high rise plumbing design - Indian Plumbing Association

HIGH RISE PLUMBING DESIGN
RON GEORGE
Editorial Note: • Chapters mentioned in the article refer to US Plumbing Codes and not to UIPC-I
• Flushometer Valve is called as Flush Valve in India
H
igh rise buildings have very
complex
and
challenging
plumbing piping systems with
unique pressure issues and system
design issues that are typically an
engineered system. There is not much plumbing
code language in the model plumbing codes in the
United States that addresses high-rise building
plumbing design and there are no plumbing
system design standards that addresses how to
install plumbing systems in a high-rise building.
However, there is information available on high
rise plumbing design in plumbing design books
available from the American Society of Plumbing
Engineers (ASPE).
Website: https://aspe.org/
product-detail
When a building is built in a location where a
building code and other codes like plumbing,
mechanical electrical and fire codes are adopted
and enforced, the requirement to comply with a
code or standard is typically enforced by a local
ordinance or law. However, some jurisdictions
may not have people hired or trained to enforce
the codes. In countries or jurisdictions where
there is no adopted code, building owners and
construction managers typically agree, through
a construction contract, to use a specific code
from the US or Europe and rely on the engineers
to follow building, mechanical, plumbing,
fire protection and electrical codes and their
referenced industry standards. When there is not
a trade school available for each building trade,
and/or when there are no building inspectors
working for the jurisdictions to enforce the
requirements in the codes for each building trade,
the owner may rely on the construction manager’s
trade inspection experts or the engineers for each
trade for the building to provide construction
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/ August 2017 / Indian Plumbing Today
inspections. This is to assure conformance with
the codes and standards that they have contracted
and agreed with the owner to design and build in
conformance with.
Model Codes
The model plumbing codes in the United States
are developed by code organizations made up
of volunteers and paid staff. The codes are
developed in a series of hearings that allow ample
opportunity for people to comment on proposed
code changes before the code committees votes
on code changes. The model plumbing codes
address the maximum pressure allowable at each
fixture and the minimum pressure required at
each fixture and a few other things that could
apply to high-rise buildings, like requirements for
hot water at various fixtures and requirements
of maximum hot water temperatures flowing
from several types of fixtures, but the code does
not fully address hot water or cold-water system
sizing, storage sizing or temperatures, distribution
temperatures or distribution piping layout and
design. The code also does not address domestic
cold water booster pump sizing, booster pump
types, booster pump controls or the use of, or
maintenance of pressure reducing valves in highrise buildings etc. A few of the code requirements
are designed to limit pressure or temperature for
health & safety reasons. Excessive pressures can
cause vitreous china fixtures to violently rupture.
The plumbing code typically addresses health and
safety issues. There are not many design or code
requirements for saving energy, saving water,
and the codes generally do not address system
designs to related to sustainable design features
and efficiency other than water flow rates.
Life Cycle Cost Design Considerations
The plumbing system design can make a
significant difference in life cycle operating and
maintenance costs. Often, the least expensive
system to install uses the most energy and costs
more to maintain over the life of the building.
A single pump design using pressure reducing
valves on the lower floors can cost 4 to 5 times
more to operate than multi-pump water booster
systems with separate risers for each pressure
zone. Generally, the first cost is cheaper for the
single pump system. I have found in my 40 years
of experience that a developer will typically build
the building for the cheapest first-cost and will
sell it shortly thereafter because a developer is
not concerned with operating and maintenance
costs. Generally, developers are concerned with
profit, speed and ease of installation over quality
and lower operating and maintenance costs.
However, many institutional or corporate clients
will prefer the higher quality, more expensive
first-cost designs to reduce the operating and
maintenance costs for the life of the building.
