Unless I flunked my physics courses, the pressure in the hot water tank will be the same whether there is an air head or not. Like everything else, water expands when heated. For that matter, so does the air head - it reaches the same temperature as the water in the tank. The air gets compressed, increasing the pressure throughout the tank and back along the cold water inlet.
This does not dispute the notion that back pressure could cause pump failures. However, maintaining a good air head won't alleviate that problem. What it will do is prevent water leakage at the pressure/temperature relief valve.
> Many water pumps that fail has to do with high back flow pressure from the
> hot water heaters. Hot water heaters need to have the top of the tank head
> space of air. If not, the heated water expands from heating and puts high
> pressure back on the cold water input to the tank. That higher pressure goes
> back to the output side of the water pump causing internal failure to the
> water pump parts. A accumulator tank on the output side of the water pump
> will compensate for the back flow pressure. Some folks have recommended a
> back flow valve attached to the input cold water line at the water heater.
> Most water heater manufacturers advise against that. Shurflo's high end pump
> line had high pressure back flow failure problems and the water pumps had to
> be redesigned so that the pump can withstand the higher pressure. All known
> vendor stock was to be replaced as of last August. Camping World now has the
> new designed pumps in stock. You can tell the new design by the pump
> housing. Shurflo warrentee's their high end line for 3 years. Aquahot
> equipped coaches do not have that problem. Chuck B
Gary
--
Gary & Nancy Brinck
2004 American Tradition 40V
2007 GMC Acadia
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