Expansion Tank

• Air side up in this mounting - [1]
• Some places say upside down matters - [2]. Supplyhouse says it doesn't matter [3].
• IT seems it does matter - process connection at top, so that trapped air bubbles can float up and out. [4]. If it's on the side, air can get trapped inside. This makes sense to me. Also - can corrode if it's on the side, or put more stress on the bladder [5].
  • Depends on tank. Definitely want to watch the air escape - [6]
• Summary: always think of how the air escapes a pressure or expansion tank. This is for hot water system expansion tanks and RO tanks. But, for water storage (cold) tanks - this one indicates that orientation doesn't matter - could be because the cold storage tanks are built more heavy? Water storage tanks have more air - 2/3 air - [7]. Expansion tanks seem to have 1/2 air.
• RO tank may work as an expansion tank [8]
• Pressure tanks vs expansion tanks [9]

Sourcing

Thermal

• $30 2 gal 3/4" [10]
• $40 Menards 2 gal 3/4" [11]

Reverse Osmosis

• 1/2 gal [12]