G12/AS1 Water Supplies
One water heater checked against G12/AS1: the temperature it delivers and stores, its relief valve drain, its safe tray, its seismic straps and an open vented heater's vent pipe; and every document's sizes for it, NZS 4305's run to the sink and a gas heater's flue terminal among them. Then G12/AS1's requirements for water tanks, water heaters, hot water temperatures and accessible taps, and what the drawings show for each.
- G12/AS1Third Edition Amendment 142 Nov 2024
- NZS 4121:2001
- NZS 4305:1996
- AS/NZS 5601.1:2013
- Kāinga Ora v2.1
One water heater
What a water heater delivers and stores, how far its relief valve drain runs, its safe tray and seismic straps, and an open vented heater's vent pipe.
Who the building is for
The heater
Relief valve drain and safe tray
Seismic restraint
What this water heater needs
- Delivered, at most
- 50°C
- 6.14.1
- Thermostat, at least
- 60°C
- 6.14.3
- Straps
- 2
- Figure 14
Delivered
50 degrees at the fixtures, no hotter than 50.
6.14.1 b)
Stored
Thermostat at 60 degrees, at least 60.
6.14.3
Temperature control
Stored hotter than the 50 degrees it may be delivered at, so a temperature control device from Table 8B stands between the heater and the fixtures.
6.14.2, Table 8B
Relief valve drain
4 metres and 3 changes of direction count 7, no more than 12.
6.7.2 f)
Safe tray drain
40 mm across, at least 40 mm.
6.11.3 a), 5.2.3
Drain pipe
At 180 litres, more than 45, the heater has a drain pipe to empty it.
6.11.3 c)
Seismic straps
2 straps, as Figure 14 counts them for 180 litres.
6.11.4, Figure 14
Say what kind of heater it is and what it serves, and each size shows what every document asks of it and which of them binds.
This one
Kind of water heater
How it is vented
Its energy
Pipe from the heater to the kitchen sink
Client and rating standards
The sizes an answer changes are listed here and drawn darker. Point at an answer to see what it would change.
Hot water at the outlets
≤ 50 °C
- G12/AS1 6.14.1 b)≤ 50 °CAt a basin, shower, bath or bidet used for personal hygiene.
- G12/AS1 6.14.1 a)≤ 45 °CIn an early childhood centre, school, old people's home, hospital or institution for people with disabilitiesAt a basin, shower, bath or bidet used for personal hygiene.
- Kāinga Ora v2.1 C1.5.2 B45 - 50 °CFor a Kāinga Ora home
1 more set it elsewhere
- Kāinga Ora v2.1 C1.5.2 G45 °CFor a Kāinga Ora home and at the hand basins of a communal facility
Thermostat setting
≥ 60 °C
- G12/AS1 6.14.3≥ 60 °C
Seismic strap from the top or bottom
≤ 100 mm
- G12/AS1 Figure 14 Note 4≤ 100 mmFor a storage water heater of up to 360 litres, the largest Figure 14's straps are forOr, where a strap cannot sit this close, more straps within the top and bottom quarters of its height.
Fittings through the platform, clear of its support
≥ 50 mm
- G12/AS1 6.11.4≥ 50 mmWhere fittings and pipes pass through the platform or floor the heater stands on.
Safe tray drain
≥ 40 mm
- G12/AS1 5.2.3≥ 40 mm
Pressure relief valve from the heater
≤ 1 m
- G12/AS1 6.6.5 b)≤ 1 m
- NZS 4305:1996 3.3.1≤ 1 mFor a storage water heater of up to 700 litres, which H1/AS1 3.1.1.1 sends to NZS 4305Where the valve is not fitted to the heater: the pipe between them.
Pipe to the tempering valve
≥ 1 m
- G12/AS1 Figure 16≥ 1 m
Pipe run to the kitchen sink
≤ 12 m
- NZS 4305:1996 Table 5≤ 12 mFor a storage water heater of up to 700 litres (H1/AS1 3.1.1.1), or a Kāinga Ora home (C1.5.2 E)
- NZS 4305:1996 Table 5≤ 25 mFor 10 mm pipe
- NZS 4305:1996 Table 5≤ 7 mFor 20 mm pipe
Hot pipe insulated from the heater
≥ 2 m
- NZS 4305:1996 3.7.1 (a)≥ 2 mFor a storage water heater of up to 700 litres, which H1/AS1 3.1.1.1 sends to NZS 4305Or to the first drop in the pipe that makes a heat trap.
