Cylindrical potable water expansion vessel
The vessel is supplied pre-charged with nitrogen. Before commissioning, the installer checks the pre-charge and adjusts it to the cold water supply pressure while the vessel is still empty. The supply pressure must stay within the 10 bar maximum operating pressure, so a pressure-reducing valve is fitted where the mains pressure can exceed it.
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Description and application
The THERMALINO cylindrical potable water expansion vessel takes up the thermal expansion of heated drinking water in closed hot water systems, keeping pressure stable and protecting the water heater, pipework and fittings. Used as an expansion vessel for water heaters and hot water cylinders, it has a replaceable EPDM membrane, is supplied pre-charged with nitrogen, is rated for a maximum operating pressure of 10 bar and conforms to EN 13831.
The cylindrical potable water expansion vessel from the THERMALINO Eternal line is a closed, membrane-type vessel for drinking water systems. When water is heated in a closed system, its volume increases and has nowhere to go. The vessel takes this extra volume against a nitrogen cushion and returns it to the system as the water cools, keeping pressure steady and reducing unnecessary discharge from the relief valve. It conforms to EN 13831 and is rated for a maximum operating pressure of 10 bar. Water is held inside a replaceable EPDM membrane of Italian origin, so the membrane can be changed during service instead of replacing the whole vessel. It is shipped pre-charged with nitrogen and finished in blue. It is available in 2, 5, 8, 12, 18, 24, 35 and 50 L sizes. Besides the standard connection, it can be supplied with other connection sizes on request. The vessel is used on water heaters and hot water cylinders in homes, apartment buildings and commercial premises. It is also used on cold water booster sets and pressurised drinking water lines. It is designed for wall mounting and is connected to the cold water supply of the heater, downstream of the pressure-reducing and non-return valves. Before filling, a qualified installer adjusts the pre-charge to the cold supply pressure. Dimensions, connection sizes and temperature limits for each size are in the technical data sheet.
- Water heaters and hot water cylinders in closed domestic hot water systems
- Houses and apartment buildings
- Hotels, hospitals, schools and sports facilities
- Offices, shops and other commercial buildings
- Cold water booster sets and pressurised drinking water lines
- Solar and heat pump hot water storage, subject to the temperature limits in the technical data sheet
- Drinking water supply in industrial and agricultural buildings, within the 10 bar maximum operating pressure
Technical summary
- SKU
- THL-E-EXV-0002
- Origin
- Made in Türkiye
- Size range
- 2 L – 50 L
- Application
- Potable water
- Membrane
- EPDM
- Membrane type
- Replaceable
- Max. operating pressure
- 10 bar
- Mounting
- Wall
- Standard
- EN 13831
Questions
- What is a potable water expansion vessel, and how is it different from the expansion vessel used on a central heating boiler?
- A potable water expansion vessel, also called a potable water expansion tank, absorbs the expansion of heated drinking water, and its membrane is made to be in contact with drinking water. Heating vessels are built for closed heating water and are not intended for drinking water. The THERMALINO cylindrical vessel conforms to EN 13831 and holds the water inside a replaceable EPDM membrane, so water does not touch the inside of the steel shell.
- How do I size a potable water expansion vessel for a 50 gallon hot water heater in a family house?
- A potable water expansion vessel for a water heater is sized from the heater's stored volume, the cold supply pressure, the relief valve setting and the maximum stored water temperature, not from the heater volume alone. Because the supply pressure and temperature change the result, two heaters of the same size can need different vessels. The THERMALINO vessel is available in 2, 5, 8, 12, 18, 24, 35 and 50 L sizes, and our team can help choose the size if you send these values with your enquiry.
- Where should a potable water expansion vessel be installed on a water heater with a pressure-reducing valve and non-return valve?
- A potable water expansion vessel is installed on the cold water supply to the water heater, between the non-return valve and the heater, so that the expanded water can reach it. The THERMALINO vessel is wall-mounted. Before filling, its nitrogen pre-charge is adjusted to the cold supply pressure set by the pressure-reducing valve, which must stay within the 10 bar maximum operating pressure. The installation is carried out by a qualified installer according to local regulations.
- Do I really need an expansion vessel on an unvented water heater when the cold mains has a non-return valve fitted?
- An unvented water heater with a non-return valve on the cold supply needs an expansion vessel, because the heated water can no longer expand back into the mains. Without a vessel, pressure rises each time the water heats. The relief valve then drips or discharges, and the heater, pipework and taps are under extra stress. A correctly sized and pre-charged potable water expansion vessel takes up this volume and keeps the pressure stable.
- How can I tell if the expansion vessel on my water heater has gone bad or become waterlogged?
- An expansion vessel on a water heater has usually failed when the relief valve drips repeatedly, water pressure at the taps rises after heating, or the vessel sounds solid and feels heavy because it is full of water. Common causes are a lost pre-charge or a damaged membrane. Water appearing at the air valve points to a damaged membrane. On the THERMALINO vessel the EPDM membrane is replaceable, so a qualified installer can check the pre-charge and, if needed, change the membrane.
- Can a homeowner replace the expansion vessel on a water heater, or should a plumber do the work?
- Replacing the expansion vessel on a water heater should be done by a qualified installer, because the system is under pressure and holds hot water. The work involves isolating and depressurising the system, setting the pre-charge to the supply pressure and checking the safety valves. If you notice signs of failure, such as a dripping relief valve or changing water pressure, ask an installer to inspect the vessel.
Range
| Size | Blue | Variant codes |
|---|---|---|
| 2 L✓ Blue | ✓ | |
| 5 L✓ Blue | ✓ | |
| 8 L✓ Blue | ✓ | |
| 12 L✓ Blue | ✓ | |
| 18 L✓ Blue | ✓ | |
| 24 L✓ Blue | ✓ | |
| 35 L✓ Blue | ✓ | |
| 50 L✓ Blue | ✓ |
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This product is listed under Potable and Sanitary Expansion Vessels.
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