A hot water recirculation system keeps heated water moving around a loop of pipe and back to the heater through a return line, so hot water reaches the tap within seconds instead of after a long wait. In Victoria it is a plumbing job that must be designed to the national standard and installed by a licensed plumber. In aged care, retirement villages and disability homes, the loop also has to hold safe temperatures at every outlet. We are DualFlow Services, a plumbing, electrical and heating and cooling team on the Mornington Peninsula, and this guide explains how a loop works and what to plan for.
TL;DR
- A recirculation loop pumps water around the hot pipes and returns the cooled water to the heater, so hot water is ready at the outlet sooner.
- A pump alone is not the whole system. Pipe sizing, insulation, return temperature and balancing decide whether it works and stays safe.
- Victorian rules limit water velocity in loop pipework and cap delivery temperature at 45°C at fixtures in the residential parts of aged care buildings.
- Continuous loops cost energy through pump power and pipe heat loss. Timers, sensors and on-demand controls reduce it.
- Only a licensed plumber can do this work and issue the compliance certificate.
Table of Contents
- What hot water recirculation actually does
- The main types of system
- Where the loop earns its keep
- Temperatures that keep the loop safe
- Pump, pipe and control choices that decide performance
- What it costs to run, and how to control it
- Common problems and what they point to
- The Victorian rules in short
- A practical path from idea to working loop
- Where we come in
- Our view on recirculation
- FAQ
- Sources
What hot water recirculation actually does
Without a loop, the hot pipe from your heater to a distant bathroom or kitchen fills with water that cools between uses. You open the tap and run that cold water down the drain until fresh hot water arrives. The longer the pipe, the longer the wait and the more water wasted.
A recirculation system fixes this by keeping water moving. The Australian Building Codes Board handbook on warm water systems explains that circulatory systems are commonly used to cut the time heated water takes to reach the outlet. Heated water is circulated through the system and cooler water is returned to the heating plant by a pump, usually fitted on the cooler return line. A check valve can stop water flowing backwards through the pump when it is not running.
That return line is why people search for a hot water return line or a hot water loop. It is the second pipe that completes the circuit. A loop built this way is what many call instant hot water, although in practice the wait is short rather than zero.
The main types of system
The same idea comes in several forms. Which one suits you depends on the building.
| Type | How it works | Where it fits |
|---|---|---|
| Dedicated return line (loop) | A separate return pipe carries cooled water back to the heater | New builds, renovations, commercial and care buildings |
| Single pipe circulating system | One circulating main serves many outlets from a central plant | Commercial buildings and high-rise apartments, according to the ABCB handbook |
| Two pipe direct return | One main delivers heated water, a second returns it | Larger buildings with several branches |
| Two pipe reverse return | Flow and return pipe lengths are equal, giving an even flow to every branch | Buildings where branches must be balanced |
| On-demand system | Triggered by a tap, switch or sensor | Homes where a loop is needed only at set moments |
The NSW Planning Portal describes the control options well. On-demand systems start when someone operates a tap, a switch or a sensor. Continuous or timed systems circulate water all the time or for a set period each day. The portal is a New South Wales source, but the control types are the same in Victoria.
In an existing home with no return pipe, a plumber can sometimes use a retrofit arrangement instead. Whether that is possible depends on the pipe layout, so it is a decision for a site visit rather than a guess.
Where the loop earns its keep
Large homes and long pipe runs
In a house where the heater sits far from the main bathroom, waiting for hot water becomes a daily annoyance. As a guide, CCC Engineering advises fitting a circulation pump and return loop where pipe runs exceed about 12 metres. Many Peninsula homes with an extension, a granny flat or a second level reach that length easily.
Businesses
Cafés, restaurants, gyms and accommodation need hot water at the tap straight away, and customers notice when it is not there. Our guide to hot water temperatures for restaurants covers the temperature side, and a loop is often how that temperature is held across a long kitchen or a multi-room building.
Aged care, retirement villages and disability homes
Here a loop is about safety as much as comfort. The same CCC Engineering guidance notes that where water sits in pipes and cools below 55°C, Legionella risk and user complaints follow. Residents are often more vulnerable to both infection and scalding, so a well-built loop has to deliver water that is hot enough in the pipes and safe at the outlet. Our guides on plumbing compliance in aged care facilities and plumbing upgrades for disability homes go deeper on those settings. Where several buildings share one plant, a centralised hot water system is often paired with a loop.