Drop that makes a heat trap
≥ 250 mm
- NZS 4305:1996 3.7.1 (c)≥ 250 mmFor a storage water heater of up to 700 litres, which H1/AS1 3.1.1.1 sends to NZS 4305Where the insulation stops at a heat trap rather than after the first horizontal run.
Insulation past the heat trap's top
≥ 150 mm
- NZS 4305:1996 3.7.1 (c)≥ 150 mmFor a storage water heater of up to 700 litres, which H1/AS1 3.1.1.1 sends to NZS 4305Where the insulation stops at a heat trap rather than after the first horizontal run.
Relief valve drain, bends and metres together
≤ 12
- G12/AS1 6.7.2 f)≤ 12Each change of direction counted as one, added to the drain's length in metres.
Cylinder's heat loss in a day
≤ 1.6 kWh
- NZS 4305:1996 Table 1≤ 1.6 kWhFor a storage water heater of up to 700 litres, which H1/AS1 3.1.1.1 sends to NZS 4305
Relief valve probe from the cylinder's top
≤ 150 mm
- G12/AS1 6.6.5 a)≤ 150 mm
Energy cut-off temperature
≤ 95 °C
- G12/AS1 6.5.2≤ 95 °C
Cylinder size that has a drain pipe
> 45 L
- G12/AS1 6.11.3 c)> 45 L
Cylinder Figure 14's restraint suits
≤ 360 L
- G12/AS1 6.11.4≤ 360 L
Straps within the top and bottom share
≤ 25 %
- G12/AS1 Figure 14 Note 4≤ 25 %For a storage water heater of up to 360 litres, the largest Figure 14's straps are for
Cylinder size that has a centre strap
> 200 L
- G12/AS1 Figure 14> 200 LFor a storage water heater of up to 360 litres, the largest Figure 14's straps are for
Height above the ground that adds a centre strap
> 12 m
- G12/AS1 Figure 14 Note 1> 12 mFor a storage water heater of up to 360 litres, the largest Figure 14's straps are for
Straps on a cylinder, most
≤ 4
- G12/AS1 Figure 14 Note 5≤ 4For a storage water heater of up to 360 litres, the largest Figure 14's straps are for
Sizes not set for this one
No document sets these for the answers above. Beside each is what would bring it in; open one to see who sets it.
Storage capacityFor a Kāinga Ora home
Storage capacity
Nothing any document asks, for this one.
- Kāinga Ora v2.1 Table C1.5-1≥ 135 LFor a Kāinga Ora homeFive or more bedrooms may split it across two cylinders.
Vent pipe water level above the highest outletFor an open vented heater
Vent pipe water level above the highest outlet
Nothing any document asks, for this one.
- G12/AS1 6.8.2 e)≥ 3 mFor an open vented heater
Vent pipe above its water levelFor an open vented heater fed from a header tankor for an open vented heater fed through a pressure reducing valve
Vent pipe above its water level
Nothing any document asks, for this one.
- G12/AS1 6.8.2 e) i)≥ 300 mmFor an open vented heater fed from a header tank
- G12/AS1 6.8.2 e) ii)≥ 1000 mm (1 m)For an open vented heater fed through a pressure reducing valve
Vent pipe insulated above its water levelFor an open vented heater
Vent pipe insulated above its water level
Nothing any document asks, for this one.
- NZS 4305:1996 3.5.1≥ 300 mmFor an open vented heater
1 more set it elsewhere
- G12/AS1 6.8.3 a)≥ 300 mmFor an open vented heater and where the vent pipe could freeze
Water in a run of mixed pipe sizesFor a run of more than one pipe size
Water in a run of mixed pipe sizes
Nothing any document asks, for this one.
- NZS 4305:1996 3.2.1≤ 2 LFor a run of more than one pipe size
Vent pipe diameterFor an open vented heater
Vent pipe diameter
Nothing any document asks, for this one.
