930004NT Temperature and Pressure Relief Valve
The Legom 930004NT Pressure & Temperature Relief Valve (PTR Valve) is a premium dual automatic safety device for boilers, water heaters, and controlled pressure storage water heaters, compliant with AS1357.1 and certified to WaterMark (WM-032219) for the Australian and New Zealand market. When water temperature reaches 93–99°C or system pressure reaches the rated setting, the internal wax probe automatically opens to release hot water and steam through the discharge line. When conditions return to safe levels, the valve resets automatically — with a resetting pressure of ≥90% of opening pressure, the tightest reset tolerance in the Legom PTR valve range.
Available in two sizes — 930007NT (DN15 / 1/2″) and 930004NT (DN20 / 3/4″) — with seven pressure rating options from 500 kPa to 1400 kPa and expansion ratings of 10 kW (DN15) and 46 kW (DN20). All water-contacting metal components are manufactured from DZR (dezincification-resistant) brass, extending service life in potable water environments compared to standard brass. The proprietary “dry type” spring structure physically isolates the spring mechanism from the relief water flow, preventing sediment adhesion to the spring that could cause pressure measurement errors and valve malfunction.
Key Benefits
- AS1357.1 compliant and WaterMark certified (WM-032219) – Certified to the Australian standard for PTR valves and carries WaterMark approval, confirming compliance with Australian/New Zealand plumbing regulations and AS/NZS3500 installation requirements
- DZR brass on all water-contacting components – Dezincification-resistant brass throughout prevents the selective zinc leaching that degrades standard brass in potable water, extending valve service life particularly in soft water, hard water, and high-chloride environments common in Australian water supplies
- “Dry type” spring isolation structure – A rubber ring seal physically separates the spring and other internal components from the hot water discharge flow, preventing sediment from adhering to the spring surface during relief events. Sediment on the spring changes its effective stiffness and can cause the valve to malfunction — the dry type design eliminates this failure mode entirely
- Resetting pressure ≥90% of opening pressure – Tighter reset tolerance than the 930008NT series (≥85%), ensuring the valve closes more decisively and completely after a relief event, minimizing post-event weeping
- Strong scale tolerance — sealing unaffected by scale deposits – Internal waterway size and structure are designed to drain water and scale quickly after pressure relief, and the valve seal maintains integrity even as scale accumulates on internal surfaces over time
- Precise reset guiding mechanism – Enables fast, complete automatic reset even after large pressure relief events, restoring watertight sealing without manual intervention
- Seven pressure rating options: 500–1400 kPa – Covers the full range of domestic and commercial water heater pressure ratings for correct vessel-matched installation
- Expansion ratings: 10 kW (DN15) and 46 kW (DN20) – Published expansion ratings enable correct valve selection based on water heater element rating, as required by AS1357.1 and water heater manufacturer installation requirements
Technical Specifications
| Parameter | Specification |
|---|---|
| Water-touching Materials | DZR Brass |
| Opening Temperature | 93°C – 99°C |
| Resetting Temperature | ≥ 70°C |
| Pressure Ratings Available | 500 / 600 / 700 / 850 / 1000 / 1200 / 1400 kPa |
| Resetting Pressure | ≥ 90% of opening pressure |
| Standards | AS1357.1 |
| Certification | WaterMark WM-032219 |
| Installation Standard | AS/NZS3500 |
Model Variants, Dimensions and Expansion Ratings
| Model | Size | A (mm) | C (mm) | D (mm) | Thread (F) | Expansion Rating |
|---|---|---|---|---|---|---|
| 930007NT | DN15 (1/2″) | Ø37 | 51 | 94 | R1/2″ | 10 kW |
| 930004NT | DN20 (3/4″) | Ø37 | 41 | 105 | R3/4″ | 46 kW |
The kW expansion rating of the valve must be equal to or greater than the kW rating of the water heater. Confirm the water heater’s rating plate before selecting valve size.
