Fiberglass water storage tube tanks are used for passive solar heating and cooling system Trombe walls. Water tubes prevent temperature swings in greenhouse or sunroom by storing excess solar energy during the day.

Every passive solar storage tube comes complete with a friction fit cap that adds a little over an inch to the final height of the heat storage tube. You can trim the height to custom size with a pair of tinsnips. Full heat storage tubes are heavy enough that gravity keeps them from being 'tipsy', but you are highly encouraged to box them in or strap around the top to prevent an unfortunate accident. These fiberglass solar storage tubes are specially constructed of 23 percent glass reinforcement by weight with no use of fillers or resin extenders. Solar transmission is an average of 85%, with a wall thickness of .040 inches (18 inch diameter tubes are .060 inch). Tube stock meets U.S. Commercial Standard P.S. 53-72. To eliminate unwanted algae growth in solar storage tube water, we suggest adding copper sulfate at the rate recommended by manufacturer (about 1 gram per 250 gallons) and note the chemical is corrosive to metal and hazardous to humans and toxic to fish in concentrated form. Observe all eye and skin safety protection rules. Avoid using bleach or chlorine, as they will dissolve any color dyes you may have in the water.

​Nesting sets of four tubes can ship in one heavy-duty cardboard sonotube 'crate'.
Price posted below is for one tube and one cap, without motor freight and crating fees. 

​12 inch diameter tubes are:  11-3/4", 12-1/8", 12-1/2" and 12-7/8" (nesting set of four tubes)
4 foot tall (~24 gallons)  $169 per tube - includes friction fit cap
8 foot tall (~47 gallons)  $269 per tube - includes friction fit cap

18 inch diameter tubes are:  17-1/4", 17-5/8", 18" and 18-3/8" (nesting set of four tubes) 
5 foot tall (~66 gallons)  $259 per tube - includes friction fit cap
10 foot tall (~132 gallons)  $309 per tube - includes friction fit cap

For a final delivered price quote, please email with quantity and size, your city, state and zip code, and confirm whether drop site is a business or your residence. Please note we do not accept credit card payment for third-party blind drops where the shipping address does not match your MC/VISA billing address. Up to four tubes (one full nesting set) can ship in each crate (wood reinforced cardboard tube). Since freight cost is based upon size, and not weight, we can ship four tubes for the same crating and freight fee as one tube. Only the 12" by 4' tall tubes ship via package service (Fed-Ex or UPS Ground) with all larger tubes shipping via motor freight carrier (in a crate, on a pallet, in a semi-trailer truck). Please note Special Terms and Conditions apply to all buyers of fiberglass water storage tubes.

Here's a close-up of these radiant heat storage tubes acting as a hallway divider.
Prevent temperature swings in sunrooms with fiberglass heat storage tubes for solarium cooling and solar heat storage.

One application is sunroom cooling - water tubes are low tech thermal mass machines with no moving parts. For daytime solarium cooling, water storage tubes prevent wide temperature swings by absorbing and diffusing the sometimes overwhelming solar energy. Then at night, the tubes release stored energy to help keep the attached greenhouse or solarium deck from getting too cold. As space, budget, and design allows, the more tubes the better, when temperature swings fluctuate wildly. Additional thermal mass in a water filled Trombe wall moderates the indoor environment, helping avoid annoying daily temperature spikes and dips. Some people refer to it as 'sunroom radiant cooling' during the day and 'sunroom radiant heating' at night. As a general rule of thumb, subtle, low temperature radiant heat/cooling thermal masses have a noticeable effective range of about ten feet. This makes it a very gentle form of heating and cooling - and certainly silent - which is best for plants and people alike. The radiant energy of tubes will naturally aid the rest of your house, but as a rule, don't factor them too heavily into adjoining room heating/cooling needs.

Blue tinted passive solar heat storage tubes in a trombe wall installation.
Fiberglass passive solar heat water storage tubes in a trombe wall installation

18 inch diameter solar tubes shown above with 3 bottles of blue dye each

Translucent - solar storage tubes diffuse direct sunlight 
Lightweight - 8 foot tubes weigh less than thirty pounds 
Self supporting - installation requires a flat surface 
Corrosion free - strong, durable, fiberglass throughout 
Reliable - no moving parts to break or need repaired 
UV resistant - the factory UV coating can be reapplied 
Easily cut - tin snips can be used to change height 
Color Dyes - black, brown & blue to increase solar gain

Black, brown, and blue color dyes are available to increase solar gain. A single 2 ounce concentrated bottle of liquid dye ($5 each - free shipping with tube order) is enough to color the 12 inch diameter by 4 foot tall tube to a medium dark consistency (2 bottles for larger tubes and 3 for the 18 inch by 10 foot tall). That level of color density will allow some light transmission through, which is the most common installation choice. Add another bottle or two for more opaque coloring of the water. Clients desiring the most solar absorption invariably go with the black, but the blue and brown make for nice alternatives should aesthetics be more of a focus than function. The installation technique recommended is to add liquid dye evenly to surface of tube after it is entirely full (always wear eye protection). Set friction fit cap in place and dye will completely disperse in about an hour. We have MSDS sheets available on the various colors of dye, should you need for the project. 

Solariums and greenhouses with plenty of overhead glass and lots of direct sunlight benefit greatly from solar storage tubes. Tubes are generally placed closer to the windows inside rooms with ceilings and/or vertical glass. Being in direct sunlight is always best for function, but solar storage tubes perform a subtle radiant effect in the shade, too. With an unbroken line of tubes in direct sunlight, you can create a very effective water filled Trombe Wall solar energy storage battery. That analogy of a battery automatically charging, discharging and then recharging again on free solar energy best illustrates heat storage tubes. Rather than view water tubes as a 'heating device', key is knowing how much 'excess solar energy' (Btu's) your home will likely generate. Depending upon design of the home, orientation of glazing, and general construction details, you may have very little or a lot of energy available for the tubes to moderate (absorb) during the daylight hours and release back into the room(s) at night. Fiberglass heat storage water tubes can only absorb as much energy as is directly presented to them. They will absorb some of the ambient temperature differential in the room during the day, but the vast majority is direct passive solar collection from being placed in direct sunlight. If your window area is larger than the area of tubes, the excess solar energy will be primarily collected by the structure itself (surrounding walls and floor). The temperature of tube water will generally moderate to match ambient room temperature by the next morning. When planning for number of tubes and design layout, clients usually base their order on nesting sets of four tubes for best economy since four tubes cost the same shipping and crating fee as one tube sent via motor freight carrier.

Fiberglass water tube specifications for heat storage

HTM Passive Solar eBook - Table of Contents

  1. Introduction to HTM design basics with the following pages going into detail
  2. photo gallery is packed with photos and commentary from our HTM Home Tour DVD video
  3. dry stack surface bonding cement construction photos and sample block layout sketches
  4. floor plans is an annotated progression of layout design choices for more functional HTMs
  5. roof detail chapter outlines T&G plank-style vented roof decking atop log purlin joist beams
  6. sun screens shade panel micro-climate passive cooling design tips and installation tricks
  7. heat storage with fiberglass water tanks providing a means to moderate temperature swings
  8. earth tubing is a simple, passive method for tempering a household's fresh air return intake
  9. solar orientation is important, but HTM designs excel in hot or cold climates alike... anywhere
  10. exterior fascia SBC stucco coatings over EPS foam board insulation and sloped glass details
  11. wing insulation details and shallow footer, frost-protected perimeter foundation treatments
  12. planter beds are central, functional features in greenhouse style HTM home construction
  13. links page is packed full of handy research references and relevant manufacturer websites