- G12/AS1 6.8.2 b)≥ 20 mmFor an open vented heaterWhere the heater's energy input rating is over 3 kW.
Element size, each cylinderFor a Kāinga Ora home
Element size, each cylinder
Nothing any document asks, for this one.
- Kāinga Ora v2.1 Table C1.5-12 - 2 kWFor a Kāinga Ora home
Cylinder cupboard widthFor a Kāinga Ora home
Cylinder cupboard width
Nothing any document asks, for this one.
- Kāinga Ora v2.1 Table B2.4-2≥ 700 mmFor a Kāinga Ora home
Cylinder cupboard depthFor a Kāinga Ora home
Cylinder cupboard depth
Nothing any document asks, for this one.
- Kāinga Ora v2.1 Table B2.4-2≥ 800 mmFor a Kāinga Ora home
Gas water heater's thermal efficiencyFor a gas water heater
Gas water heater's thermal efficiency
Nothing any document asks, for this one.
- NZS 4305:1996 Table 3≥ 75 %For a gas water heater
2 more set it elsewhere
- NZS 4305:1996 Table 3≥ 75 %For a gas water heater and not for a storage water heaterIn NZS 4305's own scope; H1/AS1 3.1.1.1 sends only storage heaters to it.
- NZS 4305:1996 Table 3≥ 70 %For a gas water heater and cond.gasBig
Gas a storage heater burns to keep hotFor a gas water heater
Gas a storage heater burns to keep hot
Nothing any document asks, for this one.
- NZS 4305:1996 Table 4≤ 0.27 kWFor a gas water heater
1 more set it elsewhere
- NZS 4305:1996 Table 4≤ 0.35 kWFor a gas water heater and cond.gasBig
G12 requirements
The requirements of G12/AS1 this tool reads, numbered, so one can be pasted onto a sheet as it stands: water tanks, water heaters, hot water temperatures and accessible taps. Where the document states a condition, it can be answered N/A, and the answer prints.
Water storage
- Cold water storage Cold water storage of at least 50 litres for each person.
5.1.1
Water tanks
where the building has a water tank5.2.2
- Tanks in the roof A water tank in a roof space located and supported as Figure 4 details.
5.2.1, Figure 4
- Overflow An overflow pipe from the tank that discharges somewhere visible on the same property, where it causes no nuisance or damage; sized to carry at least the most the tank takes in, with an outlet birds and vermin cannot get into.
5.2.2
- Safe tray A safe tray under the tank with a drain at least 40 mm across, and bigger than the tank's overflow pipe where the overflow runs into it.
5.2.3, Figure 4
- Covers A cover on a drinking water tank to keep it clean and vermin out, and on every tank in a roof space to stop condensation damaging the building.
5.2.4
- Access A removable cover, or a covered opening in it, for inspection and maintenance, with 350 mm of clear height above the opening.
5.2.5
- What it stands on The tank's supports protected from condensation where it could harm them, with a material such as H3 treated timber under the tank.
5.2.6
- Seismic restraint The tank supported and restrained against earthquakes. Figure 4's method suits tanks of up to 150 litres whose height is no more than 1 times their breadth.
5.2.7, Figure 4
- Disinfection A drinking water tank cleaned and disinfected before it is used, as AS/NZS 3500.1 Appendix G sets out.
5.2.8
Relief valves
where there is a storage water heater6.11.3
- Temperature/pressure relief valve Its probe in the top 20% of the water and no more than 150 mm from the top of the container.
6.6.5 a)
- Pressure relief valve No more than 1 metre from the storage water heater.
6.6.5 b)
- Getting at them Every valve installed so it is easy to reach for replacement, servicing and maintenance.
6.6.5 c)
- Nothing in between No valve or restriction between the relief valve and the storage water heater.
6.6.6
Relief valve drains
where there is a storage water heater6.11.3
- Relief valve drains A drain from each temperature/pressure relief valve, pressure relief valve and expansion control valve.
6.7.1
- The drain Copper, with no restriction or valve, falling all the way from the valve to its outlet, and discharging somewhere visible where it is no hazard and damages nothing; at least as big as the valve's outlet, connected as the valve's maker says, and with its changes of direction and its length in metres adding up to no more than 12.
