930008NT Temperature and Pressure Relief Valve
The Legom 930008NT Temperature & Pressure Relief Valve (TPR Valve) is a dual-function automatic safety device designed to protect boilers, water heaters, and controlled pressure storage water heaters from the simultaneous hazards of excessive temperature and excessive pressure. When water temperature reaches 90–99°C or system pressure reaches the rated pressure setting, the internal wax probe automatically opens the seal mechanism to release hot water and steam through the discharge line — preventing catastrophic vessel failure. When temperature and pressure return to safe levels, the valve resets automatically.
Available in two sizes — 930008NT (DN15 / 1/2″) and 930003NT (DN20 / 3/4″) — with seven pressure rating options from 500 kPa to 1400 kPa, the valve complies with both ANSI Z21.22 (North American standard) and EN1490 (European standard), making it suitable for international project specifications. Manufactured from brass with a resetting pressure of ≥85% of the rated pressure, ensuring the valve closes decisively after a relief event without remaining in a partially open state.
Key Benefits
- Dual temperature and pressure protection in one valve – A single TPR valve protects against both overpressure and overtemperature simultaneously — the two primary failure modes of pressurized hot water storage systems. Either condition alone is sufficient to trigger relief
- Wax probe actuation for reliable temperature sensing – The wax probe directly senses water temperature inside the vessel at the installation point, providing accurate and responsive temperature-triggered relief without electrical dependency or calibration drift
- Seven pressure rating options: 500–1400 kPa – Covers the full range of domestic and commercial water heater pressure ratings, enabling correct valve selection matched to the specific vessel’s maximum allowable working pressure
- Automatic self-reset – The valve resets automatically when temperature drops to ≥70°C and pressure recovers to ≥85% of rated pressure, closing cleanly after a relief event without requiring manual intervention
- ANSI Z21.22 and EN1490 dual certification – Simultaneously certified to the primary North American and European standards for temperature and pressure relief valves, confirming performance across international regulatory environments
- Two sizes: DN15 (1/2″) and DN20 (3/4″) – Covering both the standard residential water heater connection size and the larger commercial storage vessel connection, with temperature steam ratings of 15,000 BTU/hr and 105,000 BTU/hr respectively
- Brass construction – Durable, corrosion-resistant body for long-term service in potable hot water environments
Technical Specifications
| Parameter | Specification |
|---|---|
| Material | Brass |
| Opening Temperature | 90°C – 99°C |
| Resetting Temperature | ≥ 70°C |
| Pressure Ratings Available | 500 / 600 / 700 / 850 / 1000 / 1200 / 1400 kPa |
| Resetting Pressure | ≥ 85% of rated pressure |
| Standards | ANSI Z21.22 & EN1490 |
Model Variants and Dimensions
| Model | Size | A (mm) | C (mm) | D (mm) | Temp. Steam Rating |
|---|---|---|---|---|---|
| 930008NT | DN15 (1/2″) | Ø37 | 51 | 94 | 15,000 BTU/hr |
| 930003NT | DN20 (3/4″) | Ø37 | 41 | 105 | 105,000 BTU/hr |
Thread options: Rp1/2″, 1/2″ NPT (930008NT); Rp3/4″, 3/4″ NPT (930003NT). Specify thread type and pressure rating when ordering.