The plumbing code language in the International
Plumbing Codes or Uniform Plumbing Codes
is very similar. They have requirements for
prevention of cross connections or backflow
prevention, they have minimum and maximum
pressure requirements, and specific requirements
for waste and vent stacks for buildings over
3 stories tall. There are many other code
requirements which would apply to high-rise
buildings, but the code is silent with respect to
system design issues mostly because the code
organizations do not want to be too prescriptive
with design requirements because they do not
want to be too design restrictive. The model codes
generally try to allow for modern technology or
new methods of construction if it is determined
that it provides an equivalent level of health and
safety.
lack of back-up or multiple pumps, lack of
multiple water heaters for back-up, systems that
exceeded the maximum and minimum pressure
zone requirements; water heater pressure zone
issues that caused the pressure relief valves to
constantly discharge water; domestic hot water
return pumping pressure, flow and system
balancing issues; and, drainage and vent stack
pressure issues. As you can see pressures are very
important in high rise buildings.
Pressure Conversions:
Pounds per square inch vs Kilopascals vs feet of
head vs meters of head
The pascal (Pa) or kilopascal (kPa) as a unit of
pressure measurement is widely used throughout
the world and has largely replaced the pounds per
square inch (psi) unit, except in some countries
that still use the imperial measurement system
or the US customary system, including the United
States where I live & work.
Converting Head Elevation to Pressure
The following equations are used to convert from
different units of measurements for pressure.
Converting head in feet to pressure in psi
Pumps characteristic curves in feet of head can be
converted to pressure - psi - by the expression:
p = 0.433 h SG
where:
p = pressure (psi)
h = head (ft)
SG = specific gravity of the fluid
0.433 = Conversion factor pressure psi
per foot of head
Converting head in meter to pressure in bar
This is where a specific design can lead to money
wasted because of equipment wearing out prematurely in high rise buildings. When a high
rise building plumbing system fails, it can leave
the building occupants without water and basic
hygiene for many hours or days if they need to
order special parts.
As an expert in plumbing system design, and
as a forensic investigator of plumbing and
mechanical system failures, I have investigated
many problems in high-rise buildings. The
problems have included: Booster pump sizing;
Pumps characteristic curves in meter of head can
be converted to pressure - bar - by the expression:
p = 0.0981 h SG
where:
p = pressure (bar)
h = head (m)
SG = specific gravity of the fluid
0.0981 = conversion factor for head in
meter to pressure in bar
Indian Plumbing Today / August 2017 /
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Converting head in meter to pressure in kg/cm2
Pumps characteristic curves in meter of head
can be converted to pressure - kg/cm2 - by the
expression:
Example - Converting Pressure - psi - to Pump
Head - feet
p = 0.1 h SG
where:
p = pressure (kg/cm2)
h = head (m)
SG = specific gravity of the fluid
0.1 Conversion factor from head in
meters to kg/cm2
Converting Pressure to Head
Since pressure gauges often are calibrated in
pressure - psi or bar - a conversion to the heads
commonly used in pump curves - like feet or
meter - may be required.
Converting pressure in psi to head in feet
The head in feet water column can be calculated
from pressure 100 psi as:
h = 2.31 (100 psi) / (1) = 231 ft
Where:
specific gravity of water = 1 feet of head water to psi
Pounds per square inch
The pound per square inch or, more accurately,
pound-force per square inch (symbol: Lbs/in2;
abbreviation: psi) is a unit of pressure. It is the
pressure resulting from a force of one pound-force
applied to an area of one square inch: One pound
per square inch is approximately 6894.757 Pa.
Kilopounds per square inch
2.31 = Conversion factor feet of hear
per 1 psi
The kilopounds per square inch (ksi) is a scaled
unit derived from psi, equivalent to a thousand
psi (1000 lbf/in2). kilopound per square inch
(ksi) are not widely used for gas pressures. They
are mostly used in materials science, where the
tensile strength of a material is measured as many
psi.
