Plumbing
The graduate student housing building is classified as an Occupancy Group R-2, according to the International Building Code (IBC). The 12 floors of the graduate student housing building contain a total of 185 apartments; some of the apartments have one bedroom while others have two or three, but all apartments each have one kitchen, one bathroom, and one living room. Each bathroom contains the following plumbing fixtures: a water closet, a shower, and a sink. Each kitchen contains the following plumbing fixtures: a dishwasher and a sink.
The fixture to apartment ratio is 1:1; there are 185 water closets, 185 showers, and 185 bathroom sinks. There are 185 kitchen sinks and 185 dishwashers. In order to account for possible miscellaneous fixtures throughout the building, each quantitative fixture number was increased from 185 to 190. Additionally, according to the IBC there will be 10 washing machines throughout the building. This number was found from the table above, in which it states there needs to be a washing machine per 20 apartments.
Total Fixtures
In order to calculate the total supply flow rate for the entire building, first the water supply fixture units (WSFU) per each fixture needed to be found. The table below to the right from the International Plumbing Code (IPC) displays the WSFU for fixtures commonly found in residential buildings. The table below to the left displays the total number of fixtures, the WSFU from the adjacent table, and the total. The total was found by multiplying the total number of each type of fixture by the associated WSFU.
Flow Rate
A water usage calculator, found on Kohler's website was used to determine the total flow rates. Certain variables were input in order to get an estimate of the flow rates. The first variable assumed was that there was on average two residents in each apartment. The next assumption was that each water closet used 1.6 gallons per flush and each person flushed the toilet 5 times a day, which is the average according to recent studies. The shower fixtures were assumed to use 2.5 gallons per minute (GPM), which is the current max flow rate allowed by the U.S. government. Each shower taken was assumed on the safe side to be 9 minutes long (U.S. average is 8.2 minutes per shower), and it was assumed that each person takes one shower per day. The bathroom and kitchen sinks were assumed to consume 2.2 GPM, which is the current max flow rate allowed by the U.S. government. The sink use per person per day was assumed to be 3 minutes, which is the average according to a study done by Delta Faucet. There are washing machines present within the building, and it was assumed that their flow rate was 15 gallons per day (this was a value that could not be changed). There are dishwashers present in each apartment, and it was assumed that their flow rate was 1 gallon per day (this also is a value that could not be changed).
The table below to the right displays the data returned to us after the simulation was done, along with a comparison to the us average and if unit was LEED certified. The simulation run was for a single apartment unit. The values were then multiplied by 185 (number of total apartment units) to get the flow rate through all apartments. To obtain flow rates for miscellaneous fixtures, such as public restrooms, throughout the building that were not accounted for, the flow rate values were multiplied by 5. The miscellaneous values were then added to the total apartment unit values to get a total flow rate value for the entire building. The table below to the left contains the data returned through the calculations, along with the conversions of how much water is used per minute, per hour, per day, per month, and per year.
The table below to the right displays the data returned to us after the simulation was done, along with a comparison to the us average and if unit was LEED certified. The simulation run was for a single apartment unit. The values were then multiplied by 185 (number of total apartment units) to get the flow rate through all apartments. To obtain flow rates for miscellaneous fixtures, such as public restrooms, throughout the building that were not accounted for, the flow rate values were multiplied by 5. The miscellaneous values were then added to the total apartment unit values to get a total flow rate value for the entire building. The table below to the left contains the data returned through the calculations, along with the conversions of how much water is used per minute, per hour, per day, per month, and per year.
Pipe Sizing
The pipe sizing was determined using the flow rate chart above, along with the two charts below. The minimum outlet sizing for PVC pipe can bee seen on the chart below to the right. Every type of fixture that is present within our building has a minimum outlet pipe sizing of 1/2 inch. According to the chart above, the simulated gallons per minute for the entire building is slightly greater than 17 GPM. The assumed pressure used was average (20-100 psi) because of the 60 psi intake from the street. Using the chart below to the left, the pipe size would have been sufficient at 3/4", but in order to protect against human error and other possible irregularities it was decided that a 1" pipe would be best.
Daily Hot and Cold Water Usage
Every shower and dishwasher, along with every sink, both in the kitchen and in the bathroom require hot water to them. As a result, there are a total of 740 fixtures (185 of each fixture type) that will need to have a supply of hot water. According to the table above, each person consumes on average about 64.7 gallons per day. There are 370 assumed occupants and the assumption of 64.7 gallons/day per occupant, adds up to about 24,000 gallons per day for the occupants. The total fixture units of hot water needed is 1520 out of the total 2110, which is approximately 70 percent of the total water usage. The hot water usage was calculated by multiplying the 24,000 gallons per day by 70% which is about 16,800 gallons per day of hot water and as a result, the cold water usage was 7,200 gallons per day.
Components of System
The building will be supplied by water coming from the streets at a pressure of 60 psi. Piping will feed the water from the street to the basement of the building and through its associated components. A chilled water system of piping will feed to all sinks, water closets, showers, dishwashers, and washing machines. A domestic hot water system of piping will feed to sinks, showers, and dish washers in all apartment units. The cold water is converted into hot water through the use of heaters, which minimizes the heat loss and promotes an efficient system.
In order to maintain proper indoor air quality (IAQ) levels and adequate ventilation, a vent stack on the roof and a waste drain line of piping are used. The drain piping will collect all used water supply and transfer it out of the building.
In order to maintain proper indoor air quality (IAQ) levels and adequate ventilation, a vent stack on the roof and a waste drain line of piping are used. The drain piping will collect all used water supply and transfer it out of the building.
System Interaction
The plumbing system mainly interacts with the storm water system, through the green roof and the permeable pavement surrounding the entire site. The plumbing system also interacts with the HVAC system, through the heaters that are used to heat the chilled water to domestic hot.
Green Water Management Techniques
Due to Drexel’s newly adopted “Green Initiative”, it was decided that the use of green technology should be incorporated with the new graduate student housing building. A major green technique used was the incorporation of a green roof. The roof would be completely covered with vegetation to present a growing medium. The medium is placed on top of a waterproofing membrane, along with a drainage barrier. The green roof could collect runoff and store the excess water in a cistern somewhere on the site in order to lower energy cost and consumption, and create a smarter building. The green roof can also potentially extend the lifespan of a roof by over 20%, and increase the real estate value of the building.