2. Valves – Definition
A Valve is a device that regulates, directs or
controls the flow of a fluid (gases, liquids,
fluidized solids, or slurries) by opening, closing,
or partially obstructing various passageways.
Valves are technically fittings, but are
usually discussed as a separate category. In an
open valve, fluid flows in a direction from higher
pressure to lower pressure. The word is derived
from the Latin valva, the moving part of a door,
in turn from volvere, to turn, roll.
4. Types of Valves
Valves are installed throughout water systems in treatment plants,
pumping stations, and pipe networks, as well as at storage
reservoirs. Their purpose is to control the magnitude or direction
of water flow. To regulate flow, all valves have a movable part that
extends into the pipeline for opening or closing the interior
passage.
The main types of valves are
(i) Sluice Valves, gate valves, stop-cock, bib-tap, shut-off valve,
(ii) Scour valves,
(iii) Pressure relief valves,
(iv) Reflux valve or check valve (non-return valve),
(v) Air Valve or Air-relief valves,
(vi) Flush & mixing valves.
Valves are also commonly classified by operating purpose (for
example, shutoff and altitude) and function (by-pass and flow control)
without regard to the kind of device used.
5. (iii) To control the direction of
fluid flow in pipes.
(iv) To regulate downstream
system or process pressure.
(v) To relieve component or
piping over pressure.
PURPOSE OFVALVES
(i) To stop and start fluid flow in pipe.
(ii) To vary the amount of fluid flow in pipe.
6. GATE VALVES
These are also known as the Gate Valves or Shut-off Valves
or StopValves.
These valves control the flow of water and are helpful in
dividing the water mains into suitable sections. They are
generally placed at a distance of about 150 m to 200 m and
at all junctions. For long straight mains, the sluice valves
can be installed at a distance of about 1 km also to divide the
pipe in different sections. The raising or lowering of valve is
carried out by rotating the handle from top. The installation
of sluice valves is very much useful in case of intermittent
system of supply of water.
The valve consists of a wedge shaped circular disc fitted closely in a
recess against the opening in the valve. This is connected to a wheel
by means of a threaded spindle. The valve can be raised or lowered
by rotating the wheel from the top either manually or mechanically.
8. SCOUR VALVES
These are also known as the blow off valves or
drain valves or washout valves. These are ordinary
sluice valves which are located at dead ends and
depressions or lowest points in mains.
They are operated to
remove sand or silt deposited
in the water pipe. They are
operated with hand and closed
down as soon as clear water is
seen passing through them.
SCOURVALVES
9. PRESSURE RELIEF VALVES
These are also known as the automatic cut-off valves
or safety valves. The load on the spring is adjusted
to the maximum pressure.
The relief valves are located at every point along
the water pipe where pressure is likely to be
maximum.
When pressure of water exceeds a predetermined
limit, the valve operates automatically and it will
save a particular section of water pipe before
bursting of pipe takes place.
11. REFLUX VALVES
These are also known as Reflux, Check Valves or Non-return Valves.
A check valve is a Semi-automatic device which allows water to go in
one direction only.
The reflux valve is invariably
placed in water pipe which
obtains water directly from
pump. When pump fails or
stops, the water will not run back
to the pump and thus the
pumping equipment will be
saved from damage. Similarly at
inter-connections between a
polluted water system and a
potable water system, the
provision of reflux valve will
prevent the entry of polluted
water into the purewater.
SECTION OF CHECK VALVES
13. AIR RELIEF VALVES
These are also ordinarily termed as the Air Valves. Some
quantity of air is contained in the flowing water and this air tries
to accumulate at high points along the water pipe. In order to
provide an exit for such accumulated air, the air valves are
provided at summits along the water pipe. The air valves should
be located at points which are close to or above the hydraulic
gradient. If air valves are not provided, there are chances for
pipes to be air locked. The effective area of flow and
consequently the discharge through water pipe are greatly
reduced due to airlocking.
The provision of air valves along water pipe also helps in
admitting air quickly when vacuum occurs in water pipe due to
sudden breakdown of water pipe at lowpoints.