The conversion in SI Units is 1 ksi = 6.895 MPa, or
1 MPa = 0.145 ksi.
Converting pressure in bar to head in meter
Elevation Head Pressure Facts:
h = 2.31 p / SG
where:
h = head (ft)
p = pressure (psi)
SG = specific gravity of the fluid
h = p 10.197 / SG
where:
h = head (m)
p = pressure (bar)
SG = specific gravity of the fluid
10.197 = Conversion factor for pressure
in bar to head in meters
For every foot (0.3048 Meters) in elevation, a
water column in a pipe can build up 0.433 pounds
(2.9854299 Kpa) of pressure.
So for every story of 10 feet (3.048 meters) there is
a 29.8542Kpa increase in pressure
PSI Pressure Conversions:
Converting pressure in kg/cm2 to head in meter
psi↔pa
1 psi = 6894.744825 pa
psi↔kPa
1 psi = 6.894745 kPa
where:
psi↔cPa
1 psi = 689474.482549 cPa
h = head (m)
psi↔mPa
1 psi = 6894744.825494 mPa
p = pressure (kg/cm2)
psi↔uPa
1 psi = 6894744825.494 uPa
psi↔N/m2
1 psi = 6894.744825 N/m2
h = p 10 / SG
SG = specific gravity of the fluid
2.31 = Conversion factor for pressure
in psi to head in feet
For example: For converting Pump pressure in
feet of head to pressure in psi
The pressure - psi - of a water pump operating
with head 120 ft can be calculated as:
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p = (120 ft) 1 / 2.31 = 52 psi
/ August 2017 / Indian Plumbing Today
psi↔Bar
1 Bar = 14.5038 psi
psi↔mbar 1 psi = 68.947448 mbar
psi↔ubar 1 psi = 68947.448255 ubar
psi↔kgf/m2 1 psi = 703.068306 kgf/m2
psi↔kgf/cm21 kgf/cm2 = 14.223595175051 psi
psi↔kgf/mm2 1 kgf/mm2 = 1421.9411764706 psi
psi↔gf/cm2 1 psi = 70.30683 gf/cm2
psi↔lbf/in 1 psi = 1 lbf/in
2
psi↔ksi
2
1 ksi = 1000 psi
psi↔msi
1 msi = 1000000 psi
psi↔lbf/ft2 1 psi = 144 lbf/ft2
psi↔lbf/yd2 1 psi = 1296 lbf/yd2
psi↔torr 1 psi = 51.71484 torr
psi↔cmHg 1 psi = 5.171484 cmHg
psi↔mmHg 1 psi = 51.71484 mmHg
psi↔inHg
1 psi = 2.036025 inHg
psi↔Inch mercury (60F) coefficient: 2.041768
psi↔inAg
1 psi = 27.680622 inAg
psi↔ftAg
1 psi = 2.30672 ftAg
psi↔atm
Developer vs Owner Construction
1 atm = 14.695975011122 psi
Ksi Pressure Conversions:
ksi↔pa
1 ksi = 6894744.825494 pa
ksi↔kPa
1 ksi = 6894.744825 kPa
ksi↔cPa
1 ksi = 689474482.5494 cPa
ksi↔mPa
1 ksi = 6894744825.494 mPa
ksi↔uPa
1 ksi = 6894744825494 uPa
ksi↔N/m 1 ksi = 6894744.825494 N/m2
2
ksi↔Bar
1 ksi = 68.947448 Bar
ksi↔mbar
1 ksi = 68947.448255 mbar
ksi↔ubar
1 ksi = 68947448.25494 ubar
ksi↔kgf/m 1 ksi = 703068.306237 kgf/m2
2
ksi↔kgf/cm21 ksi = 70.305713 kgf/cm2
ksi↔kgf/mm2 1 kgf/mm2 =1.4219411764706 ksi
ksi↔gf/cm2 1 ksi = 70306.829934 gf/cm2
ksi↔psi 1 ksi = 1000 psi
ksi↔lbf/in 1 ksi = 1000 lbf/in2
2
ksi↔msi
1 msi = 1000 ksi
ksi↔lbf/ft2 1 ksi = 144000 lbf/ft2
ksi↔lbf/yd2 1 ksi = 1296000 lbf/yd2
ksi↔torr
1 ksi = 51714.840249 torr
ksi↔cmHg 1 ksi = 5171.484025 cmHg
ksi↔mmHg 1 ksi = 51714.840249 mmHg
ksi↔inHg 1 ksi = 2036.025042 inHg
ksi↔Inch mercury (60F) coefficient: 2041.768364
ksi↔inAg
1 ksi = 27680.62163 inAg
ksi↔ftAg
1 ksi = 2306.719618 ftAg
ksi↔atm
1 ksi = 68.045842 atm
The code is a minimum, so it does not address
many of the performance and energy savings
issues that make good engineering sense for an
20
energy efficient or sustainable plumbing system.
