Building a water storage tank

Today I'm looking back at the construction of a water storage tank.  It's now all done, and it's interesting to look at how it came together.  This tank is made from manufactured concrete block, using a method which I have several patents on.  I've posted several pictures below showing the construction steps.

This particular tank has an inside diameter of around 7 feet.  It holds around 3,000 gallons.  It is being used as a rainwater harvesting (rwh) tank.  I am using it as a plunging tank to cool off after you take a sauna, which I also built.  The tank has an electric light (LED's) at its bottom center.  There is a ladder which conforms to its spherical inner shape, for easy "in & out."

This tank was easy to build, and should last a very long time.  I hope to be using it to collect rainwater and as part of my wood-fired sauna experience for years to come.  If we assume concrete block cost $1 each, this tank cost me $175, which seems like a pretty good value.  Similar tanks for rainwater harvesting can have many uses: from potable water, to fire suppression systems, to watering crops, etc.  It has a hinged lid to keep insects out and to keep the water clean.  Rainwater is collected from the sauna roof, which is around 1,000 square feet.

I hurt myself (chainsaw accident!) while I was working on this, it took some time to heal.  The actual time to build this entire thing was very short though; less than a week.

The grey plastic pipe was used to run electric wire for the underwater light: thinking ahead.

Some of these mortar joints (especially near the top) are intentionally extra 

thick, this stretches the sphere and makes the water tank deeper. Easily done.

This is the electric light I installed in the bottom center of the tank.  LED's.

The light installed.  It is over 8 feet down to the bottom.

This is the finished tank, with my puppy Bartleby investigating.

Here is the actual sauna room.

 Here's a shower I put in.  The building also has a toilet, sink, bedroom and upstairs deck (outside).

This was a fun project, and I can't wait to use it!