SP-8 is an 8-liter (2.0 gallon) expansion vessel designed for closed-loop solar hot water systems. It effectively manages temperature fluctuations to maintain safe pressure levels and protect the system from excessive variations.
Built for extreme environments, the tank supports up to 10 bar (150 psi) and 130°C (266°F). It is factory pre-charged to 3.5 bar (50 psi) with 100% nitrogen gas to ensure stable performance and prevent thermal pressure spikes.
With a compact 20.3 cm diameter, the SP-8 is ideal for point-of-use installations. It supports thermal expansion for water heaters up to 70 gallons, providing a reliable, space-saving solution for solar applications.
Product Overview
The SP-8 is an 8-liter (2.0 gallon) diaphragm expansion tank designed to provide high-level protection for solar thermal systems. It effectively manages the expansion of water-glycol mixtures, ensuring system pressure remains regulated during intense sun exposure and stays stable when temperatures drop below freezing.
Built with a heavy-duty cold-rolled steel shell and a Red (RAL 3011) epoxy powder finish, the tank is highly resistant to oxidation. The interior features a specialized high-temperature liner and a premium EPDM diaphragm (DIN 4807), specifically engineered to withstand the extreme heat and chemical stressors found in solar loops.
The SP-8 includes a 1" 304 stainless steel connector, providing a lead-free and secure connection for residential and commercial solar setups. This CE and ISO 9001 certified vessel offers a durable and professional-grade solution for maintaining the safety and efficiency of modern solar thermal applications.
Certification
Specifications and Technical Data
| Parameter | Value |
| Model Number | SP-8 |
| Total Tank Volume | 8 liters / 2 gallons |
| Diameter | 20.3 cm / 8.0 inch |
| Height | 30.1 cm / 11.9 inch |
| Net Weight (NW) | 1.9 kg / 4.2 lbs. |
| Gross Weight (GW) | 2.3 kg / 5.1 lbs. |
| Shipping Volume | 0.50 CUF |
| Operating Temperature | 1 - 130°C / 34 - 266°F |
| Factory Pre-charge | 3.5 bar | 50 psi |
| Max. Operating Pressure | 10 bar | 150 psi |
| Connection | 1” NPT / BSPT Stainless Steel |
| Liner Material | Polypropylene |
| Diaphragm Material | EPDM Rubber |
| Shell | Cold Rolled Carbon Steel |
| External Coating | Triple Grade Blue Paint |
| Pre-charge Gas | 100% Nitrogen |
Key Features & Design Advantages
How the Solar-Plus Pressure Tank Works
In closed-loop solar systems, the heat transfer fluid (often a water/glycol mix) expands significantly as it absorbs intense heat from solar collectors. The SP-8 manages this by storing the expanded fluid against the high-temperature EPDM rubber diaphragm, pushing against the nitrogen-filled air cushion. This safely relieves pressure. When the system cools—such as at night or in freezing temperatures—the nitrogen cushion forces the fluid back into the pipes, preventing the pressure from dropping dangerously low
Key benefits
Typical Applications
Frequently Asked Question (FAQ)
A: The SP-8 is a 2.0-gallon (8-liter) thermal expansion tank designed specifically for solar hot water systems and evacuated tubes. It is engineered to safely handle thermal liquid expansion for water heaters with a capacity of up to 70 gallons.
A: We use 100% Nitrogen instead of standard compressed air to give you a more reliable and low-maintenance system. Unlike regular air, which fluctuates wildly with temperature changes, Nitrogen stays incredibly stable. This ensures your tank maintains the correct pressure even during the extreme heat of a solar installation, preventing unnecessary stress on your equipment and saving you from frequent service calls
A: Standard expansion tanks are not built to withstand the extreme temperatures generated by solar collectors. The SP-8 features a specialized high-temperature EPDM rubber diaphragm and liner capable of handling fluids up to 130°C (266°F) safely. Additionally, it is designed to manage water/glycol mixtures, which have a much higher coefficient of expansion than plain water.
Customized Colors & Packaging
We offer a wide range of customization options to match your exact needs - from custom colors to branded packaging and logo design.
Watch our video to explore the possibilities and see how we help your products stand out in the market.
Downloads & Certification Links