Application & Use Cases
- Australian and New Zealand water heater installations – The WaterMark certification and AS1357.1 compliance make the 930004NT/930007NT the correct product for all PTR valve installations in Australia and New Zealand, where WaterMark-approved products are legally required in regulated plumbing work
- Domestic storage water heaters – The 10 kW expansion rating of the DN15 variant covers standard domestic electric water heater element ratings in single-element storage units
- Commercial storage water heaters and boilers – The 46 kW expansion rating of the DN20 variant covers larger commercial electric storage vessels and gas-boosted systems requiring higher-capacity PTR protection
- Solar hot water storage systems – WaterMark-certified PTR valves are required on AS/NZS3500-compliant solar thermal storage vessel installations. The DZR brass construction provides additional corrosion resistance in solar systems where water chemistry can be aggressive
- Heat pump hot water systems – Required as a mandatory safety component on all pressurized heat pump storage vessels installed under AS/NZS3500
Installation Notes
- Must be installed by a licensed plumber in accordance with AS/NZS3500 National Plumbing and Drainage Code and all applicable local government requirements. The valve must be installed in line with the water heater manufacturer’s instructions
- The kW expansion rating of the valve must equal or exceed the kW rating of the water heater. This information is on the rating plate of the valve and the rating label on the water heater. Never install a valve with an expansion rating lower than the heater’s rated element output
- Apply thread seal tape to the thread. Do not use excessive amounts — excess tape can break off, lodge under the valve seat, and cause the valve to leak
- Screw the valve into the PTR socket using the spanner flats provided. Do not use a wrench on the valve body — this can damage the brass body and compromise the valve’s structural integrity
- No valves, taps, or isolating devices may be fitted between the PTR valve and the water heater — any obstruction between the valve and the vessel prevents the valve from protecting the vessel
- Install a discharge drain line of the same nominal pipe size as the valve, in accordance with AS/NZS3500.4. The drain line must have a continuous fall to a safe discharge point. Do not reduce the drain line diameter
- If the wax probe is damaged in any way, do not install the valve. Return it to the supplier for replacement
- Flush all lines before installation to remove debris that could lodge under the valve seat
- Test the manual relief lever every 6 months by lifting the lever — water should flow from the relief valve. This flushes deposits that may accumulate under the seal. Confirm the discharge line is connected before testing. Caution: discharged water is hot — danger of scalding.
Frequently Asked Questions
What is the difference between the 930004NT and the 930008NT?
Both are PTR valves providing dual temperature and pressure protection for water heaters and boilers, with identical size options, pressure rating ranges, and wax probe actuation. The key differences are: the 930004NT/930007NT complies with AS1357.1 and carries WaterMark certification for the Australian/New Zealand market, while the 930008NT/930003NT complies with ANSI Z21.22 and EN1490 for North American and European markets. The 930004NT also uses DZR brass on all water-contacting components versus standard brass, has a tighter resetting pressure of ≥90% versus ≥85%, and incorporates the “dry type” spring isolation structure that prevents sediment-related spring malfunction. Choose the 930004NT for Australian/New Zealand installations; choose the 930008NT for North American or European projects.
What does the “dry type” spring structure mean and why does it matter?
In a conventional PTR valve, the spring that controls pressure sensing is in direct contact with the water discharged during a relief event. Scale and sediment carried in the relief water can deposit on the spring surface, changing the spring’s effective stiffness over time. If the spring becomes stiffer from scale buildup, the valve may fail to open at the rated pressure — a serious safety failure. The 930004NT’s “dry type” structure uses rubber ring seals to physically isolate the spring from the relief water path. Relief water cannot reach the spring, so scale cannot deposit on it, and the spring’s calibration remains accurate throughout the valve’s service life.
What is WaterMark certification and why is it required in Australia?
WaterMark is a mandatory certification scheme administered by the Australian Building Codes Board (ABCB) for plumbing and drainage products used in regulated plumbing work in Australia. Products must be certified to relevant Australian Standards and carry a valid WaterMark licence before they can be legally installed by licensed plumbers in Australia. The 930004NT carries WaterMark licence WM-032219, confirming it meets AS1357.1 requirements and can be lawfully installed in Australian plumbing systems.
How do I select the correct model and pressure rating?
First, match the valve size to the water heater connection: use 930007NT (DN15/1/2″) for heaters up to 10 kW and 930004NT (DN20/3/4″) for heaters up to 46 kW. The kW rating of the valve must equal or exceed the kW rating on the heater’s rating plate. Second, select the pressure rating that matches or is below the water heater’s maximum allowable working pressure from the seven available options (500–1400 kPa). Both pieces of information are on the heater’s rating label.
How often should the valve be tested?
The manual relief lever should be operated every 6 months to flush deposits that may accumulate under the valve seat. Always confirm the discharge drain line is connected and directed to a safe location before operating the lever — the discharged water is hot and can cause scalding. If no water flows when the lever is lifted, the valve is inoperative. Shut off the water heater immediately and contact a licensed plumber.
OEM & ODM Customization
Legom supports OEM and ODM services for the 930004NT/930007NT Pressure & Temperature Relief Valve. Pressure ratings, thread specifications, and expansion ratings can be customized for specific vessel and market requirements. All customization projects are handled with strict confidentiality. Contact us via WhatsApp or info@legomsmart.com.
Datasheet
Product information last reviewed by the Legom Technical Team. For the most current specifications, refer to the official datasheet or contact our sales team.
Custom OEM & ODM Solutions
Legom is a direct manufacturer offering end-to-end OEM and ODM services. With our in-house engineering and production capabilities, we work closely with distributors and system integrators to deliver fully customized solutions under strict NDA.