Application & Use Cases
- Domestic and commercial water heater protection – The standard and mandatory application for TPR valves in most jurisdictions. Every pressurized storage water heater must be fitted with a TPR valve to provide automatic relief in the event of thermostat failure, heating element runaway, or blocked discharge line
- Boiler safety protection – Installed on hot water boilers to protect against overpressure from thermal expansion, pump failure, or control system malfunction causing the boiler to exceed its design temperature and pressure limits
- Solar hot water storage vessels – Solar collectors can drive storage temperatures to extreme levels during stagnation events when no hot water draw-off occurs. The 930008NT provides essential overheat and overpressure protection for solar thermal storage tanks
- Heat pump hot water systems – Pressurized hot water storage vessels connected to heat pump systems require TPR valve protection as a safety baseline regardless of the heat pump’s own temperature controls
- International projects requiring dual ANSI/EN certification – The simultaneous ANSI Z21.22 and EN1490 certification makes the 930008NT/930003NT appropriate for multinational projects or export products where both North American and European regulatory compliance is required
Installation Notes
- Installation must be carried out by a trained and experienced plumber. Incorrect TPR valve installation is a serious safety hazard — improper installation can prevent the valve from operating during an emergency or cause uncontrolled discharge of boiling water
- Select the correct pressure rating matching the vessel’s maximum allowable working pressure. Never install a TPR valve with a pressure rating higher than the vessel’s rated pressure
- Connect a discharge line to the valve outlet before putting the system into service. The discharge line must direct hot water and steam to a safe disposal point — floor drain, outdoor discharge, or dedicated drain. The discharge line must not be blocked, plugged, or reduced in diameter
- Ensure flow direction matches the arrow marked on the valve body. Reverse installation prevents correct operation
- Flush the discharge line completely before installation to remove debris that could lodge in the valve seat and prevent the valve from sealing after a relief event
- Do not use tapered thread adapters — use standard thread connections matching the valve’s thread specification (Rp or NPT as supplied)
- Conduct a thorough leak check after installation before restoring system pressure
- Annual testing is mandatory: Operate the lever test mechanism at least once per year to confirm the waterways are clear and the valve opens freely. Before testing, confirm the discharge line is connected. If no water flows when the lever is operated, the valve is inoperative — shut off the water heater immediately and call a plumber
- Mineral scale deposits can render the valve inoperative over time. Replace the valve if it fails to open during annual testing or if it weeps continuously after a test
Frequently Asked Questions
What is a TPR valve and why is it mandatory on water heaters?
A Temperature and Pressure Relief (TPR) valve is a safety device that prevents a pressurized water heater or boiler from exploding. If a water heater’s thermostat fails and the heating element continues to operate, water temperature and pressure can rise to catastrophic levels. A sealed, unprotected water heater under these conditions can rupture violently. The TPR valve automatically opens to release hot water and steam before pressure and temperature reach the vessel’s failure point, preventing explosion. Most national building codes and plumbing standards legally require a correctly rated and installed TPR valve on every pressurized hot water storage vessel.
How do I select the correct pressure rating?
The TPR valve pressure rating must match or be lower than the water heater or boiler’s maximum allowable working pressure (MAWP), which is stamped on the vessel’s data plate. Never install a TPR valve with a pressure rating higher than the vessel’s MAWP — the vessel could reach failure pressure before the valve opens. The 930008NT/930003NT is available in seven pressure ratings from 500 kPa to 1400 kPa to match the widest range of domestic and commercial vessels. If uncertain, consult the vessel manufacturer’s documentation.
What is the difference between the 930008NT and 930003NT?
Both valves have identical temperature and pressure performance specifications. The difference is size and heat discharge capacity. The 930008NT is DN15 (1/2″) with a temperature steam rating of 15,000 BTU/hr, suited for residential domestic water heaters. The 930003NT is DN20 (3/4″) with a temperature steam rating of 105,000 BTU/hr, suited for larger commercial storage vessels. Select the size that matches the vessel connection and the BTU/hr rating requirement specified by the vessel manufacturer or local plumbing code.
Why must the TPR valve be tested annually?
Mineral scale from hard water can deposit on the valve seat over time, causing the valve to stick in the closed position. A valve that cannot open during an overpressure or overtemperature event provides no protection. Annual operation of the lever test mechanism verifies the valve opens freely, the waterways are clear, and the discharge line is unobstructed. This annual test is a safety requirement, not optional maintenance.
What standards does the 930008NT/930003NT comply with?
Both models comply with ANSI Z21.22 — the American National Standard for relief valves and automatic gas shutoff devices for hot water supply systems — and EN1490 — the European standard for combined temperature and pressure relief valves. Dual certification confirms the valve meets the performance, discharge capacity, and material requirements of both North American and European regulatory frameworks.
OEM & ODM Customization
Legom supports OEM and ODM services for the 930008NT/930003NT Temperature & Pressure Relief Valve. Pressure ratings, thread specifications, and body configurations 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.
