Download Construction Document Notes

Mechanical Plumbing Systems
Supply water systems supply clean water, the system is under pressure, thus is must be
sealed. Sanitary waste systems remove contaminated water and generally are not under
pressure, they drain by gravity. Storm drains are similar, drain by gravity and the pipe sizes are
generally larger.
SUPPLY
It must be clean and potable. Several contaminants may cause problems, they must be
considered.
ACIDITY is measured in PH from 1-14, which represents a basic or alkaline solution. Neutral
water has a ph of 7, the greater the acidity the lower the ph. Acidity of the water causes
corrosion problems in the piping.
HARDNESS is caused by minerals in the water like, limestone, calcium and magnesium. Hard
water causes deposition on the piping and is particularly a problematic in heat exchangers. A
piece of metal sometimes is inserted in the hot water tank, this is called an anode. Hardness
also interferes with the cleaning capacity of detergents. Water can be softened by removing
the mineral ions. This is done using the zeolite or ion exchange process.
CARCINOGENS are agents like CB’s & DDT. They are found in the ground water.
BACTERIAS, which comes from the improper disposal of human and animal waste.
The traditional; treatment for public water consists of settling out contaminants, and letting
sediment settle out. Chlorine may be added to kill bacteria’s. Fluorine sometimes also. if the
oxygen level is low the water is passed through a spray or waterfall.
MATERIALS
STEEL originally was untreated and called black because of its color, it has been replaced by
galvanized steel. Schedule 40 is the most common. Joints are joined by threaded connections.
When used in drainage systems the two ends are often clamped together with a rubber sleeve,
a steel jacket and two steel band clamps.
COPPER is often used for supply piping, and is considered to be the best material for that
purpose. Copper doesn’t rust. There are 3 categories: type K, type L and type M(the most
common). Pipes are joined by a form called soldering called sweating. The advantage is that
the system is reversible, by reheating the joint the pipes can be slid apart.
PLASTIC is the prime competitor of copper. There are 2 types PVC, which are used for supply
piping-white with light blue letters- and ABS which is typically used for drainage-larger, black &
white letters. Plastic doesn’t corrode but it deteriorates when exposed to ultraviolet lights. It
should never be exposed . the connections are basically the same as copper, but they cannot
be restored.
Four types are used for cold water; PE polyethylene, ABS, PVC & PVDC( which is suitable for
hot water.
WATER PRESSURE
Water is heavy and requires a great deal of pressure to lift it. The pressure of 1 PSI can lift a
column of 2.3 ft. in other words also 0.433 psi can lift 1ft of water.
PSI pressure per square inch
STATIC HEAD is the pressure required to push water vertically, or the inches or feet of water
that can be supported by a given pressure
If we are asked to determine the pressure at the base of the building, we must know the
pressure req by the fixture, the amount of stories the bldg has and the height of the stories. So
for example: 10 story bldg, 12 ft each story, the toilette reqs. 15 psi.
10x12=120 ft
120 / 2.3 ft= 52.2 psi
remember 2.3 ft can be lifted by 1 psi
52.2 + 15= 67.2 psi this is the pressure you need at the base, we add 15 because that is the
pressure that the fixture requires.
High-pressure causes wear on washers and valve seats. When the pressure passes 80 psi a
pressure regulator should be installed which keeps the pressure btwn 40-60psi.
There are 2 primary ways to supply water, the upfeed or downfeed system, the choice btwn
the two is usually based on the height of the bldg and pressure req to operate the fixtures.
The practical limit for bldg heights in an upfeed system is 40 to 60 ft.
The height of the zone served by a downfeed system is determined by the maximum allowable
pressure on the fixtures at the bottom of the zone. This max pressure usually is 45-60 psi. we
must also consider the minimum pressure for the fixtures to work, this is for the top fixtures,
then we can determine the height of the storage tank.
If the pressure is not enough to supply, other systems must be employed to add more
pressure, which are:
DOWNFEED SYSTEM, consists of a tank at the roof, which supplies the upper floors. A pump
sends water to the roof tank.
PNEUMATIC TANK SYSTEM uses a pressurized tank in the basement to supply higher floors.
Some air is left in the tank, which when it’s compressed acts like a spring on the water. The
down side is that it takes up space in the basement for the tank.
TANKLESS SYSTEM requires one or more pumps that function constantly at different
speeds.
FRICTION
We must consider the flow rate and the resulting pressure losses due to friction. The friction
loss is a function of the diameter of the pipe and the flow rate itself. Valves, tanks, meters, and
other devices add friction. We must determine the amount of friction loss to determine all the
pressure req. at the base of a building. The smaller the pipe the greater the friction
We must determine the total pressure loss when sizing a system. We need to add all the
values
Pressure at the most remote fixture --------- value by table
Pressure loss from static head-which is found by multiplying the total height by 0.434
Pressure loss by friction on piping-trial & error
Pressure loss through water meter
All these values must add and be less than the main line pressure
The probable demand flow is found by determining the demand load of the entire system or
individual parts of the system. Probable demand is defined by FIXTURE UNITS (FU). A fixture
unit is a unit flow rate of approximately equal to 1cuft per minute. We need to determine the
demand flow to size the piping.
In pipe sizing we:
1. Determine the FU of all the fixtures in the system. We list the fixtures and go to a table
that will give us the FU of each fixture
2. With the FU we go to a table to determine the flow rate that we have. This will give us a
value in gpm. We have to be careful if the fixtures are with flush valves or flush tanks.
3. With this value we’ll use a chart that has the flow rate(gpm), the velocity of the water
and the pipe size. We determine our pipe size
The velocity of the water flow is important because of the noise it can cause. 10ft per second is
too noisey, anything over 6ft per second is considered noisy.
HOT WATER SYSTEMS
Water heaters, they are always pressurized and rated in terms of it’s volume(capacity in
gallons) and recharge rate(length of time to reheat after the water is emptied)