Temperatures that keep the loop safe
Two numbers matter in a recirculating system: the temperature leaving the heater and the temperature coming back.
Plumbing Connection's explanation of AS/NZS 3500.4 states that water leaving a heater should be at least 60°C and water returning to the heater at least 55°C. The ABCB handbook says the return pipe usually shows a 3°C to 5°C drop depending on the length of the circuit. If the return falls much below 55°C, the loop is losing too much heat or the flow is too low, and bacteria can colonise the pipework, as CCC Engineering explains.
Hot enough in the pipe is only half of it. The Victorian provisions of the National Construction Code require the delivery temperature at each sanitary fixture to be no more than 45°C in any residential part of an aged care building, early childhood centre, or primary or secondary school used by children. The usual way to reconcile the two is to store and circulate hot, then temper the water before it reaches the fixture. Our guide to hot water temperature and scalding prevention explains tempering for homeowners.
Pump, pipe and control choices that decide performance
A recirculation pump is small, but a poor choice causes problems across the whole system.
Pump size. The ABCB handbook says pumps need enough pressure and flow for the system. An undersized pump can leave the heating plant running at a much higher and fluctuating temperature. An oversized pump can cause excessive water velocities if there are no balancing valves.
Water velocity. Fast water erodes pipework. The Victorian NCC provisions set limits for heated water pipework up to 65°C. For a copper circulatory service, flow velocity must not exceed 1.2 m/s and return velocity 1.0 m/s. For other pipe materials, both flow and return are limited to 1.0 m/s. AS/NZS 3500.4:2021 sets 1.0 m/s for the return line of any material.
Insulation. Plumbing Connection notes that recirculation pipes are always insulated. CCC Engineering's pipe calculator, which references the 2021 standard, gives a minimum insulation R-value of 0.6 for these pipes, and typical heat loss for insulated copper from about 8 W/m for DN15 to 20 W/m for DN50. Those losses run around the clock on a continuous loop, which is why insulation quality matters.
Pipe layout. Plumbing Connection explains that loop piping is sized on loading units and index length like cold water, while the return is sized on circulation flow only. CCC Engineering recommends running the loop through all branches and fitting balancing valves on each riser so every branch gets flow.
Dead legs. The ABCB handbook warns that stand-by pumps and hammer arrestors can create dead legs, which are stretches of pipe where water stagnates and microbes can grow. A good design avoids them.
Access. Victorian rules require access to the heated water service for maintenance of mechanical components and operational controls. Put the pump somewhere a plumber can reach it.
What it costs to run, and how to control it
A loop is never free to run. The pump uses electricity and the pipes lose heat, and the heater works to replace it. The NSW Planning Portal notes that continuous or timed systems will not improve a BASIX water rating because of their effect on energy use, while on-demand systems use a moderate amount of extra energy for pumping. That is a NSW rule about new homes, but the physics apply anywhere.
In practice, you control the cost three ways:
- Timers. Run the loop only during the hours hot water is needed, such as morning and evening in a home.
- On-demand triggers. A button, sensor or tap-activated pump runs the loop only when someone wants hot water.
- Insulation and sizing. Well-insulated pipes and a correctly sized pump cut the heat and power the loop wastes. For more on cutting energy use in pumped water equipment, see these energy-saving tips for pumps and heating.
For aged care and other facilities, a timer is rarely the right answer. Residents use hot water at all hours and the 55°C return temperature has to be maintained to manage Legionella risk, so these buildings generally run continuous loops and focus on insulation and efficient pumps instead.
Common problems and what they point to
| Symptom | Likely cause |
|---|---|
| Hot water still slow at the far tap | Unbalanced branches, undersized pump, or a tap not on the loop |
| Return temperature below 55°C | Poor insulation, low flow, or a heater not delivering 60°C |
| Noisy pipes or pinhole leaks over time | Water velocity too high, which erodes pipework |
| High power bills after installation | Continuous running with no timer, or an oversized pump |
| Hot water at the outlet too hot | Missing or failed tempering device |
Most of these come down to design and commissioning rather than a faulty pump. Balancing and testing the loop after installation is what separates a system that works from one that merely runs.