Some of the common problems that I find when
investigating problems in high-rise building
plumbing systems are domestic cold and hot
water system pressure zone problems. Problems
occur when the designer or contractor fails to
pay attention to the minimum requirements
for pressure and maximum requirements for
pressure in a plumbing system. These pressures
limitation are what establish pressure zones
within buildings. Most problems in high rise
systems occur when people try to stretch these
pressure zones or when they try to circulate hot
water through pressure reducing valves.
/ August 2017 / Indian Plumbing Today
The model plumbing codes are a minimum
document for health and safety and they are not
developed to address all the engineering issues
associated with high-rise buildings. Another issue
is, most high-rise buildings are built by developers
who want to build a building for the cheapest
first cost without any concern for energy or
maintenance costs. A developer wants to build
it as cheap as possible, some even get it certified
as being green in order to market it to people as
energy efficient and then sell it to someone else
who will have to deal with the high energy and
maintenance costs over the life of the building.
Often these developer-built high-rise building
use four times as much energy as a building with
a properly engineered domestic water booster
pump system.
A typical developer-built high-rise building
may have a single or duplex booster pump in
the basement serving the entire building with
pressure reducing valves on all of the lower floors
where the supply pressure exceeds 80 psi. This
type of system design with a single booster pump
package and pressure reducing valves is a very
energy and maintenance inefficient plumbing
system, but many buyers/owners are stuck with
this design if they buy a building with this design
concept.
Pressure Reducing Valves = Energy Wasting
Valves
Most of these developer-built buildings have
pressure reducing valves or what I call “Energy
Wasting valves” on the bottom floors. On the top
of the building, the upper floors do not require
pressure reducing valves. This design will waste
hundreds of thousands of dollars or millions of
dollars in energy over the life of the building,
depending on the building size. I have always
said if you have pressure reducing valves in your
design, it is not a Green plumbing system design.
I would like the green certification programs to
consider not awarding certifications to a building
utilizing PRVs because of their massive energy
waste. They should take points away for every
floor operated downstream of a PRV in a highrise water distribution system. There are some
exceptions for Pressure reducing valves to reduce
normal water pressures down to lower pressures
for make-up water to hydronic systems, final
rinse water in dishwashers, etc.
There are different quality levels of valves and
pumps, and, often in the developer-built buildings,
the valves and pumps may be of the lower quality,
less expensive type that tends to fail more often.
The pumps in this type of design tend to have
seal failures and leaks; the lower quality pressure
reducing valves typically experience wear on the
seats, especially as the pressure differential grows.
Even high-quality pressure reducing valves will
experience problems with significant pressure
differentials across the valve seat. The pressure
differentials can be addressed by reducing the
pressure in stages, which the developers typically
do not want to spend the money on. When the
pressure reducing valve wears out, this is often
referred to as wire drawing. This causes more
money to be spent purchasing replacement parts
and more money to be spent on labor to replace
the pumps and pressure reducing valves. Wire
drawing of valves occurs when high velocity
water shoots across the seat of a control valve and
any sediment or scale in the water can score the
less expensive (softer) valve seats. After a brief
period of time, it looks like someone took a hack
saw or wire saw and cut a groove in the valve seat.
As the valve continues to wear, it loses its ability
to maintain downstream pressure, and, during
periods of non-use, the downstream pressure can
reach the same pressure as the upstream pressure.