There are two basic heating methods direct and indirect. Direct the water is in contact with the
heated surface, Indirect uses an intermediary transfer medium to heat the water. There are 3
basic equipment types regardless of the system:
Continuous loop system(circulating), pumps hot water continuously in the system, the user
doesn’t have to wait for the hot water.
Storage tank
Tankless, like the electric instantaneous.
All hot water pipes must be insulated to conserve the energy.
A totally different approach is the in-flow or instantaneous heater. The system is activated only
when the hot water faucet is turned on. They can consist of electric resistance coils or small
gas burners.
Common temperatures are: 105o for hand washing, 140o for dishwashing and laundry. Water
above 110o becomes uncomfortable to touch
THERMAL EXPANSION must be considered in hot water pipes. This affects the length of the
pipe. The formula that expresses the change in length is:
AL= Lk (T2- T1)
AL-the change in length
L- Length
k-coefficient of expansion
T2-final temperature
T1-original temperature
Each material has a coefficient of expansion. This movement might present problems, this is
why pipe supports on long runs must be flexible, especially in hot water pipes.
Plastic pipes should be supported every 4 ft
Copper pipes every 6 ft
Steel pipes every 12 ft.
VALVES
Valves are used to control water flow. They are located at risers, horizontal branch lines, and
pipe connections to fixtures and equipments.
GATE VALVE is intended to be entirely on or off
GLOBE VALVE is used not only to turn water on and off but also to meter water. They restrict
the flow rate even when they are entirely opened. The friction loss in these valves is big, due to
the fact that the water needs to make the 90o turn.
CHECK VALVE, WHICH ESSENTIALLY IS A backflow preventer. It prevents water from
moving backwards through the system, critical in avoiding contamination of the community
supply system.
PRESSURE RELEASE`VALVE is a safety device which keeps the system from exploding by
opening when the pressure exceeds some preset max. they are req. in water heaters.
SURGE ARRESTORS are devise to deal with the water hammer, which is that sound that
occurs when a faucet is shut off rapidly. This occurs upstream of the fixture where there is a
long run.
In order to determine the pipe size an arbitrary unit is used that takes in account that all the
fixtures will be in use at the same time. This is called the FIXTURE UNIT-FU. Two tables are
used to determine the pipe size, the FU per fixture type and the pipe sizes for total FU’s.
WASTE SYSTEMS
Sanitary waste is kept separate from storm water systems.
SANITARY SYSTEM
Is assumed to be contaminated, because sometimes it is. There are 2 categories of sanitary
lines; soil lines & waste lines.
SOIL LINES (grey water)carry water from toilettes, urinals, showers, sinks and similar fixtures.
WASTE LINES(black water) carry all other wastewater from inside the bldg.
To relieve the pressure and break up the siphoning that occurs, sanitary systems are
connected to vents which rise out of the building to the open air. There are 3 types of venting:
SOIL STACK is a large pipe that has all the waste and soil lines connected to, it is opened at
the top to the open air.
VENT STACK is a smaller pipe that is the air intake line for all the fixtures and also separately
opened to the outside air.
STACK VENT vents the soil stack, and is the portion of pipe that’s above the last fixture
Minimum diam. For vents is 1 ¼”
Cast iron pipe is most often used for sanitary lines
Copper or galvanized steel for vents
Plastic sometimes in residential applications
SOIL LINES(BLACK WATER)- drain urinals and toilettes
GREY WATER drains sinks and showers
Every sanitary clogs up, there are fittings that deal with this:
INTERCEPTERS are designed to catch grease, hair, money, and objects in general. They are
provided with some means of clean out so the trapped material can be removed, it also has a
trap to keep the gases from backing into the building.
TRAP under the sink, shower, etc. always with water, this is to prevent the gases from the
sewer from passing back into the building.
CLEAN OUT is a Y shape segment of the pipe, which serves an area that would be otherwise
difficult to access. They should be placed every 50ft in pipes 4” and every 100ft in larger pipes.
There should be a clean out at every change in direction of the pipe system.
MANHOLES are like cleanouts for larger lines. They should be placed every 150ft.
SEWAGE TREATMENT SYSTEMS
PUBLIC SYSTEMS, all the sewage is treated in a main plant.
CESSPOOL is an underground chamber with porous bottom and walls. The sewage soaks into
the ground. In some communities it is outlawed by code
SEPTIC TANK AND LEACH FIELDS is the combination of a tank where sewage collects. The
solid material deposits and the liquid waste passes to the leach field. The septic tank must be
cleaned over time; they are sized based on the flow of 100 gal per day per person. The leach
field is a ceramic pipe laid underground with perforations so the liquid can leak out. It is
installed over a bed of gravel, which filters the wastewater.
GROUND WATER RECHARGE
Many suburban areas have large depressed areas that flood during heavy drains, the water
later soaks into the ground. This drainage is done by using swales and catch basins.
SWALES are shallow; V shaped sloping channels that take the surface runoff where it’s
collected.
CATCH BASINS are similar to manholes, they have a grated cover, they are placed in the
lower parts of a depression, parking lot, etc. to collect runoff water and pass it to the storm
drainage system.
PRIVATE WATER SUPPLIES include WELLS. Wells are drilled or bored. The depth varies, a
well less than 25ft is a shallow well. The yield is the number of gallons per minute it provides; if
the yield is low a storage tank is provided. Several kinds of pumps are used in wells.
SUCTION pumps are suitable for less than 25ft
DEEP WELL JET PUMPS operate on depths from 25 – 100 ft; the pump & motor are above
ground
TURBINE pumps are use for high capacity systems with deep wells
SUBMERSIBLE pumps are the most common for residential & small bldgs. The pump is under
the water table.
Wells systems also require storage or pressure tanks
DRAINS & GUTTERS
The sizing of drains, gutters and leaders is based on the area of the roof or paved area to be
drained and the annual rainfall. The slop is also a factor in horizontal piping, the lower the
slope the greater the pipe size.
Tables are given in codes to determine the gutter size. The information you need is the
projected sq.ft. of the roof, the annual rainfall and the gutter slope.

