperature controller options

• Warranty terms

• Dimensions

• Outdoor clearances

• Gas connection requirements

• Water pressure requirements

• Installer familiarity

• Product availability

• Total replacement cost

Do not choose by brand alone. Compare the exact model against the property.

Rheem vs Bosch instant gas

Rheem and Bosch may both be compared by customers considering gas continuous flow hot water.

When comparing Rheem with Bosch hot water systems, check:

• Ignition method

• Natural gas or LPG compatibility

• Flow rate

• Minimum operating flow

• Water pressure requirements

• Outdoor clearances

• Warranty terms

• Service requirements

• Installation cost

• Whether power is required for the selected model

The best choice depends on the existing services and how the home uses hot water.

Rheem vs Dux gas hot water

Rheem and Dux may be compared by customers wanting gas hot water or broader hot water replacement options.

When comparing Rheem with Dux hot water systems, check:

• Instant gas vs storage preference

• Flow rate or tank size

• Gas type

• Warranty terms

• Installation location

• Gas pipe sizing

• Water pressure

• Product availability

• Total cost

The right choice is the system that suits the home and installation setup.

Installation requirements for Rheem instant gas

Rheem instant gas hot water systems need professional installation.

Installation checks may include:

• Natural gas or LPG supply

• Gas pipe sizing

• Water pressure

• Existing hot water system type

• Existing unit location

• Outdoor clearances

• Flue or ventilation requirements where relevant

• Electrical connection

• Temperature controller wiring

• Pipework changes

• Valves

• Drainage and discharge

• Compliance requirements

• Old unit removal

• Disposal

A licensed gas fitter should confirm product suitability before installation.

Outdoor installation and clearances

Most residential external instant gas hot water units are designed for outdoor installation. Internal installation should only be considered where the model is specifically designed and approved for internal or flued installation.

Outdoor installation requires attention to clearances around:

• Windows

• Doors

• Eaves

• Vents

• Boundaries

• Gas meters

• Air intakes

• Electrical equipment

• Walkways

• Outdoor living areas

Clearance requirements matter for safety and compliance.

Does Rheem instant gas need electricity?

Many continuous flow gas hot water systems require electricity for ignition, controls and safety features.

Before ordering, check:

• Whether a power point is needed

• Whether the existing unit already has power

• Whether electrical work is required

• Whether the power point location is suitable

• Whether the unit will operate during a power outage

If you specifically need a no-power gas hot water option, compare models carefully and confirm with your licensed installer.

Why hot water can be delayed with instant gas

Instant gas heats water on demand, but it does not mean hot water appears instantly at every tap.

Delay can be caused by:

• Distance from unit to outlet

• Pipe length

• Pipe size

• Existing plumbing layout

• Flow rate

• Water already sitting cold in the pipe

• Fixture type

• Temperature settings

A new continuous flow unit may still have waiting time if the pipe run to the bathroom is long.

Temperature fluctuation: what can cause it?

Temperature fluctuation can be caused by more than the unit itself.

Possible causes include:

• Low flow at fixtures

• Multiple outlets running

• Undersized unit

• Gas pressure issue

• Water pressure issue

• Incorrect gas type

• Blocked filters

• Scale build-up

• Poor installation

• Temperature controller settings

• Cross-connection or tempering valve issue

A licensed professional should diagnose ongoing temperature problems.

Maintenance and servicing

Instant gas hot water systems need periodic servicing to keep them working properly.

Maintenance may include:

• Burner checks

• Heat exchanger inspection

• Water filter cleaning

• Gas pressure checks

• Flue and ventilation checks

• Error code diagnosis

• Scale checks

• Water pressure checks

• Controller checks

• General safety inspection

Homes with hard water, high usage or poor water quality may need more frequent attention.

How long does a Rheem instant gas hot water system last?

System life depends on:

• Installation quality

• Water quality

• Gas supply

• Usage level

• Maintenance

• Location

• Ventilation

• Scale build-up

• Weather exposure

• Product model

• Warranty terms

A well-selected and maintained system can provide long service, but no unit is immune to component wear, scale, installation issues or site-related problems.

Warranty considerations

Before ordering a Rheem instant gas system, check the warranty terms carefully.

Review:

• Heat exchanger warranty

• Parts warranty

• Labour coverage

• Installation requirements

• Maintenance requirements

• Water quality exclusions

• Licensed gas fitter requirements

• Proof of purchase

• Service process

• Natural gas vs LPG model requirements

• What is and is not covered

Warranty coverage does not mean every issue is automatically covered. Incorrect installation, water quality, gas supply issues or lack of documentation can affect claims.

Cost considerations

The total cost of a Rheem instant gas hot water system is not only the product price.

Final cost may be affected by:

• Natural gas or LPG model

• Flow rate

• Installation location

• Gas pipe upgrades

• Electrical power point

• Temperature controllers

• Valve requirements

• Pipework changes

• Access

• Old unit removal

• Disposal

• Compliance upgrades

• Supply-only vs supplied-and-installed options

A like-for-like replacement of an existing instant gas unit is usually simpler than changing from electric storage to gas continuous flow.

Supply-only Rheem instant gas systems

Supply-only ordering can suit customers who already have their own licensed gas fitter arranged.