This can lead to exploding toilets, bursting pipes,
flooding, leaking faucets and toilets, which is
a significant waste of water when the supply
pressure goes from 60 pounds per square inch to,
say, 360 pounds per square inch.
Pipe Pressure Ratings
There are different categories of high rise
buildings as far as design of the water system is
concerned. The taller the building is, the higher
the pressure rating will be required for the
pipe, valves and fittings. Each pipe material has
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different pressure classifications. It is important
to make sure you are using the correct pressure
classification for a high-rise building.
Often
in these developer-built buildings, the water
riser is rated at a higher pressure and all piping
downstream of the pressure reducing valve is
rated at the lower pressure rating. When the
pressure reducing valve on a lower floor fails the
higher pressure is exposed to the lower pressure
rated pipe, valves, fittings and fixtures. The ideal
or green and sustainable plumbing design would
not use pressure reducing valves. (energy wasting
valves).
The plumbing designer should determine the
minimum required pressure for the governing
fixture on the top floor and make sure the
minimum pressure will be maintained during
peak flow periods. The designer must also
consider the maximum allowable pressure in the
plumbing system which is 80 PSI in most model
codes in order to protect vitreous china fixtures
from damage. If the most demanding (governing)
plumbing fixture at the top of the building requires
35 PSI minimum at the top of a pressure zone and
the highest pressure allowable per code at the
bottom of the pressure zone is 80 PSI a building
with floors ten feet (3.048 meters) apart can
have about nine or ten floors per pressure zone
depending on the friction loss and pipe sizing. The
elevation head pressure and allowable friction
loss associated with the pipe sizing will dictate
how many floors should be in a pressure zone. In
the above example if the pipe sizing is generous,
then there can be ten floors. If pipe sizing is
smaller and velocities and corresponding friction
losses are higher, then only nine floors should be
in a pressure zone. For example: Elevation head
loss is 0.433 per foot of elevation. If the floors are
10 feet from finished floor to finished floor the
elevation pressure loss for every floor will be 4.33
pounds per square inch (29.854299 Kpa per floor).
The key here is to have enough water pressure on
the top floor of a pressure zone to allow the fixture
to operate as designed.
The codes address the minimum pressures at the
fixtures and they address maximum static water
pressures in the water distribution system where
they require water pressure reducing valves or
regulators where the water pressure exceeds
80 pounds per square inch (psi). The Plumbing
fixtures listed in chapter 6 of the model plumbing
codes list minimum flowing pressures or residual
pressures at each fixture. For example, a bathtub,
shower or bidet requires a minimum of 20 psi
flowing pressure. That would likely be about 22
psi static pressure. A water closet, siphonic type,
flushometer valve requires a minimum of 35 psi
residual (flowing) pressure. The newer 1.6 and
lower water closet tank type fixtures requires 20
psi where the older higher flow models required
a minimum pressure as low as 8 psi. Many newer
models of water conserving water closets rely
on the water supply pressure to force the flow
into the bowl and trap as part of the design and
operation of the fixture with minimum pressures
as high as 45 psi. If the minimum and maximum
pressures are not adhered to problems are likely
to occur.
have led to significant flood incidents with tens of
millions of damages in high rise buildings when
pumps have been started-up after a period of
down time. If there is a power outage or even
a planned outage for draining the piping and
replacing pressure reducing valves, which occurs
many times per year with the PRV designs. The
maintenance personnel must be trained to follow
pump manufacturer’s start-up procedures when
a domestic water booster pump system has shutdown long enough for the water to be drained
from the riser (more than a few minutes). Some
pump controls are designed to require a manual
start-up after a power failure for this reason.
