In {TAIL ~ a preferred installation} for the preheating of water to a hot water heater, {HEAD ~ the inlet second fluid} will comprise cold tap water at line pressure and the thermosiphon loop of circulating heat transport liquid will normally be maintained at a positive static pressure of less than 10 psig  
In { TAIL ~ a preferred installation } for the preheating of water to a hot water heater , { HEAD ~ the inlet second fluid } will comprise cold tap water at line pressure and the thermosiphon loop of circulating heat transport liquid will normally be maintained at a positive static pressure of less than 10 psig
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