6.7.2
- Combined drains A combined drain takes one temperature/pressure relief valve, or the pressure relief valve and one expansion control valve, discharges through an air break of at least 25 mm, and is at least 20 mm across and one size bigger than the largest valve outlet it takes.
6.7.3, Figure 13
- A heater where it can freeze Each relief valve drain takes one valve only.
6.7.4, Figure 12
- A drain where it can freeze The drain discharges over a tundish, through an air break of 25 mm, before it reaches where freezing is likely, and the drain from the tundish is one size bigger than the relief valve's outlet.
6.7.5, Figure 12
- Protecting the insulation Insulation that takes up moisture kept in a waterproof membrane, and insulation in the sun resistant to UV or protected from it.
6.7.7
Vent pipes
where the storage water heater is open vented6.8.1
- Material A copper vent pipe, as Table 1 lists.
6.8.1, 6.8.2 a)
- Diameter At least as big as the heater's hot water outlet, and at least 20 mm across where the energy input is over 3 kW.
6.8.2 b)
- Where it ends The vent pipe ends outside the building, or over the water tank that feeds the heater.
6.8.2 c), Figure 6
- Height The vent pipe no higher above the base of the heater than the head its maximum pressure rating equates to.
6.8.2 d)
- Standing water level The water standing in the vent pipe at least 3 metres above the highest outlet, and the vent pipe 300 mm above that level where it is tank fed, or 1 m above it where it is fed through a pressure reducing valve.
6.8.2 e)
- Insulation A vent pipe likely to freeze insulated from the top of the heater to at least 300 mm above its standing water level.
6.8.3
Installing the water heater
A storage water heater keeps its water; an instantaneous one heats it as it flows. Where there is no storage water heater, most of this section can be answered N/A.
- The maker's instructions Water heaters installed as their manufacturer instructs.
6.11.1
- Getting at the parts The heating units, anodes, thermostats, connections, valves and other parts of a storage water heater within reach for inspection, maintenance and removal.
6.11.2
- Safe tray A safe tray under the storage water heater, with a drain at least 40 mm across.
6.11.3 a), 5.2.3
- Connections Connections that suit the pipe material.
6.11.3 b)
- Emptying it A storage water heater of more than 45 litres has a drain pipe, either with an isolating valve and a cap or plug where the heater can easily be emptied, or ending outside the building with a cap.
6.11.3 c)
- Seismic restraint The storage water heater supported and restrained against earthquakes. Figure 14's method suits heaters of up to 360 litres; where fittings and pipes pass through the platform or floor it stands on, 50 mm clear between them and the structure.
6.11.4, Figure 14
- Straps Figure 14's straps within 100 mm of the top and bottom, with a centre strap for a heater over 200 litres and another where it stands more than 12 m above finished ground; where the straps cannot sit that close, they go in the top and bottom 25% with more between, and never more than 4 in all.
Figure 14
- Wet-backs A wet-back designed and installed to NZS 4603 Part 4, connected only to an open vented storage water heater or storage vessel, with a copper wet-back and copper pipes to the water tank.
6.13.1, Figure 15
Safe water temperatures
- Hottest water delivered Water at the outlet of a basin, shower, bath or other fixture used for personal hygiene no hotter than 45 degrees in early childhood centres, schools, old people's homes, institutions for people with psychiatric or physical disabilities and hospitals, and 50 degrees in every other building.
6.14.1
- Controlling it A device that limits the temperature delivered, of a kind Table 8A lists where the limit is the lower one and Table 8B where it is the higher.
6.14.2, Table 8A, Table 8B
- Stored hot enough The storage water heater's thermostat set to at least 60 degrees, against Legionella, whether or not a temperature control device is fitted.
6.14.3
- Before the valve At least 1 m of copper pipe between the storage water heater and its temperature control device.
Figure 16
- Uncontrolled heat No untempered hot water to any fixture or appliance from a storage water heater heated by a wet-back, a solar water heater or another heat source that is not controlled.
Figure 16
Taps for people with disabilities
- Accessible taps Single lever handles, or sensor plates that turn the water on when hands are put under them; at least 50 mm clear between the lever, in every position, and any surface beside it; hot to the left and cold to the right.