An air valve consists of a cast iron chamber, float, lever and
poppet valve. The chamber may be rectangular in shape. A
poppet valve is a valve that is lifted bodily.
15. A typical stop cock is shown beside.
The body of the valve is so cast that
the water passes through an orifice
when the valve stem is raised. When
the valve is closed, it rests against
the seat, and thereby closing the
orifice. They are extensively used in
pipes up to sizes of about 50 mm.
Bib tap & stop VALVES
Stop Cocks
These are small sized sluice valves, screw down type and they
are installed in service pipes serving the bib cocks. They operate
on the same principle of sluice valve. They are generally provided
at the water entrance of each building and also within the building.
They are placed on water pipe leading to flushing tanks, wash
basins, water tanks etc.
crutch head
rising spindle
packing gland nut
headgear
jumper body
washer
Packing gland
16. Water Tap:- Tap water is water supplied to a tap. Its
uses include drinking, washing, cooking,
and the flushing of toilets.
Brass, an alloy of copper , steel
and zinc, is the most widely used
material for tap due to its
resistance to soft-water corrosion
and hard-water calcification. It
usually contains some alloying
elements—like bismuth—to make
it easier to process.
Water taps are the types of valves
provided at the end of service
pipes for withdrawing water at the
consumers’ houses. Several
varieties of water taps are
available, and the most common
of them is a “Bib-Tap”.
17. Bib Tap
By rotating the handle of the Bib Cock, the
orifice opening, through which the water
passes, can be increased or decreased, thereby
controlling the outflow through the spout. They
are available to be fitted in different pipe sizes
from 10 to 50 mm dia.
18. Pillar Tap
As per IS: 1795 – 1982 [the Code of Practice on “Pillar Taps for
Water Supply Purposes”], this is a draw-off tap with a vertical
inlet and an uplifted or a horizontal free outlet.
‘O’ ring
washer
backnut
Pillar tap
circlip
non-rising
spindle
19. Pillar Tap
Advantage :- Pillar taps tend to be affordable and easy to install.
Disadvantage :- Two separate taps for hot and cold water.
Uses :- Use in both baths and basins
Quarter turn ceramic disc Pillar Tap
20. SELF-CLOSING VALVE
• Self-closing valve is a draw-off valve which remains in
the open position so long as a lever handle is kept
pressed up, down or sideways, or a push button is kept
pressed in, and closes by itself or when the button or the
lever handle is released. The self-closing valve may
incorporate a device which closes the valve even without
the release of the button or the handle after a fixed
quantity is discharged.
21. A flush valve is a mechanism used to flush a toilet or
urinal. These are fittings which are directly connected to
pressure water pipes. When they are operated, they
allow a limited quantity of water through in order to
flush water closets, urinals etc., and slowly close
automatically.
The valve and associated hardware are located within the
toilet tank or in the body of the urinal. Most toilets have a
lever or push button activator, which is used to operate the
flush valve.
A standard flush valve uses a rubber flapper to hold fresh water within
the toilet tank, though some older models may use a ball rather than a
flapper. As the user flushes the toilet using the lever, a chain connected to
the lever raises the flapper at an angle. When the flapper is raised, the
fresh water from the tank rushes down into the toilet bowl. This forces the
existing water and waste material down through the S-shaped pipe at the
base of the toilet.
FLUSH VALVES
23. mixing VALVES
Mixing Valves or mixer taps have either a single or
two handles on either side of a single spout. Hot and
cold water are mixed in the body of the tap, while
water flow and temperature are controlled by the
individual/separate handles.
Uses:- Usable in bath and basin. Many mixer taps
feature a practical pop-up waste mechanism.
24. Mixing Valves
Hot Supply Cold Supply
Bi Flow Outlet
Bi Flow Outlet
Sections
This type of tap is suitable for unbalanced pressure between
the hot and cold water supply.
25. A single check valve must be fitted to the cold water inlet if the supply
is taken of the main.
This type of mixer tap should only be used when BOTH supplies are at
equal pressure
Cold Supply
Hot Supply
Mixed Outlet
Outlet
in
section
Mixing Valves
