Contractors often ask me if the code will allow them to install a water heater in a crawlspace. With recent upgrades to the code, this once common (and mostly unregulated) practice has become rare. When the federal government increased its efficiency requirements for water heaters, manufacturers responded with new designs that effectively phased out gas "lowboy" water heaters; these units, with their low, wide tanks and conventional heat-transfer technology, were not efficient enough.Aside from the shortage of vertical space in most crawlspaces, the most significant challenge for this type of installation is configuring the discharge from the temperature and pressure...

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