8.0.1, Figure 18
G12 requirements to show on the drawings
What has to be drawn or named for each requirement to be checkable. It follows the answers on Requirements, and what was answered N/A is recorded above the list.
Show on the drawings
- 5.1.1
- 5.2, Figure 4
- 6.11
- 6.11.4, Figure 14
- 6.7, Figures 12 and 13
- 6.7.7, 6.8.3
- 6.8
- 6.13.1
- 6.14, Figure 16
- 6.14.3
- 8.0.1, Figure 18
Terminology
The words the requirements lean on, as G12/AS1 defines them.
- Air gapDefinitions
- The vertical distance through air between the lowest point of a water outlet and the flood level rim of the fixture or equipment it discharges into.
- Free outletDefinitions
- A storage water heater with a tap on its cold water inlet, which pushes the hot water out through an open outlet.
- Open vented storage water heaterDefinitions
- A water heater with a vent pipe permanently open to the air.
- Sanitary fixtureDefinitions
- Any fixture meant for sanitation.
- Storage water heaterDefinitions
- A water tank with its own water heater, for storing hot water.
- Valve vented storage water heaterDefinitions
- A storage water heater whose venting to the air is controlled by a valve; also called unvented.
- Vent pipeDefinitions
- A pipe open to the air at one end, which limits the pressure.
- Water heaterDefinitions
- A device for heating water.
Reading G12
Why the document says what it says: its COMMENTs, where its figure and paragraph name different ranges, and where NZS 4121 still gives an older temperature. It does not print.
Water storage
- Why storage5.1.1 COMMENT
- The COMMENT says it is for personal hygiene where the people inside are legally or physically confined, because the water main cannot be guaranteed. Other buildings may store water for their own reasons.
Water tanks
- Where the overflow can go5.2.2 COMMENT
- The COMMENT's places: into the safe tray over its drain, straight into the safe tray's drain pipe, onto an impervious floor that falls to a floor waste, or outside clear of doors, windows and other openings.
Relief valve drains
- Counting the drain6.7.2 f) COMMENT
- The COMMENT's example: 7 metres of pipe leaves room for 5 bends.
- Where it can discharge6.7.2 d) COMMENT
- The COMMENT's examples are through an air break into a gully trap outside, or through an air break into a tundish in a cupboard.
- Insulation against freezing6.7.6
- Closed cell foam or fibreglass preformed to the pipe, at least 13 mm thick, is acceptable for pipes up to 40 mm across.
Vent pipes
- Why those heights6.8.2 COMMENT
- The COMMENT: the extra height on a pressure reducing valve stops hot water being lost when the valve creeps, the standing level gives the highest fitting enough head, and 9.81 kPa is a metre of head.
Installing the water heater
- Which heaters Figure 14 covers6.11.4, Figure 14
- 6.11.4 says Figure 14's method suits heaters up to 360 litres, and the figure's title names 90 to 360 litres. The page counts straps for any heater up to 360 litres and says when it is under 90.
- Other acceptable solutions6.9.1, 6.10.1
- NZS 4603 is an acceptable solution for open vented, low pressure storage water heaters, and NZS 4607 for valve vented ones; either may ask for more than the Code does.
Safe water temperatures
- Early childhood centres6.14.1 COMMENT
- The COMMENT: to be licensed, an early childhood centre keeps the water from taps children can reach at 40 degrees or less, which is the Ministry of Education's figure, lower than G12/AS1's.
- NZS 4121's figure is out of date6.14.1, NZS 4121 10.5.8.2 (b), NZS 4121 10.5.11.4 (e)
- NZS 4121 puts the hottest water at an accessible basin and shower at 55 degrees and refers to G12/AS1 for it. G12/AS1 now caps it at 50 degrees, and at 45 in the buildings where people are cared for, so the lower figure governs.
Taps for people with disabilities
- Which buildings8.0.1 COMMENT
- The COMMENT says it does not apply to Housing, Outbuildings, Ancillary buildings, or Industrial buildings employing fewer than 10 people.
- Beside NZS 41218.0.1 b), NZS 4121 10.5.8.2 (c)
- NZS 4121 keeps an accessible basin's controls 50 to 60 mm clear of anything around them, which also meets G12/AS1's 50 mm.
Where the rest is
What this page reads, and what it points at rather than reads.