Maintenance issues
2As with any type of building that has full
time maintenance staff some of the problems
associated with plumbing system failures begin
with the hiring of the maintenance staff. If the
building owner does not hire properly trained or
certified maintenance staff, the owner should at
least pay for or encourage their staff to seek out
training that addresses the care and maintenance
for the systems they are hired to maintain. I have
seen many failures where the maintenance staff
contributed to the failure because they did not
know what they were doing. For example: firing
a boiler before opening the water fill valve. Then
realizing they forgot to fill the boiler with water
then opening the fill valve and letting cold water
rush into a red hot boiler. Boom! The owner just
bought a new boiler.
Domestic water Pressure Booster Pump Start-up
Another common failure is when there is a
prolonged power failure and the tenants in the
building can drain the water from the piping
system before the power is restored.
The
maintenance staff must shut-down the domestic
water booster pumps so that they do not startup with no water in the riser. I have seen the
results of pump start-ups that were not done
properly and it can blow the piping apart causing
flooding. If a pump starts up with no water in
the downstream piping, there is no backpressure
on the pump, so it will operate at the end of the
pump curve. This increases the flow volume
significantly and the velocity increases also. It
is not unusual to see water velocities close to
12-15 feet per second which will pack a whale
of a punch when the water in the pipe gets to a
fitting like an elbow or tee. The rule of thumb
for water hammer is 60 times the water velocity
is the potential water hammer pressure spike
that can occur. Many failed large diameter pipes
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Water hammer will occur when a pump starts-up
and must be controlled by turning off the pump
during the outage and closing off all the valves.
When the power is restored, the maintenance
staff must open a faucet or two at the top of the
building (or utilize an automatic air vent) to vent
out the air from the high points in the system and
then partially open one valve on the booster pump
package and manually run one (smaller) pump
until water comes out of the fixture(s) at the top
of the building. This will slowly introduce water
into the system to prevent the water hammer
associated with all of the booster pumps coming
on with an empty pipe which can blow apart the
pipe or fittings and flooding a high rise building.
Pressure Zones to Avoid High Pressure Rated
Pipe, Valves & Fittings
There are several ways to design the water
distribution system in a high-rise building. The
most efficient system design utilizes a separate
booster pump for each pressure zone in the
building up to about 40-60 stories in height
(depending on floor to floor height). When the
height of the building gets much higher the
pressure rating of the pipe, valves and fittings
must be higher and the cost goes up. In ultra-highrise designs they often use a water supply pipe to
a suction tank for a higher zone domestic water
booster pump and piping system to begin with a
higher-pressure zone which may feed the suction
tank for even higher-pressure zones if needed.
There are many additional issues with these
types of ultra-high–rise systems that may include
by-pass valves, isolation valves, overflow drains,
relief valves, etc. This allows lower pressure pipe,
valves and fittings to be used on the lower floors
of ultra-high-rise buildings.
For buildings that utilize 300 psi fittings and
below (Maximum height 40-60 floors depending
on floor to floor height) multiple booster pumps
with dedicated risers for each pressure zone could
be used for each pressure zone with no pressure
reducing valves. This saves a lot of energy as
compared to a single large booster pump which is
designed for the full flow and head requirement
for the building.
Using one pump with pressure reducing valves
would be like carrying many large buckets of
water up 100 flights of stairs so that someone can
take a sip of water then pour all of the rest of the
water down the drain or out a window. There
was a lot of energy wasted carrying all that water
up to the top floor when only a six-ounce cup of
water was needed to satisfy the demand for a
drink. This is what happens when a very large
booster pump package is installed at the base of
a high-rise building and pressure reducing valves
are used to reduce the pressure on the lower
floors. It wastes tons of energy!
Maintenance Staff Training issues
I stayed on the top floor in a high-rise hotel
building in Florida not long ago. I had an early
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flight so, I woke up at 3:45 am to get ready for
my flight. When I got in the shower, there was
a gurgling sound when I turned on the faucet,
but no water was coming out. I tried the sink,
not water, more gurgling sounds. It sounded like
the faucet was sucking air in instead of flowing
water out. I packed up, took the elevator down
to the ground floor and drove my car around the
complex to the front lobby. As I was driving, I
noticed all of the irrigation zones were flowing
at the same time which were apparently on the
domestic cold water booster pump. This must
have used up all the pressure needed to raise the
water up to the upper floor, where I was staying.