The Victorian rules in short
Plumbing in Victoria is regulated work. According to the Victorian Building Authority, a plumbing practitioner must be licensed and registered, or working under the supervision of a licensed plumber, and only a licensed plumber can issue a compliance certificate. Adding a recirculation line to your hot water system is plumbing work, so it needs a licensed plumber and a certificate at the end.
The design standard is AS/NZS 3500.4. The 2025 edition covers the design, installation and commissioning of heated water services, including alterations, additions and repairs to existing installations. The earlier 2021 edition changed requirements for circulated systems, including thermal insulation for non-circulatory piping and the maximum capacity of dead legs, to improve user amenity and reduce wastage of water and energy. The Victorian Plumbing Regulations 2018 have been amended several times, most recently from 1 May 2026, so the plumber you engage should work from the current versions.
For a business, the loop also sits inside wider obligations. Our guides to restaurant plumbing compliance cover the commercial side.
A practical path from idea to working loop
- Define the problem. Note which outlets wait longest, how far they are from the heater and when hot water is needed.
- Have the pipe layout assessed. A plumber checks whether a return line exists, whether one can be added and where the pump can go with proper access.
- Choose the system type and controls. Timer, on-demand or continuous, based on how the building is used.
- Design to the standard. Pump sizing, pipe velocities, insulation, balancing valves and tempering all follow AS/NZS 3500.4 and the Victorian NCC provisions.
- Install and commission. The loop is balanced, temperatures are checked at the heater, return and outlets, and the compliance certificate is issued.
- Maintain it. Pumps, valves and controls need periodic checks, which is where scheduled maintenance pays off.
Where we come in
DualFlow Services covers plumbing, electrical and heating and cooling under one roof on the Mornington Peninsula and surrounding Melbourne suburbs, for homeowners, business owners, aged care, retirement villages and disability care homes. A recirculation loop touches all of it: the pipework, the pump's power supply and controls, and the hot water plant. Having one team handle them reduces the handovers between trades. We offer plumbing and electrical work, scheduled maintenance, legal compliance checks, and emergency call-out around the clock, every day of the year.
If you want a loop assessed, or an existing one that is not delivering, talk to our team.
Our view on recirculation
Most loops we hear about fall short for ordinary reasons: the right pump on the wrong pipework, or good pipework with no balancing and no insulation to speak of.
For a home, we would start with how the household uses hot water and choose controls to suit. For a care facility, we would start with temperature: hot enough in the loop, safe at the outlet, and documented.
That is why we like to look after the plumbing, the electrical controls and the hot water plant together. One team, one plan, one set of records for a facility manager to hold.
Mike
FAQ
Is a hot water recirculation system worth it?
It is worth considering where pipe runs are long, waits are noticeable, or hot water has to be available at once, as in a business or care setting. Running costs depend on the controls, so a timer or on-demand trigger is usual in homes. A plumber can assess your layout before you commit.
Can I fit a recirculation pump myself?
No. In Victoria, plumbing work must be done by a licensed plumber, or someone working under a licensed plumber's supervision, and only a licensed plumber can issue the compliance certificate. The pump also needs to be sized and balanced correctly for the system.
Do I need a dedicated return line?
A dedicated return line is the standard way to build a loop, because it carries cooled water back to the heater. Some existing homes can be adapted with a retrofit arrangement, but that depends on the pipe layout and needs a site assessment.
What temperature should the loop run at?
Water should leave the heater at 60°C or more and return at 55°C or more. In the residential parts of aged care buildings, the delivery temperature at each fixture must not exceed 45°C, so tempering is part of the design.
Sources
- ABCB Handbook: Warm water systems
- NSW Planning Portal: Hot Water Recirculation Systems
- CCC Engineering: Domestic hot water plant sizing for commercial buildings
- CCC Engineering: Legionella risk in hot water systems
- CCC Engineering: Water pipe and pump sizing calculator
- Plumbing Connection: AS/NZS 3500.4 updates explained
- Plumbing Connection: Sizing and designing hot water recirculation systems
- NCC 2022 Victoria: Part B2 Heated water services
- Victorian Building Authority: Engaging a plumber
- Standards Australia: AS/NZS 3500.4:2021 preview
- Standards Australia: AS/NZS 3500.4:2025
- Plumbing Regulations 2018, Victorian legislation