One of the first things that an architect must do is locate where the main water line is, its
size, pressure and cost for tapping the line.

The process by which water constantly circulates in the earth is called the hydrologic
cycle

The designer determines the plumbing facilities needed for a project by consulting the
international plumbing code or other applicable codes

For roughing the sizing storage capacity of cisterns we use the monthly average rainfall,
monthly water usage and the catchment area yield.

In a typical cistern system a roof washer gets the dirtiest first runoff from the roof. It
filters the rainfall, usually next to the main leader

By using porous pavement more storm water can be retained on site. This is what we
want to achieve, the water will drain through the porous pavement.

Gutterless sloped roofs with gravel filled trenches skirting the building perimeter is one
site design approach for rainwater recharging

Recharge basins are used in developments where there are no storm sewers to deliver
storm water to the ground.

The size of gutters and leaders depend on the horizontal projected area of a roof and
the design rainfall rate

Routing storm water inside a building can be a problem because of sweaty pipes,
condensation the rainwater is cold..inside warm. Like a glass of ice water.

When rainfall contacts surfaces foreign substances contaminate the water.

The water treatment process begins with filtration

Distillation is the process that water is evaporated so pollutants are left behind.

When sizing hot water systems for commercial and institutional buildings it is important
to consider the trade off between recovery time and storage capacity

Direct passive solar water heating system uses only water to be heated, only one fluid,
the water.