The irrigation system was apparently on the same
domestic water booster pump as the hotel rooms
in the tower.
I stopped by the front desk to let them know about
the problem and suggested they adjust the timing
on their sprinkler zones so that they don’t all go off
at the same time. The maintenance guy showed
up while I was checking out and I told him, I could
not get any water from the shower this morning
and he said he would go check the boiler & turn
the hot water temperature up. I explained the hot
water temperature was not the problem, it was
the sprinkler system and too many zones were
flowing at the same time. I explained that the
domestic water system at the top of the building
was being starved by all the sprinkler zones at
the ground level flowing simultaneously. At
that moment, he reminded me that he had been
working there for over 5 years and he worked his
way up the building maintenance and he knew
what he was doing and he assured me it was a
boiler thermostat problem. I told the maintenance
man that I checked the two-handled sink faucet
and no water came out of either the hot or cold
water. I told him it was only the gurgling sound
of air rushing in so in was probably not a water
heater temperature problem. His eyes closed as
he seemed to be trying to comprehend what I just
told him. He mumbled something like he was still
going to check the boiler temperature anyway as
he walked away. This made me wonder if there
were a lot of problems with the hotels water
temperature in the past and this guy would run
down to the boiler room and adjust the water
heater temperature.
On the plane, I wrote a letter explaining the
problem and the hotel chains chief engineer
replied to my letter and he explained they changed
the cartridge in the room and that should take
care of it. I had to follow up with another letter to
explain it to the hotel engineer that changing the
cartridge would not solve the problem.
Material substitutions
There have been lots of cases where material
substitutions have been made. It is important for
the engineer, contractor and owner to verify the
pressure ratings, thermal expansion properties
and temperature ratings of the substituted
materials to make sure the piping is installed
in accordance with the pipe manufacturer’s
instructions. In one high-rise building near
New York City, CPVC plastic pipe was installed
for the domestic hot water piping in a very tall
building. When the water heaters were turned
on and hot water started flowing, the linear
thermal expansion of the riser pipe was such that
the pipe grew upward almost 2 feet (0.6 meters)
and snapped off a branch pipe on an upper floor
causing tens of millions of dollars in water damage
on lower floors.
Do Not Circulate Through Pressure Reducing
Valves
I have seen many high-rise building designs
where the water heaters are located in the ground
floor or in a penthouse. In these poorly designed
buildings, as the water riser goes up in the building
it has pressure reducing valves on the lower
floors. When the hot water system is distributed
this way, there is no way for circulation of the
domestic hot water across the pressure reducing
valve. In many cases the inexperienced designer,
contractor or developer discovers this after the
building is built. Then a re-pressurization pump
is added on every floor to inject the hot water
return back into the hot water return system
so the water can flow back to the water heater.
These systems are the worst energy violators of
all. Pressure reducing valve usually don’t last
very long in hot water service and are constantly
being replaced. The best solution is to provide
local water heaters, If you are going to use central
water heaters, the solution is to design the system
with the water heater within the pressure zone.
Many of these issues should be considered for
inclusion in the green codes or energy codes. At
the very least when designing or constructing
high-rise buildings we should strive to address
ipt
these issues before the building is built.
Mr. RON GEORGE, CPD President of Plumb-Tech
Design & Consulting Services, LLC and is involved in
Plumbing, Piping, Fire Protection and HVAC System
Design & Consulting Services; 2D AutoCAD & 3D Revit
CAD Services; 3D Building Information Modeling
(BIM); Forensic Investigations of Plumbing, Piping, Fire
Protection & Mechanical System Failures; Litigation
Support, Technical Report Writing; Code & Standard
Consulting; Training Seminars: Plumbing, Mech., Fire
Protection Design, Codes & Standards.
Indian Plumbing Today / August 2017 /
27
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