Supply only may suit:

• Builders

• Renovators

• Landlords

• Property managers

• Trade customers

• Customers managing their own installation

• Customers outside installed service areas

Supply-only product pricing generally does not include installation, gas work, electrical work, valves, pipework changes, old unit removal, disposal, drainage, access upgrades or compliance upgrades unless clearly selected or included.

Before ordering supply only, your licensed gas fitter should confirm that the Rheem system suits the property.

Supplied-and-installed Rheem instant gas systems

Supplied-and-installed options may be available on selected products in eligible Brisbane and Gold Coast service areas where shown.

This can suit customers who want the product and installation pathway arranged together.

Before ordering supplied and installed, check:

• Service area eligibility

• Existing system type

• Natural gas or LPG

• Installation inclusions

• Gas pipe sizing

• Water pressure

• Electrical requirements

• Old unit removal

• Disposal

• Pipework changes

• Access

• Temperature controller options

• Compliance upgrades

Do not assume every possible site requirement is included. Check the product page and selected options carefully.

Common mistake: choosing the wrong gas type

Natural gas and LPG are different.

Do not order based on guesswork. Confirm the existing gas type before choosing a Rheem gas system.

Common mistake: assuming 26L solves every problem

A larger flow rate only helps if the gas supply, water pressure and installation setup can support it.

A 26L unit on undersized gas pipework may not perform as expected.

Common mistake: ignoring water pressure

Instant gas systems need suitable water flow and pressure.

Poor water pressure can affect ignition, flow and temperature stability.

Common mistake: expecting instant hot water at the tap

Instant gas heats water as it flows through the unit, but hot water still needs to travel through pipework to the outlet.

Long pipe runs can still mean a delay.

Common mistake: comparing only energy ratings

Energy efficiency matters, but you also need to compare:

• Gas type

• Flow rate

• Warranty

• Installation cost

• Gas pipe sizing

• Water pressure

• Household demand

• Maintenance

• Total replacement cost

A high-efficiency unit can still be the wrong fit if the home is not suitable.

Common mistake: DIY gas hot water installation

Gas hot water installation must be handled by a licensed gas fitter.

DIY gas installation can create:

• Gas leaks

• Carbon monoxide risk

• Fire risk

• Water leaks

• Warranty problems

• Insurance issues

• Non-compliant work

• Poor performance

• Safety hazards

Use the right licensed professional.

Final verdict: should you buy a Rheem instant gas hot water system?

A Rheem instant gas hot water system can be a strong option for homes already set up for natural gas or LPG, especially where the household wants compact continuous flow hot water and the correct flow rate can be installed safely.

It is best suited to properties with suitable gas pipe sizing, water pressure, outdoor wall space and licensed gas fitting access. It may be less suitable for homes without gas, homes with weak water pressure, properties wanting to avoid gas long term, or customers who may be better served by heat pump hot water.

Before ordering, compare Rheem with other gas and hot water options. Start with Rheem hot water systems, instant gas hot water systems, gas hot water systems, Rinnai hot water systems, Bosch hot water systems and heat pump hot water systems.

The right system is the one that matches your gas type, household demand, installation location, water pressure and long-term running cost goals.

Long-tail FAQs

Are Rheem instant hot water systems good?

Rheem instant gas hot water systems can be a good option for homes with suitable natural gas or LPG supply, correct water pressure and professional installation. They should be compared by flow rate, gas type, warranty and total installation requirements.

What size Rheem instant gas hot water system do I need?

The right size depends on the number of bathrooms, number of people, shower habits, water pressure, incoming water temperature and whether multiple outlets may run at the same time.

Is a Rheem 26L instant gas system good for two bathrooms?

A 26L system is commonly compared for two-bathroom homes, but it still needs suitable gas pipe sizing, water pressure and installation conditions. A licensed gas fitter should confirm suitability.

Does Rheem instant gas use natural gas or LPG?

Rheem gas hot water systems may be available in natural gas or LPG versions depending on the model. Natural gas and LPG are not interchangeable, so the correct model must be selected.

Does Rheem instant gas need electricity?

Many continuous flow gas systems need electricity for ignition, controls and safety features. Check the model requirements before ordering.

Why does instant gas hot water take time to reach the tap?

The system heats water on demand, but hot water still has to travel through the pipework. Longer pipe runs can create a delay at showers and taps.

Can Rheem instant gas run two showers at once?

It depends on the model flow rate, gas supply, water pressure and shower flow rates. A larger flow rate may be required, but the installation setup must support it.

Is Rheem better than Rinnai instant gas?

Rheem and Rinnai both offer instant gas hot water options. Compare the exact models by flow rate, gas type, warranty, controller options, installation requirements and total replacement cost.

Is instant gas cheaper to run than electric storage?

Instant gas may cost less to run than some electric storage systems in certain homes, but the result depends on gas prices, electricity tariffs, household usage, system efficiency and installation cost.

Should I choose Rheem instant gas or heat pump hot water?

Choose Rheem instant gas if your home is already suited to gas continuous flow. Compare heat pump hot water if you want an efficient electric option and have suitable outdoor space, airflow, drainage and electrical setup.