A conventional water closet uses 3.5 gal to flush

A water saver water closet uses 1.7-3.5 gal to flush

A dishwasher uses 1-18 gal per cycle

A washing machine uses 40-55 gal for a full sized load

The hydro pneumatic method of distribution of water through out a building uses pumps
to force water into sealed tanks, compressing the air within.

Drip irrigation is a water conserving irrigation approach that uses emitters to slowly and
steadily supply water onto the ground surface at each plant.

The average US residential usage is 140 g/day of potable water. With attention to
recycling the potable water usage can be cut by 25%

In residential design, when designing a layout and sizing the piping system for sanitary
drainage, the first step is to identify where the fixtures are located

The greater the horizontal distance from the core the more vertical clearance that will be
needed to allow the drain to slope. This is important to keep in mind in multistory
buildings

Aerobic treatment units depend upon air bubbled through the sewage to achieve
digestion, these systems require smaller tanks than septic systems

Dark greywater is referred to as the water from dirty diaper loads, dishwashers, and
kitchen sinks

Greywater reuse opportunities are more limited than those of rainwater because of
increased threats from greywater pathogens

Glass is considered a high grade recyclable resource

Methane gas is a usable byproduct of landfill decomposition

The incinerator is unlikely to be used in the future as a waste disposal machine

A refuse baler/compactor can reduce trash to 10% of its original volume

The primary advantage of a vacuum based waste disposal system is that lines can be
small and contents can be moved horizontally and vertically

In urban settings the food disposal is used for composting for rooftop gardens

The exterior required area for trash collection in a residential building of 16-25 units is
48sq.ft.

A detached service core type is typically best for flexibility of rentable areas

A downfeed system is not pressurized, it feeds by gravity…
Mechanical Fire Safety
FIRE SAFETY PRIORITIES
Fire protection codes have 3 goals:
1. Afford protection or escape to the occupants of a building, by means of egress or “ a
place of refugee”
2. Insure sufficient structural integrity so firefighters may enter and fight without excessive
risk
3. Allow the building to survive a fire so it can be economically restored afterwards

There is a fourth goal that is becoming of more importance that is to prevent a
fire from starting.
Fire protection on buildings is accomplished in several ways:

Preventing fires

Early detection and alarms

Providing quick exiting of building occupants

Containing the fire

Suppressing the fire
BUILDING CODES
In order for the architect to determine the requirements he must classify a building by its
function, construction type and its location. Building codes set forth a minimum flame spread
ratings, establish flammability standards and similar constraints.
OCCUPANCY determines the degree of fire resistance required by the structure. The
occupancies are categorized and assigned a letter, A (assembly bldgs, theaters) B (offices,
factories, commercial) E educational etc. A number is also assigned which identifies a division
in the category, B2 occupancy.
CONSTRUCTION TYPE determines the degree of fire resistance. There are 5 construction
types, type 1(the most fire-resistive) to type 5(conventional wood stud)
LOCATION of the building on its property in relation to setbacks, alleys, public spaces, etc.
determines the fire resistance of the exterior walls.
FLOOR AREA of a building is limited. Buildings with more fire resistive construction are
allowed more floor area, also if the building is sprinkled, more area is allowed. The height and
number of stories are limited by the building construction. The number of occupants in based
on the occupancy and floor area.
COMPARTMENTATION is a critical concept in fire and life safety. The basic idea is to contain
a fire and limit it’s spread.
In order to permit mixed occupancies the construction of the walls separating them is also
specified.
When a design requires more sq.ft., than permitted the building is separated in two or more
portions, each of which must comply as a separate building.
In order for compartmentation to be effective all openings through the fire wall must be closed
with fire rated devices: doors, windows, ducts, etc.

For example the whole assembly of a door must be fire rated, door, frame, hinges,
mounting hardware, etc.
Fire assemblies must be self-closing or automatic.
SMOKE CONTROL is one of the most important aspects of fire protection. Smoke moves by
natural convection(warm to cool). The stack effect must be considered in tall buildings,
stairways, elevator shafts, mechanical shafts, etc. can become shafts. The same concept
compartmentation for fire must be applied for smoke. Devices such as fire dampers, gaskets
on fire doors, automatic closing, etc. must be used. There are two types of control passive and
active for smoke control. Passive is the use of devises that create compartments, an active
system is an engineered system that uses mechanical fans to produce pressure differentials
across smoke barrirers or to establish airflows to limit and direct smoke movement. Stairways,
vestibules can also be pressurized to prevent smoke from entering.
EXITS are required to egress to a public street or alley. Most buildings are required two or
more exits.
EXIT STAIRWAY must be within 150 ft of any point, 200 ft in a sprinkled building.
The minimum of an EXIT PASSAGE is 44” wide.
All DOORS must swing in the direction of travel and be unlatched or activated with panic
hardware
EXITS from all public spaces must be provided for handicapped persons
All EXIT STAIRWAYS must be fire resistive construction
Buildings that are 5 stories or more, or of type I and II construction, require a min. of two hours
construction
One hour rated walls are acceptable for other construction type
Buildings greater than 75ft in height one of the exit routes must be a smokeproof enclosure,
sometimes called a smoketower
CLASSES OF FIRES
Fires are divided into 4 classes:

