Taco CX300-125 CX Series 79 Gallon Vertical Expansion Diaphragm Tank - CX300-125
The Taco CX300-125 is a vertical expansion tank designed for hydronic heating applications. This tank has a one-inch top connection and a capacity of seventy-nine gallons. It operates efficiently under pressures reaching one hundred twenty-five psi. The diaphragm design ensures permanent separation of air and water, allowing for effective handling of expanding water volumes. The air pre-charge resides in the lower tank volume.
Features
- Diaphragm design allows permanent air and water separation.
- Upper tank volume accommodates water expansion.
- Air pre-charge located in lower section of the tank.
Technical Specifications
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Model: CX
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Series: CX Series
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Height: 53-3/8 inches
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Tank Capacity: 79 Gallons
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Tank Type: Diaphragm
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Application: Hydronic Heating
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Connection Size: 1 inch
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Tank Construction: Steel
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Maximum Pressure: 125 PSI
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Manufacturer: Taco
What our Experts Think
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Engineered for Durability
Built to ASME standards with a rugged steel shell and butyl rubber diaphragm to ensure long-lasting separation of air and water, reducing the risk of corrosion and waterlogging.
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Ideal for Hydronic Systems
With a 79-gallon capacity and 125 PSI pressure rating, it's perfect for commercial or mid-sized institutional heating applications needing reliable thermal expansion management.
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Space-Saving Vertical Design
Vertical configuration allows for easier installation in tight mechanical rooms while maintaining performance and code compliance.
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Low Maintenance, High Reliability
Factory pre-charged and sealed—requires minimal upkeep when properly sized and installed. Non-serviceable diaphragm means fewer failure points over time.
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Smart Value for Performance
Offers a balanced solution between full acceptance and limited acceptance tanks—great choice when moderate expansion volume is expected without overspending.
Q&A
Q: What is the Taco CX300-125?
A: It's a 79-gallon vertical diaphragm expansion tank designed for closed-loop hydronic heating and chilled water systems.
Q: What is the maximum pressure rating?
A: 125 PSI.
Q: What type of diaphragm does it use?
A: It features a heavy-duty butyl rubber diaphragm that permanently separates air and water, preventing air absorption.
Q: What applications is it suitable for?
A: Ideal for commercial and residential hydronic systems requiring air control and thermal expansion management.
Q: How is it installed?
A: Vertically mounted with a 1-inch top system connection.
Maintenance Tips
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Check air pre-charge annually – Shut off system, drain tank, and verify air pressure matches system fill pressure.
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Inspect diaphragm integrity – If water exits the air valve or tank won’t hold pressure, the diaphragm may be compromised.
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Remove air from piping – Bleed system air regularly to prevent pressure imbalance and tank failure.
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Examine tank exterior – Look for rust, leaks, or damage; ensure the tank is properly supported and aligned.
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Test safety controls – Confirm relief valves, gauges, and controls operate within rated pressure (up to 125 psi).
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Monitor temperature – Keep system temperature within manufacturer-recommended limits to avoid stress on components.
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Log maintenance checks – Track pressure readings, issues, and service dates for preventative care.
