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I have seen a lot of changes in the plumbing codes since 1978, but the laws of physics have not changed. I joined ASPE in 1979, and I joined many other plumbing, mechanical, fire protection industry and code and standard writing organizations soon after.
Since the late 1970s, I have attended many college classes, manufacturers seminars, and plumbing industry design, code and standard review seminars. I also had the opportunity to attend a plumbing apprentice program in the early 1980s.
Many of these classes taught the basic science, fluid dynamics and hydraulics, thermodynamics, heat transfer, material sciences and the laws of physics associated with plumbing and mechanical systems. They also taught the code language in the late 1970s. Much of that code language has changed now, but the laws of physics are the same.
Some of the basics of plumbing are as follows.
Facts about water
One gallon = 231 cubic inches = 0.13368 cubic foot and one gallon weighs approximately 8.34 pounds
One cubic foot = 1,728 cubic inches = 7.481 gallons (7.5 for simplified calculations) and water weighs 62.4 pounds per cubic foot (62.5 for simplified calculations)
1 U.S. gallon = 3.785 liters; 1 liter = 0.264 U.S. gallons (a liter is slightly more than a U.S. quart)
1 cubic foot = 28.317 liters
1 cubic meter = 1,000 liters = 35.315 cubic feet
Water measurement units
There are two conditions under which water is measured: static water or volume and flowing water, expressed in a given volume over a time period. In plumbing, we typically express flow in gallons per minute or liters per second.
Flow units for water
One gallon per minute = 0.06309 liters per second (l/s) or 0.00223 cubic feet per second (approximately 1/450)
Water heating basics
One British Thermal Unit (BTU) is equivalent to the amount of heat required to raise one pound of water 1°F. Knowing this, if we have a calculated demand of 80 gallons of hot water at 140°F for a commercial kitchen, and we use the lowest average cold water temperature we see, (typically February, which is around 40°F in my area), to raise the temperature up to 140°F for a storage temperature that will control Legionella bacteria growth, the calculation will be as follows.Temperature rise: 40°F to 140°F = 100° F
Volume of water to be heated = 80 gallons x 8.34 pounds per gallon = 667.2 pounds of water x a 100 degree rise = 66,720 BTUs
If you are using a gas water heater and you know the efficiency of the water heater, you should adjust the BTU/h requirement to satisfy the calculated demand based on the gas water heater efficiency. In this example, the water heater efficiency is 80 percent, so we could calculate: 66,720 BTUs/0.80 percent efficiency = 83,400 BTUs required to raise 80 gallons of water from 40°F up to 140°F with an 80 percent efficient water heater. At a cost of $1.10 per hundred cubic feet of gas (ccf) the water heating cost for raising the hot water temperature is approximately $0.80 (about 80 cents) per peak demand period.
Piping losses are not considered in this calculation, but will add to the BTU requirements. Piping losses can be significant for hot water that is flowing through uninsulated piping, especially if the ambient temperatures of the space are lower and where the end use application is a considerable distance from the water heater. New construction and the energy codes now require insulation on all hot water pipes in commercial buildings.
Flow in sloping drains and stacks
In many of the plumbing classes, they taught us about flow in sloping drains and flow in vertical stacks. The velocity is much higher in the vertical stacks, and the water or waste clings to the walls of the pipe with the cohesion effect. When the water reaches the base of the stack and turns horizontal, the flow velocity reduces and a hydraulic wave develops, which is referred to as “hydraulic jump.” The hydraulic jump occurs within 10 pipe diameters of the base of the stack, and special venting provisions must be done to allow air to vent or escape from the area near the base of the stack when pressure waves are caused by slugs of waste falling in the waste stack. This allows air to avoid blowing out fixtures or p-traps near the base of a stack where the hydraulic jump may be occurring due to sustained flow.
There are many formulas that researchers used to develop the sizing charts and flow curves and venting requirements that are in the codes. We also learned about the Hazen-Williams formula for calculating friction loss in water pipes, and the Manning formula for calculating the flow velocity in a sloping drain, given the diameter of the drain, the slope of the drain and the material coefficient of roughness. From this information, a calculation can be done to show the flow velocity for half-full and full pipes. For other flow depths, you can use the velocity times the area of the depth of flow to calculate the approximate flow in cubic feet, which can be converted to gallons per minute. There are many other things that are covered in these classes—far beyond the space available here.
In 37 years, I have attended many hours of training related to plumbing, including many classes based on the physics of plumbing. In all these years, the laws of physics have not changed, but the codes have changed many times. I also learned about plumbing codes and standards and the process of how plumbing codes and product standards are developed. In many cases, an industry organization, manufacturers, or a laboratory or governmental entity may be given the opportunity to appoint a person to represent their interests on the code committees at the code hearings. Often, this appointment is given to someone who may be familiar with their particular product or position, or an interest group. If, for example, the appointee represents the widget industry, they will likely know a lot about widgets. But, they may have a limited understanding of the science and physics of plumbing and plumbing in general, depending on their background.
