Gravel Roof Built-up roof, which is protected from the elements with a final coat of gravel. Stop Raised rim around the edge of a roof, which keeps the final coat of gravel from washing or rolling off. A device used to measure specific gravity, for example liquids. Instrument that measures the gravitation pull of the earth at different places. A return system often used in steam heating which can use one set of pipes with a gravity return condensate system.
Heated water turns to steam and rises through the pipes and into the radiators.
After the steam cools, it condenses into water and drips back, through those same pipes, into the boiler. Gravity Warm Air Heating System Heating system, which circulates warm air through ducting using the rise of warm and the fall of cooler air, to heat a house. Us Copyright 2001 Informedia Group, Inc.