Watts 0556001 Relief Valve

The Watts 0556001 (model 100XL-8-150) is a heavy-duty 3/4 inch T&P relief valve engineered for critical temperature and pressure protection in water heater and storage tank applications. This unit is the direct lead-free successor to the legacy 0066110 model, ensuring compliance with modern potable water standards while maintaining a high discharge capacity of 105,000 BTU/hr. It features a durable lead-free copper alloy body and a thermo-bonded coated thermostat that is specifically designed to resist mineral accumulation and corrosion in harsh water conditions. With a 150 psi pressure setting and a 210°F temperature relief point, this ASME rated and CSA listed valve provides reliable mechanical fail-safe performance. The 8-inch extension thermostat makes it an ideal choice for modern heaters with thicker insulation blankets where standard shanks cannot reach the hottest water in the top of the tank.

• Extended 8-Inch Probe: Specifically designed for water heater safety in units with high-density insulation, ensuring the sensing element accurately monitors the tank's core temperature.
• Dual Protection: Provides simultaneous temperature and pressure relief to prevent catastrophic tank failure, serving as the primary safety component for systems up to 105,000 BTU/hr.
• Corrosion Resistance: Built with a lead-free bronze body and a stainless steel spring to withstand aggressive water chemistry and prevent premature scaling.
• Certified Reliability: Fully compliant with ANSI Z21.22 and ASME Section IV requirements for domestic hot water supply systems.
• Legacy Compatibility: Serves as a drop-in replacement for the Watts 0066110, allowing for seamless retrofitting on older boiler and heater installs.

What causes a T&P valve to drip or weep?
Dripping is often caused by thermal expansion in a closed plumbing system. If the pressure exceeds the 150 psi set point during the heating cycle, the valve will discharge. We recommend installing an expansion tank to manage these pressure spikes.

Is the 0556001 suitable for commercial applications?
This model is ASME rated for systems up to 105,000 BTU capacity. For larger commercial boilers exceeding this heat input, a higher-capacity combination relief valve should be specified based on the equipment's BTU rating.

Why is the 8-inch thermostat necessary?
The 8-inch extension ensures the thermostat is immersed in the top six inches of the tank water, where the temperature is highest. This is critical for preventing "thermal lag" which can delay the valve's response during an overheat condition.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.