16 Gallon Solar High Temperature Expansion Tank

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Introducing the Solar Hot Water Expansion Tank: Designed for solar heating systems, it offers a 16-gallon capacity, high-pressure rating, and a 3/4″ NPT connection. Enjoy reliable hot water, durability, and peace of mind with the included 5-year warranty. Upgrade your system for optimal efficiency and performance.

SKU: XMaxx-EXP-HT-16G-3/4IN Category:


Product Description

Great for larger solar hot water systems, the XMaxx 16G expansion tank from SunMaxx features a rugged carbon steel body, replaceable inner membrane, stainless steel flange and a 3/4″ connection.  Capable of supporting system temperatures up to 210F and pressures up to 87 PSI, the 16G expansion tank is a powerful, critical component to your SunMaxx solar hot water system.

Before you buy

Buying this product you will only purchase the 16G expansion tank.  Connections, fittings and mounting accessories have to be bought separately. Check the list below, before you want to buy 16 G expansion tank.

What parts & accessories do I need?

Fittings for expansion tank. Easy to stock in your tech-van, less parts to inventory.
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Technical Details


  • Volume: 16G
  • Max Accept Volume: 8G
  • Max Operating Temperature: 265°F
  • Max Working Pressure: 145
  • Factory Pre-Charge: 36psi
  • Height: 26in
  • Diameter: 15in
  • System Connection: 3/4 in
  • Shipping Weight: 29 lbs
  • Shell Material: Carbon Steel
  • Diaphragm Material: Rubber
  • Liner Material: Membrane Vessel
  • Fluid Type: Glycol / Non Potable Water


1. **Volume: 16G** – This is the total volume of the tank, expressed in gallons.

2. **Max Accept Volume: 8G** – This is the maximum amount of fluid the tank can accommodate due to thermal expansion, often termed the acceptance volume. It’s half of the total volume, meaning the acceptance factor is 0.5.

3. **Max Operating Temperature: 265°F** – This is the highest temperature the expansion tank can safely withstand during operation.

4. **Max Working Pressure: 145** – This is the maximum pressure (likely in psi) that the expansion tank is designed to handle.

5. **Factory Pre-Charge: 36psi** – This is the air pressure with which the tank comes pre-charged from the factory. This pressure should typically match or slightly exceed the cold, static pressure of the solar fluid in the system.

6. **Height: 26in** – This is the height of the tank, measured in inches.

7. **Diameter: 15in** – This is the diameter of the tank, measured in inches.

8. **System Connection: 3/4 in** – This is the size of the inlet/outlet connections on the tank. A 3/4 inch connection is standard for many residential systems.

9. **Shipping Weight: 29 lbs** – This is the weight of the tank when it’s shipped, which includes the tank and any packaging.

10. **Shell Material: Carbon Steel** – This refers to the material the outer shell of the tank is made from. In this case, it’s carbon steel.

11. **Diaphragm Material: Rubber** – The diaphragm is a flexible membrane that separates the fluid in the tank from the compressed air. In this case, it’s made of rubber.

12. **Liner Material: Membrane Vessel** – This suggests the internal surface of the tank (which comes into contact with the fluid) is a membrane vessel. This could imply that it’s a type of bladder or diaphragm tank, designed to keep the fluid and air separate.

13. **Fluid Type: Glycol / Non Potable Water** – This is the type of fluid the tank is designed to work with. In this case, it’s a glycol solution or non-potable water, which is common in solar thermal systems.

SunMaxx’s Pump Stations are an all in one solar hot water component featuring a circulator pump, a digital controller and valves engineered to keep your system circulating the solar heat transfer fluid through the collectors and into the storage tank.

SunMaxx will size a pump station specific to your needs. No need to do the math!!!

Our pump station’s fill valve has GHT hose threads on the outside. You can easily make an adaptor using the following three fittings, which can be purchased at your local hardware store or plumbing supply.

  • Schrader valve x ¼” male NPT
  • Reducing Bushing, ½” NPT Male x ¼” NPT Female
  • Hose fitting, ½” NPT male x ¾” swivel GHT female

Use Teflon tape on the NPT threads of the Schrader valve and bushing in constructing the adaptor. When attaching the adaptor to the pump station, be sure to use two tools: one to hold the fill valve in place, and one to tighten the adaptor. That way, you won’t create leaks in the pump station itself while testing.

Take a deep breath and let all your air out… of your Solar thermal system One of the biggest issues with a successful commissioning is air removal. Any time you spend with this detail will be time well spent. Air pockets become entrained within your HTF and like to find places to hide. Air pockets can form between your HTF and the inner wall of piping (especially with flexible piping) and can only be removed through persistence and time. Here are a few things you can do to help this process. First, be sure that your air purger is located on the high and hot side of your collector series. The hotter the fluid the less the ability for dissolved gasses to stay in solution and the higher the air vent, the more likely you will effectively remove trapped air that, due to its buoyancy, will rise to the top. Once you feel most of the air has been removed this way, you can shut that air eliminator off or remove it all together. If you install a Titan Power Plus collector, you will have a manual air bleeder permanently installed in your line set connections. If you install a ThermoPower collector, you will include an air vent that should be isolated and de-commissioned at this point. Now, down to the pump station. The UniMaxx pump stations have an integral air eliminator with a scoop that will allow entrained air to collect and be bled off manually by opening the valve up to a full turn until HTF comes out. This can be done each day for the first few days or periodically checked. Smaller systems will take much less time removing the air. Another way of enabling the removal of air is to run the pump at maximum speed during commissioning, this will help to break the friction that holds the bubbles to the inner wall thus forcing the bubble through and out. After words, you should adjust your pump speed accordingly. If air persists in your system, it will inevitably find its way to the suction side of your pump and cause cavitation and eventual pump failure. If your pump appears to be not pumping, it is likely that although it is receiving 115v, it cannot pump because of air pockets. Simply unplug your pump and manual override and give it a few minutes. Air will work its way out, pump can run and then you need to go back to the air purging steps. Please view our SunMaxx technical manual (linked) for further instruction in effective system commissioning.

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How to Order:

If you are confident with your solar hot water heating requirements you can place your order online by clicking on the add to cart button which is located above. All orders are reviewed by our solar hot water heating department and the customers are contacted in order to ensure that you have ordered the correct merchandise for your application. In the event you have any questions our sales staff are available from 8:30AM to 5:30PM EST.

Silicon Solar Inc ships products internationally please ask your sales representative for a shipping rate to your destination.

Need Assistance?
If you have questions need help or simply feel uncomfortable placing your order online feel free to contact the product representative at 1-800-786-0329.