AIR GAP, WATER DISTRIBUTION
• an unobstructed vertical distance through the free
atmosphere between the lowest opening from any pipe or
faucet conveying potable water to the flood-level rim of any
tank, vat or fixture.
• the flow of water or other liquids, mixtures or substances into
the distributing pipes of a potable supply of water from any
source other than from its intended source.
TWO CAUSES OF BACKFLOW
• BACK PRESSURE – occurs due to an increased reversed
pressure above the supply pressure. This may be due to
pumps, boilers, gravity or other sources of pressure.
BACK SIPHONAGE – the flowing back of used, contaminated
or polluted water from a plumbing fixture or vessel into a
water supply pipe due to a negative pressure in such pipe.
a type of pipe connection in which a ball-shaped end held in
a cuplike shell and allows movements in every direction.
BELL OR HUB
• that portion of a pipe which, for a short distance, sufficiently
enlarged to receive the end of another pipe of the same
diameter for the purpose of making a caulked or push-on
• a flange that closes the end of a pipe.
the passage of liquid or gas.
There is no opening for
• any joint obtained by joining of metal parts with alloys which
melt at temperatures higher than 449 degrees centigrade but
lower than the melting temperature of the parts to be joined.
• plugging an opening with oakum, lead or other material that are
pounded into the annular space. Also, the material pounded into
the annular opening.