Class A- ordinary materials, including wood, paper, cloth and rubber. They can be
extinguished with water.

Class B- involve flammable gases and liquids, such as natural gas, gasoline, oil, etc.
they tend to float on top of water, making it ineffective to extinguish them.

Class C- involves electrical equipment. The extinguishable medium must be electrically
non-conductive, water is not acceptable. After the source of electricity is disconnected
class A or B extinguishers can be used.

Class D- involve combustible metals like sodium, potassium, etc., they require special
extinguishers. Sodium at room temp. can burst into flames in contact with water.
HALON is a special medium used, it’s not toxic for brief exposures. It displaces oxygen. When
used audible and visible alarms should be used to warn personnel to leave.
FIRE DETECTION
There are 3 forms of fire detection:

ION DETECTORS; ionization detector responds to the chemical products of
combustion present in the air, even in the early stages. The problem is that they also
detect smoke from the kitchen or smoker.

PHOTOELECTRIC SENSORS; photoelectric detector reacts to visible smoke that
blocks a beam of light. They may miss early stages of fires. The ion detectors have
over passed them in the present.

HEAT ACTUATED SENSORS; are less sensitive. Several ways to do this. The most
simple is a piece of wax or paraffin.
FLASHOVER is a phenomenon. Small or smoldering fires release gases, which often are at
very high temperatures and collect near the ceiling. The materials become extremely hot and
when they reach combustion temperatures they fire all at once, sometimes even with an
explosion can occur.
Other things that a fire alarm can activate are:

Actuating remote alarms, in the building or fire station

Actuating other extinguishing systems

Overriding elevator controls

Closing fire doors, dampers and this way controlling fire migration

Varying fan speeds
STANDPIPES
DRY STANDPIPES are normally empty and not connected to a water supply. The lower end
terminates at street level (Siamese fitting) where the fire department connects it to a fireplug
via a pumper truck, which is capable of pumping water through the pipe. The Siamese fitting
can accept 2 or 4 hose connections. A 2 ½” outlet connection must be provided at every floor.
The equipment is a portion of the fire department. The firemen must carry the hoses to the
connections, a ball drip is located at the lowest point of the system to ensure that it remains
dry.
WET STANDPIPES are required in buildings 4 stories or more in height, theatres and places
of assembly of 300 or more people, all hazardous occupancies and group B occupancies.
They are provided for the use of the occupants but they must also be equipped with Siamese
fittings so the fire department may supply additional pressure. Wet standpipes must be located
in a building so that every point of every floor is within 30ft of the end of a 100ft hose attached
to an outlet. The system must be designed to supply 35gpm at 25psi for a minimum of 30
minutes.
Buildings that exceed 150ft in height require a combination standpipe for every stairway or
smokeproof tower which extends from the ground to roof.
SPRINKLER SYSTEMS
WET & DRY SYSTEMS; the simplest of systems that consist of a pattern of sprinkler heads,
each equipped with a fusible plug or link. In the event of a fire the fusible plug will melt. The
WET pipe system has the advantage of quick response, however it can freeze. The DRY pipe
system the sprinkler piping is dry between the dry pipe valve and all the sprinkler heads. The
pipes are filled with compressed air. The pipe valve may be located in a warm enclosure. The
disadvantage is that there is a delay for the water to come out of the sprinkler head.
DELUGE SYSTEM; the system floods the whole space with water. The sprinkler heads are
always wide open, but the pipe system is dry. A fire detection system inside the space
activates a valve that releases the water.
PREACTION SYSTEM; is a variation of the dry system that requires both the sprinkler head
be activated and an independent fire sensing device be triggered. The water is allowed into
the system before any sprinkler head is opened, at the same time an alarm is activated.

All sprinkler systems must also have a Siamese connection outside the building.