Description
The Watts 0066608 ET-90 XpansionTank is a pre-pressurized, diaphragm-style expansion tank engineered to control thermal expansion in closed-loop potable water and hydronic heating systems. When a backflow preventer or pressure-reducing valve isolates a water heater or boiler from the supply line, pressure can build dangerously as water expands during heating. The ET-90 absorbs that excess volume, protecting pipes, fixtures, valves, and water heaters from damaging overpressure conditions.
With a 3/4″ NPT connection and a 13-gallon total capacity, the ET-90 is well-suited for residential and light commercial applications. Its durable steel shell and FDA-compliant diaphragm ensure long service life and safe use in potable water systems.
Key Features
- 3/4″ NPT connection for easy installation on standard supply lines
- 13-gallon total tank capacity to handle significant thermal expansion loads
- Pre-pressurized diaphragm design separates system water from the air charge
- FDA-compliant diaphragm — safe for potable (drinking) water systems
- Heavy-gauge steel shell for durability and long service life
- Schrader valve allows field adjustment of pre-charge pressure
- Vertical or horizontal installation flexibility
Typical Applications
- Residential and light commercial domestic hot water systems
- Closed-loop hydronic heating systems
- Systems with backflow preventers, PRVs, or check valves that create a closed system
- Water heater thermal expansion control per plumbing code requirements
Why Choose the Watts ET-90?
Watts is a globally recognized leader in flow control and water quality products. The ET-90 XpansionTank line is specifically designed to meet modern plumbing codes that require thermal expansion control in closed water systems. Installing an ET-90 helps prevent nuisance pressure relief valve discharge, extends the life of water heaters and plumbing components, and keeps systems operating safely within design pressure limits.
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