800 Gallon Non-pressurized Solar Hot Water Buffer Tank


The 800 Gallon Commercial Solar Hot Water Storage Tank is a reliable and versatile solution for large domestic hot water preheating and small radiant/space heating applications. Its folded construction allows for easy installation, making it suitable for various locations. With a capacity of 800 gallons and compatibility with up to 4 heat exchangers (purchased separately), this tank provides ample storage and heating capabilities. Made in the USA, it guarantees superior quality and reliability. Experience time and cost savings in your solar hot water installation with this advanced and durable solar hot water storage tank.

SKU: StorMaxx-NP-0800G-6FT Category:

How to order? 

  • Order online or contact sales team directly
  • 24-hour online order confirmation
  • SunMaxx Solar™: solar hot water equipment manufacturer
  • Availability and production lead times subject to production queue

Direct-from-Manufacturer Pricing

Experience the value and benefits of our manufacturer-direct pricing on all online listings. For wholesale and distribution inquiries, we encourage you to reach out to our office to receive a tailored offer that meets your needs.

Looking to connect with our office? Give us a call at 1-877-786-6299, and we'll be happy to assist you!


The 800 Gallon Commercial Solar Hot Water Storage Tank is a high-capacity and versatile solution for large domestic hot water preheating and small radiant/space heating applications. Featuring folded construction and a compact design, this non-pressurized tank can be easily transported through standard 32-inch doors, simplifying the installation process. Measuring 63 inches in diameter and 72 inches in height, this tank offers generous storage capacity. It can accommodate up to 4 heat exchangers, which need to be purchased separately. Made in the USA, this tank ensures superior quality and reliability.


  • Capacity: 800 gallons
  • Dimensions (D x H): 63 inches x 72 inches
  • Maximum Heat Exchangers: 4
  • Heat Exchangers: Sold separately
  • Construction: Folded aluminum
  • Wall Material: EPDM Liner
  • Cover Sheet: Aluminum
  • Insulation Material: Isocyanurate (thickness according to R-Value requirements), 2 – 4 inches
  • Max Temperature: 180 °F
  • Suitable for Installation in Category E
  • Seismic Cleats for installation in seismic zones
  • Production Time: 4-6 weeks

Product Highlights:

  • Versatile solution for large-scale domestic hot water preheating and small radiant/space heating applications
  • Folded construction allows easy transportation through standard doors
  • Generous storage capacity for efficient hot water supply
  • Water fill port at the top of the tank for convenient access
  • Made in the USA for superior quality and reliability

Reduce Time and Costs: The 800 Gallon Commercial Solar Hot Water Storage Tank offers time-saving benefits during installation. Its folded construction and compact design enable easy transportation through standard 32-inch doors, eliminating the need for complex modifications. The tank’s robust construction ensures long-lasting performance, reducing maintenance and replacement costs. Incorporating the latest technology, this tank optimizes energy efficiency and contributes to overall cost savings in solar hot water installations.

StorMaxx™ NP Tank Features

  • Suitable up to 20 collectors ~ 580 ft2 required
  • Max 5 heat exchanger inside the tank
  • Standard sensor ports for all tanks – see in tech. specification
  • Solar & Ice Storage Buffer Tank

  • Perfect for Large DHW Preheating and for small radiant/space heating
  • Foldable design, easy to transport and move through standard 32″ doors
  • Possibility to designate port locations for the manufacture of your tank
  • Water fill port at the top of the tank (1″) included

  • Tanks made in USA
  • Heat exchangers made in USA

StorMaxx™ NP Solar Tanks How to Order

Simple steps on how to order SunMaxx Solar hot water NP tanks. You can order the tanks online or contact us to get a quotation. All only orders are reviewed prior to process for NP tanks, if something is missing, we will contact you to get require pass throughs for piping ports, # of heat exchangers, etc.

