Tighten the chain mounting bolts until a solid,
watertight connection is formed between the main and
the base of the machine. Check the depth adjustment
on the boring bar, and insert the proper size drill and
tap into the holder. Assemble the machine by inserting
the boring bar through the cylinder and tightening the
cap. Start drilling the hole by applying pressure at the
feed yoke while operating the ratchet handle. After the
drill penetrates the main, the boring bar turns easily
until the tap starts cutting threads. When the tap starts
threading the hole, back off of the feed yoke to prevent
the threads in the main from stripping. Continue to turn
the boring bar until the depth adjustment hits the stop.
You have hit the stop when the ratchet handle tightens
and it can no longer be tightened without undue force.
To remove the tap from the hole, reverse the ratchet
and back the boring bar out by turning it
counterclockwise. When the boring bar is raised high
enough to clear the bottom of the cylinder, close the
flop valve. Check to see that the bypass valve is closed.
This prevents water from entering the cylinder. The
water under pressure from the main is now trapped in
the base of the machine, and the boring bar can be
removed by unscrewing the machine cap. Remove the
drill and tap tool and install a corporation stop of the
proper size in the end of the boring bar. Be sure the
handle of the corporation stop is in the CLOSED
position. Reinstall the boring bar in the cylinder and
tighten the cap. Open the bypass valve to allow the
water-main pressure into the cylinder, so the flop valve
can be opened again. The corporation stop can now be
screwed into the main by turning the boring bar. Since
the corporation stop was closed before being installed,
the only noticeable water leak from the operation is
from the water trapped in the cylinder of the machine.
Release the water pressure from the cylinder by
opening the bypass valve and removing the boring bar.
Disengage the chain from the main and remove the
machine. Check for leakage around the corporation
stop. If the corporation stop leaks, tighten it with an
adjustable jaw wrench.
DISTRIBUTION SYSTEM ELEMENTS
The elements of a distribution system include
distribution mains, arterial mains, storage reservoirs,
and system accessories (including booster stations,
valves, hydrants, main-line meters, service
connections, and backflow preventers).
Distribution mains are the pipelines that make up
the distribution system. Their function is to carry water
from the water source or treatment works to users.
Arterial mains are large-size distribution mains.
They are interconnected with smaller distribution
mains to form a complete gridiron system.
Storage reservoirs are structured to store water.
They may serve to equalize the supply or pressure in
the distribution system.
System accessories include the following:
Booster stations that pump water from storage or
a relatively low-pressure main to the distribution
system, or it may serve a portion of the system that is at a
Valves that serve to control the flow of water in
the distribution system by isolating areas for repair or by
regulating system flow or pressure.
Hydrants that are designed to allow water from
the distribution system to be used for fire-fighting
Main-line meters that serve to record the flow of
water in a part of the distribution system.
Service connections that connect either an
individual building or other plumbing system to the
Backflow preventers that protect the water
source from contamination.
SYSTEM LAYOUT AND SIZE
When distribution systems are carefully planned,
the pipes are usually laid out in a grid or belt system. A
network of large pipes divides the community or base
into areas of several blocks each (fig. 4-36). The streets
within each area are served by smaller pipes connected
to the larger ones. When possible, the network is
planned so the whole pipe system consists of loops,
and no pipes come to a dead end. In this way, water can
flow to any point in the system from two or more
directions; hence, the water supply need not be cut off
for maintenance work or a break in a pipe.
Older water systems frequently were expanded
without planning and developed into a treelike system.
This consists of a single main that decreases in size, as
it leaves the source and progresses through the area
originally served. Smaller pipelines branch off the
main and divide again, much like the trunk and
branches of a tree. A treelike system is not desirable
because the size of the old main limits the expansion
of the system needed to meet increasing demands.
Also, there are many dead ends in the system where