I have always said, “The science of plumbing, including the laws of physics, does not change when you cross a state line or city limits.”
But with respect to the codes, the laws and ordinances can change when you cross state lines or jurisdictional borders, and they continue to change every three years. There are typically hundreds of plumbing code changes each three-year code change cycle. I have seen some codes allow something in one code cycle, then the code language will flip-flop and not allow it in the next cycle, and then it will change back again in yet another code cycle. This is because the codes are based on a voting process, which involves various interest groups—so all it takes is someone to present compelling testimony during the few minutes allowed for testimony at the hearings, and that may convince enough people on the code committee to vote for a proposed change. There are even differences between all of the model plumbing codes, which leads to a greater likelihood that code requirements will change from one jurisdiction to the next.
Unfortunately, the laws of physics or health and safety concerns do not always prevail in the voting process. For the majority of code changes, the committees do the right thing and the code changes protect the health and safety of the public. In some cases, the cost associated with implementing the code change seems to carry more weight with certain interest groups than the health and safety benefits of implementing the code change. For example, someone could propose a code change to say, “All drains shall slope uphill and all waste shall flow uphill,” and provide compelling testimony to support the change. The laws of physics will not allow this to occur without a pump or lift station. But, it is possible for the codes to mandate such language, which could be a violation of the laws of physics. When something does get off track, there is a second round of code hearings where, most of the time, an errant code change proposal can be corrected. But not always.
I encourage everyone to get involved in the code change process and attend the code hearings. The International Code Council (ICC) will have code change commentary hearings for plumbing, residential, and mechanical, from September 30–October 1. The International Association of Plumbing & Mechanical Officials (IAPMO) is scheduled to call for code change proposals to be submitted for the 2018 Uniform Plumbing Code (UPC) after September 3 and before January 4, 2016.
Code change politics
There have been many code changes that I have come across that make me ask, where did that come from, and why is that language in the code? Sometimes, there seems to be no scientific explanation for a code change. If you dig deeper, and pay attention to testimony at the code hearings, you can usually deduce why a code change is the way it is.
There are groups that influence the code for political reasons, and the testimony is not based upon scientific or health and safety reasons. It is sometimes a turf protection issue; or sometimes it could be a manufacturer trying to get a marketing advantage in the codes by promoting their product or restricting their competition. Most of the time, the code committee eventually realizes what is going on and they address it properly. When there is poor code language, a code official is put in the awkward position of defending or enforcing poor code language.
Designing plumbing for buildings in different cities for national companies
Over the years, I have worked for several major retailers that designed big box hyper-marts and stores for sites all over the country. These companies had several master plans with different floor plan sizes based on the size of the city or geographic region where the stores were to be located. These master plans had about eight different store sizes based on the demographics of a given area. In addition, each floor plan size had options for left-hand and right-hand versions. They also had modular retail spaces around the front and side perimeters of the buildings in various sizes and left- and right-hand versions.
The modular retail spaces included options for automotive parts sales and service facilities, garden centers with overhead irrigation, hair salons, seafood markets, meat and deli markets, produce areas, dairy refrigerators and freezers, refrigerated display cases with heat recovery equipment, ice cream shops, banks, liquor stores, restaurants, public restrooms in the front or back, etc. This caused the number of master plan possibilities to multiply to thousands and thousands of options for configurations and sizes.
During the time we were working on all of these plan options, I sat across from an electrical engineer who I often teamed with for site-adapting the master plan drawings for a given project to make the record drawings for each store site. The site utilities were typically unique for each store site.
For the plumbing design, we had to obtain the site utility plan; figure out the size and capacity and elevation of the sanitary sewer and storm sewers; and direct all of the building drains toward the building sewers in order to meet the public sewer invert elevation—which added another level of design options to the master plans. There could be sewers leaving the store in the front, back, left or right side of the building, which meant all of the building drains needed to be revised to flow in a different direction with different building drain sizes based on the utility locations. Each orientation had to include all of the invert elevations of the building drains and sleeves through foundation footers, and invert elevations where drains crossed other utilities for each site, for each building storm and sanitary drain flow direction.
The water service could come from a different direction than the storm sewer or sanitary sewer, making four additional design options for the building water service supplies for the meter/backflow preventer and the fire pump room, (if a fire pump is required based on the water main hydrant test flow and residual pressure information). Consideration had to be given to combined or separate building water service pipes for the domestic and fire service, based on jurisdictional requirements. Some jurisdictions charged a significant water line user or initial tap fee, and the difference between a six-inch combined water tap and a three-inch tap, for domestic water only, could be hundreds of thousands of dollars in areas with water shortages.
