Removing the water heater!!
 

I've been looking into removing the water heater altogether by trying to store the heat from solar in the ground up to around 140 degrees with four 6" pipes that are about 20' long. Looking into it if you can get the ground to temperature it can hold the heat for upto 6-8 months and the 6" pipe would hold about 122 gallons at 140 degrees Fahrenheit.

The trouble is soil has 4 to 5 times lower thermal capacity (specific heat in english?) than water. You end with basement full of sand to store that heat.

How about to store the heat in melted wax? Its proven.

The set up I'm looking into is actually pretty simple!! You dig down 10' and using the "drill your own well" set up you drill 4 6" pipes into the ground about 2-4 feet apart with a 3/4 pipe going down through the middle. I'm going to see how well it would work in my backyard with a 10' piece of 4" pipe in actually storing heat and get back with you on that!!

https://m.youtube.com/watch?v=xmBDMFyBJgQ