  • Select the tanks size you need for your application. If you're not sure what tank size to use for your application, just let us know and we can help size the proper size tank.
  • Determine if you want to use internal heat exchangers or external heat exchangers. For internal, make sure you add these heat exchangers to you order. You can find them below.
  • Determine if you want to have below the water line ports (where your pipe connections come into the tank) or above water line ports. If you are connecting two tanks together in parallel or building a drain back tank with our NP tanks, then we recommend below water ports. For all other internal heat exchangers, we recommend above water ports. The port location and quantity will be reviewed after you order is submitted.
  • Check the dimensions of your door / path to get the tank in its final location. The limiting factor will normally be the height of the tank.

What parts & accessories do I need?

Heat exchangers are not included with a tank. They must be purchased separately. For the assistance please call our sales representative.

The image on right represents three diagrams of an NP tank. You will be writing on the EXTERNAL TANK SURFACE diagram to designate port locations for the manufacture of your tank. Please use the information below to complete the diagram.

Sensor Ports
Sensor ports are standard on all tanks. All 4’ tall tanks get 2 sensor ports, one 2” below the water level, and one 2” above the water base. All tanks taller than 4’ get a third sensor port centered between the other two. Sensor ports are placed near requested piping ports unless otherwise specified.

Piping Ports
You must choose the ports you want installed in the tank and specify their locations. Above water level pass-throughs should be placed on the blue line. Available ports are listed in the chart below. On the EXTERNAL TANK SURFACE diagram, draw a circle where you want each port, and write the letter code from the chart below in the circle designating the port type. If you want your below water level ports at specific heights, write the measurements on the diagram.

Above Water Level Ports
Available PVC Pass-Throughs

CodeDiameter (in)Suitable for:
A13/4" copper
B1-1/41" copper, 3/4" SS flex
C1-1/21-1/4" copper, 1" SS flex
D21-1/2" copper

StorMaxx™ NP Solar Tank Applications

Non-pressure solar storage tanks are an excellent way to store a lot of energy for a low cost. Our tanks outlast most pressurized steel tanks. Find a list of some common applications below.

  • Hotel and restaurants
  • Commercial projects
  • Dairy farms
  • Office buildings
  • Students dormitories
  • Hospitals

Technical Details

Technical details

  • Max Temperature: 180 °F
  • Dimensions: 63in x 72in (D x H)
  • Weight: 281 lbs
  • Construction: Round, 0.032 embossed aluminum
  • Wall Material: EPDM Liner
  • Cover sheet: Aluminum
  • Insulation Material: Rigid R14 isocyanurate foam
  • Tank Sizes: 150 – 5000 gal

For the technical details please see the StorMaxx data sheet in Downloads & Datasheet section.

Technical Features:

  • Suitable for installation in Category E; For engineering calculations, please contact our engineering team for consulting services.
  • Seismic Cleats allow for installation of tanks in seismic zones
  • For HX Sizing: Please contact SunMaxx engineering for proper sizing.
  • Folded construction: tanks fit easily through standard doorways and other openings
  • Both tanks and heat exchangers are made in USA

The technical drawings presented below show placement of pipe pass-through ports, sensors, number of water coil heat exchangers, solar loop heat exchangers and the mounting of the tank to the surface. Please contact our Engineering Department for more information regarding custom designs.

Installing the ports in the bottom parts is not recommended by SunMaxx Solar ™ . They are always installed in the top of the NP tank due to some reason. Firstly the water is filling the tank to determined level. Ports are located above the water surface - no leaking water from tank.  Locating the ports in the bottom parts can cause the leaks and have to be well isolated. Moreover, parts for inslling can cost a huge amount of money. That all issues may lead to some problems,  that SunMaxx Solar ™ install ports on the top locations.
Cleaning the tanks is a process which is simple but easily can cause some troubles. Cleaning the outer layer you can you a pressure washer - it should work. When you want to clean inner site you can also use that device. Before you start remove all the heat exchanger coils carefully, don't cut the rubber membrane. Also the pressure washer can cause some damages in the surface of it, so remember to wash it carefully. After processes place all compactness on their place.
The drain back tank are perfect solution for solar thermal system in the area where climate is challenging.  That means extremely hot or cold temperatures. These tank allows all the water in the system (collector and piping) to drain into the tank reservoir. The water also protects the system form freezing and overheating. Below there is a the simplest scheme of the system with basic components.
The are a lot of different methods how can you check the water level and measure it. The simplest method is to use the wooden stick (length is greater than tank height) or line ended with some heavy weight. After that you can measure the level with measuring tape. For sure you can find some sophisticated methods but using simple one you will reduce amount of money spend on a special equipment.How can you do it in a 5 simple steps:
  1. Remove the top lid of the NP tank.
  2. Take a stick or line and put it to the tank (in both situations this items should touch the bottom lid).
  3. Mark a level of water and take out stick or line.
  4. Measure the distance with a measuring tape - you will instantly know the level of water in your tank.
  5. Put the top lid on the NP tank to close it.
The amount of heat exchangers which can be fit in the tank mainly depends on the size of the NP tank and its increasing with the diameter of the tank. Before you buy the heat exchanger please check two parameters:
  • The height of the NP tank - heat exchangers can't be higher that tank
  • Maximum amount of HX which can be fit in the tank
All the information which you need are located in the table for every tank or in datasheet (LINK). 