In addition to these utility and floor plan variations, there were different plumbing codes in different jurisdictions, with different year versions of the code adopted for different jurisdictions. Some jurisdictions updated the codes every three years; other jurisdictions would make local amendments and adopt codes every six, nine, 12 or more years. All of these variations make for a multitude of plumbing design options. There are also many more design possibilities for unique store plumbing design options, when you consider storm drain sizing requirements based on the local rainfall rate.
My electrical design colleague, who sat across from me, could complete the electrical power and lighting design for a new store location in a few days, while the plumbing design seemed to always take a couple of weeks. This was because no matter where you go in the country, there is only one electrical code and the power distribution in the building was the same from the transformer location to the panel locations. For me, there were three model plumbing codes, and various states that have their own plumbing codes that may or may not be based on a model code, and many local cities or jurisdictions have their own plumbing codes or amendments to model codes.
Because of these different codes, we needed to redesign the plumbing to match the local code requirements every time a store was located in a different jurisdiction. For example, some jurisdictions wanted everything in the kitchens to flow through the grease interceptor. Other jurisdictions wanted only the wash sink of the three-compartment sink to flow through the grease interceptor. Still other jurisdictions required indirect wastes from all kitchen sinks, to prevent waste from backing up into the sinks; other areas allowed a floor drain or floor sink to be adjacent to direct-connected three-compartment sinks, to allow a backed up drain to spill onto the floor instead of backing up into a sink.
There are dozens and dozens of variations on kitchen grease waste designs. Some of the codes require food waste grinders from pre-wash sinks to bypass grease interceptors. Pre-wash sinks are a significant source of grease-laden waste. Other jurisdictions require a strainer between the food waste grinder and the grease interceptor. There are green designs that are discouraging food waste grinders because they waste electricity and they add solids to the grease waste drains—which can coagulate with congealing grease, and cause drain line backups and public sewer overflows.
Food waste grinders also increase the wastewater treatment loads on wastewater treatment plants. These green design initiatives are mandating food waste bins next to the dishwashing sinks for scraping food waste off the dishes in lieu of grinding up the waste and sending it down the drain. There are also EPA initiatives to reduce water flow in various fixtures, including pre-wash sprays. These low flows may not be enough flow volume to carry the solids down the drain, and less hot water flow allows the grease to cool and congeal faster in the kitchen drains.
The entire kitchen grease waste and kitchen plumbing is an area that needs to have an ad-hoc code committee look into standardizing the design, or determine which way is best and provide consistent code language in all the model codes throughout the country. Redesigning the plumbing for each municipality’s unique code requirements is wasteful and expensive. I would like to see the plumbing industry accept the idea of merging all the plumbing codes into one model plumbing code.
One plumbing code
About 10 or more years ago, there was a series of meetings to discuss the possibility of two of the largest model code organizations merging, to have one model plumbing code. This would have been a significant milestone in the history of the model codes, and the talks were very close to resulting in an agreement to merge into one model code. However, there were a few political hurdles that kept the merger from happening. There was talk of one organization controlling the plumbing code, and the other organization controlling the other codes in the family of building codes.
Talks fell apart when political issues emerged over which organization controlled the selection of plumbing code committee members, and the various organizations and interest groups that would have been represented on the plumbing code committee. There were discussions of one organization being the secretariat of the plumbing code separate from the other organization's model code process. This, along with a few other issues, became too much of a hurdle.
I would like to see a single model plumbing code with the help of an impartial group to facilitate a fair and balanced committee and process. I think the plumbing engineers are in a good position to help facilitate, or at least encourage, a single model plumbing code by inviting all three model code organizations and the various state code groups to join in serious talks about developing a single model plumbing code. The key is to keep the selection of code committee members to a balanced representation of the plumbing industry, where no single organization or group has more than 25 to 30 percent voting members.
I think it would also be a good idea to have a required plumbing science and engineering training class and a qualification exam for anyone considering serving on the plumbing code committee. Then everyone serving on the plumbing code committee would have a well-rounded foundation in plumbing science (not code language). A training course and an exam could be administered to code committee candidates to assure all code committee members have a minimum level of knowledge in all areas of the science of plumbing and the plumbing code language.
I think having an education program and qualification exam would help the plumbing code committee to follow good science, and prevent the plumbing code from violating the laws of physics.
Ron George, CPD, is president of Plumb-Tech Design & Consulting Services LLC. The offices of Ron George, CPD, have relocated to 303 N. Monroe Street, Monroe, Mich., 48162. The phone numbers and website will remain the same: Office 734-322-0225; Cell Phone: 755-1908; and Website: www.Plumb-TechLLC.com.