Build a Frame

• 1). Build a frame out of sturdy lumber that will support your water tank and enclose your shower. Building it out of two-by-fours with diagonal crosspieces should be sufficient, or build it out of beams from an old barn if you have them.
  
  
• 2). Make it roughly the size and dimensions of a regular indoor shower stall. Remember that this frame will be supporting up to 20 gallons of water, which are quite heavy, so be sure to make it strong.
  
  
• 3). Sheath the frame with plywood or planks if you want an enclosed shower. Alternatively, you can leave it open, for a more pleasant showering experience and a decreased risk of mold and mildew.
  
  

Install the Water Tank

• 1). Install the water tank on top of the frame by setting it on top of the top crosspieces and screwing down cleats on both sides of it so it doesn't move. The tank can be upright or lying on its side, whichever works better.
  
  
• 2). Paint the water tank black if it is not already black. This will maximize the amount of solar heat that it absorbs.
  
  
• 3). Insulate the bottom of the tank and any parts of it that aren't exposed to the sun, for maximum retention of water heat. Use sheets of rigid foam, which are impervious to getting wet.
  
  

Install the Shower

• 1). Install the hose from the tank to the shower either by inserting the hose into the spout or opening on the tank, or, if there is no opening, cutting an opening at the bottom of the tank just large enough to fit the hose into, and caulking around it to prevent leakage.
  
  
• 2). Secure the shower head to the side of the frame and attach it to the hose.
  
  
• 3). Run the hose that is connected to the tank directly down to the shower head, without any loops. As this system is gravity fed, the water needs to run consistently downward from the tank to the shower head.
  
  
• 4). Fill the tank with water, either by simply climbing a ladder with a bucket, or by installing a pump and hose system. You will need an opening at the top of the tank to do this, in addition to the opening at the bottom to which you connected the hose that runs to the shower head.