Connecting the heat exchanges depends on a customer requirements. The number of HX depends on some factors like tanks size, number of collectors and heat requirements. There are some possibilities to connect the heat exchangers. In our offer 80/80 Stacked 3/4" Corrugated Stainless Steel HX and 90 3/4" Corrugated Stainless Steel HX. Customer can connect HX in few ways. Only Solar Side, no connection in DHW side or both side connected.

DHW&Solar Side Connection - Stacked HX


Connection used in stacked HX. One of the most common type of HX connection. Requires some additional elements like HX Connection Tees. Applicable for connection HX on DHW side and Solar Side. For more accurate questions you can contact the engineering team.

Solar Side Connection - Stacked HX


Connection used in stacked HX. Requires some additional elements like HX Connection Tees. The connection type uses only the Solar Side ports. There is no heat exchanger connected with DHW Side.

DHW&SolarSide Connection - HX


Connection used in single HX. Requires some additional elements like HX Connection Coupling. Applicable for connection HX on DHW side and Solar Side.  One heat exchanger is connected to solar loop, there other is connected to DHW loop. There is a possibility to add more heat exchangers on both side. In this case you will need some extra elements like HX Connection Tees.

SolarSide Connection - HX


Connection used in single HX. Requires some additional elements like HX Connection Tees. The connection type uses only the Solar Side ports. There is no heat exchanger connected with DHW Side.

Sunmaxx Solar tanks are typically used to pre-heat to an existing primary tank. This solutions has some advantages and its definitely more effective than installation the integrated heat source inside the solar tank. Pre-heating help to reduce the heat loses and price of electricity bills. The main factor of this solution is efficiency .
Yes you can. But we are recommending to use dedicated parts to our installations. All products can be easily connected using the SunMaxx Solar products. Moreover they we designed to different type of connections. Changing the parts and system installation may led to some problems or improper way of working the system.  If it is not enough for you , call us we will help you.


  • 7 years limited on tank and coil heat exchanger
  • 3 years limited on tank and coil heat exchanger in all commercial installations

Why SunMaxx Solar

Investing in a complete solar hot water kit from a single manufacturer is essential for ensuring the longevity and efficiency of your solar hot water system. A streamlined approach to sourcing components simplifies the process of installation, maintenance, and servicing.

By choosing a single manufacturer for your solar hot water kit, you can benefit from comprehensive documentation for service and maintenance. This approach helps prevent issues arising from improperly installed or maintained systems. Studies show that over 60% of solar hot water systems fail due to incorrect installation or lack of proper maintenance.

Purchasing a complete kit from one manufacturer guarantees compatibility between components and streamlined support from the provider. This ensures that you have access to knowledgeable experts who can address any concerns or questions related to your specific system. Furthermore, a single manufacturer can provide a unified warranty, eliminating the need to deal with multiple companies in case of any issues.

In summary, investing in a complete solar hot water kit from a single manufacturer is a wise decision for homeowners and businesses alike. It ensures smooth installation, proper maintenance, and reliable long-term performance, maximizing the return on your investment and providing a sustainable hot water solution.