Short flushing can occur only in a diaphragm-type
VALVE LEAKAGE AND STICKING
valve. If the disk, diaphragm, and guide have not been
assembled tightly, you may have to reassemble them to
get proper operation. Sometimes you may find that
During normal operation of valves, the use of a
someone has tampered with the bypass tube. It may be
wrench to open or close a valve is prohibited. However,
if a valve is jammed in the open or closed position, a
enlarged so that the water passes so rapidly into the
wrench may be used to unjam the valve. However,
upper chamber that it closes off the valve before the
because of the danger of damaging the valve disk due
desired volume has been delivered. Also, someone may
to overloading of the stem and disk, you should take
have oiled or greased the valve parts. It may have been
extreme care when using a wrench. Where extreme
done to make the valve operate more easily. However,
difficulty is experienced in opening and closing a valve,
the oil or grease ruins the rubber parts and interferes
isolate the valve and disassemble for inspection to
with the action of the valve. You may be called upon to
determine the cause of the problem. Inability to open
correct short flushing in a water closet.
high-pressure steam, flexible wedge, gate valves with
You should first check to see if the correct type of
the normal operating mechanism or handwheel may be
valve has been installed. If a urinal valve has been
an indication of body overpressurization. If the steam
supply to the valve is not shut down immediately, the
installed by mistake, the valve will not be short flushing.
results may be catastrophic.
It is merely delivering the three-fourths gallon of water
for which it is set.
Leakage through the valve is generally caused by
Pressure-reducing valves are installed in branch
the disk and seat failing to make a tight joint, and may
result from conditions described in the following
lines of the firemain to reduce the water pressure to a
paragraphs. Additional information on seating
working level for the flushing system. You will
problems can be found in NSTM, chapter 505.
probably do the maintenance and repair on these
--Foreign Substances. Foreign substances, such as
scale, dirt, waste, or heavy grease may become lodged
The most common problems in these valves are
on the seat so the disk cannot be seated. If obstructing
ruptured diaphragms, binding of the O-ring or cup
material cannot be flushed through, disassemble and
washer, and chattering. A Monel insert is now used to
clean out the valve.
prevent the erosion of the valve body where the O-ring
--Scoring. Scores in the seat or disk are caused by
attempting to close the valve on scale or dirt, or by
A ruptured diaphragm is easily detected, for water
erosion. If damage is slight, the valve may be made tight
from the small hole in the spring chamber casing will
by grinding; if damage is more extensive, reseat the
valve and then grind or replace.
When you have a drop in water volume, check the
--Cocked Disk. The disks may be cocked if the
valve's O-ring or cup washer. If the discharge pressure
feather guides fit too tightly or if the spindle guide or
of a reducing valve becomes greater than the spring
valve stem is bent.
pressure, the volume will drop to almost nothing.
--Damaged Seat or Disk. The valve body or disk
Chattering is more of a nuisance than a real
may be too weak, permitting distortion of the valve seat
problem. It is caused by the fast opening and closing of
or disk under pressure or closing force.
the reducing valve. This occurs when only one or two
--Improper Disk-to-Seat Contact. The disks and
water closets are flushed at the same time and water
seat may not have been machined properly, preventing
supply is greater than demand. Usually most reducing
tight disk-to-seat contact.
valves are designed to handle the larger systems. When
--Extraneous Leakage. Leakage paths may occur
the demand is small, volume is supplied quickly and the
behind inserted seats or threaded seat rings.
valve, in turn, closes quickly. This rapid opening and
closing is what causes the noise. A constant flow in the
--Casting Defects. Casting defects may be present
urinals will probably stop the chattering.
in the valve disk or body, particularly in new valves.