In 1921, President Warren Harding appointed a prominent civil engineer, Herbert Hoover, to the position of Secretary of Commerce. Hoover saw great potential in the United States, and he set out to provide proper planning direction in an effort to change the course of the nation.

The early 1920s was a time of prosperity in the United States. With the emergence from World War I and the wealth of the nation coming into prominence, the country was able to improve the quality of its citizens’ lives by applying better engineering concepts. Hoover wanted water and electricity in every home, as well as indoor plumbing. 

At the time Hoover was appointed commerce secretary, less than 1% of the homes in the United States included indoor plumbing. In 1921, Secretary of Commerce Hoover started the Building Material and Structures Division of the National Bureau of Standards (NBS), today it is known as the National Institute of Standards and Technology in Gaithersburg, Md.

Dr. Roy B. Hunter worked at the NBS; his job was to research and discover inexpensive ways to provide indoor plumbing for a safe, clean and healthy nation. Hunter’s plumbing research was a cornerstone in Hoover’s vision of bringing engineering to the Commerce Department. Hoover felt the Commerce Department should control the standardization effort, as this would improve the ability for entrepreneurs to obtain easy access to the marketplace. 

Standards for products were emerging at the same time as plumbing codes. The great conflagrations, or fires, on the mostly wooden structures in the east coast cities brought together many fire brigades and fire departments from near and far to fight fires in congested areas. They soon found their hoses could not be connected because each fire department had a different hose diameter and hose thread. 

Soon after the Great Baltimore Fire in 1904, a call was made to standardize fire hose threads and other critical products, such as bolt threads, so they could be consistent and compatible in different parts of the country. The Department of Commerce was already standardizing weights, measures and scales to ensure fair trade in commerce from one city to the next when it came to buying and selling grains and other bulk products.

Plumbing Research

Much of the original scientific research data collected on plumbing systems, fluid flow in pipes, and the probability of simultaneous fixture use was collected during tests conducted by Hunter in the 1920s through the 1950s. His research and testing allowed the Department of Commerce’s Building Materials and Structures (BMS) Division to develop and publish a series of three documents that, together, helped form the understanding of the basic fluids and hydraulic principles of modern-day plumbing. 

This series of documents was intended to give guidance for the construction of safe and inexpensive plumbing systems in federal projects. These documents became the basis for many of the sizing and pipe capacity charts and tables in our plumbing codes: 

BMS 65, Methods of Estimating Loads in Plumbing Systems (using fixture unit values established by Hunter based on the probability of simultaneous use of various plumbing fixtures)

BMS 66, Plumbing Manual 

BMS 79, Water-Distributing Systems for Buildings

In the BMS division paper, BMS 66 (1940), Hunter wrote: 

“The purpose of this series of papers is to collect, in an organized form, the mass of information obtained by the author over a number of years, beginning with the investigation of 1921 of plumbing of small dwellings, and including the current research (1937-1940) on plumbing for low-cost (multifamily) housing, together with the results of intervening experiments related to plumbing requirements, and to interpret the results of these investigations in a form suitable for direct and practical application. 

“It was hoped that this series of papers would supply the logical answer to many of the controversial questions pertaining to pipe sizes and design of plumbing construction.”

The three BMS documents served as the basis for every up-to-date plumbing code of the time. The federal government did not see it as its job to mandate and maintain a nationwide plumbing code, but it offered the BMS documents as suggested documents for local jurisdictions to adopt. 

During this period, the federal government was still of the opinion that construction projects should be regulated on the local level, and the plumbing code was only mandated for federal projects.

It was Hoover’s vision to develop these documents, and Hunter’s research was the key to the development of the first nationwide plumbing code. Through the efforts of the NBS, I used a later version of this code on many government military projects when I first started designing plumbing systems in the 1970s. Years later, I heard the earlier version was nicknamed the “Hoover Code” because it was developed under President Herbert Hoover’s administration. 

The foreword printed in the BMS 66, Plumbing Manual, said:

“This report has been prepared by a representative committee to serve as a guide for federal agencies that design, install, or approve plumbing. It is the product of a careful review of existing recommendations, supplemented by consideration of the results of experimental work at the bureau and by group discussion among the committee members. 

“The aim has been to inspire adequate and healthful plumbing at a minimum expense. It is hoped that the report will prove useful, not only for Federal plumbing work, but in connection with efforts to bring about greater uniformity in plumbing requirements and to reduce the cost of construction, of which plumbing forms a part.
— Lyman J. Briggs, Director, National Bureau of Standards”

Additionally, Hunter published a list of basic principles that needed to be followed to have a safe and affordable plumbing system. These basic principles were eventually included in an early version of the American National Standards Institute (ANSI) A40 Plumbing Standard, which included the basic principles for safe and economical plumbing. 

In 1940, another ANSI A40 committee was formed to create various reports using Hunter’s work. In 1949, the work received approval as being developed in an open consensus process, and it received ANSI accreditation. Shortly after the accreditation of the 1949 report, another A40 committee was formed. 

This committee’s work, known as the A-40.8-1955, was completed and published in 1955 and was, for many years, known as the National Plumbing Code. This code was used mostly in government projects. 

A 1929 document, titled “Recommended Minimum Requirements for Plumbing,” followed a similar theme, writing:

“In order to have good and economical plumbing, it is necessary that there should be some agreement on the rules governing its design and installation … Particular emphasis is placed upon its usefulness in connection with low-cost housing where there is special need to take advantage of legitimate economies. The field of the manual, however, is not restricted to housing, since the same fundamental (hydraulic) principles apply in any structure.”

1955 National Plumbing Code

The 1955 edition of the A40.8 document contained updated language and was primarily concerned with low-cost housing and providing the minimum necessary cost for the installation of plumbing that provided sanitation, increasing public health and safety. Included in the A40.8 was a list of 22 basic principles, which were intended to be guidelines for the later development of a national plumbing code. 

Failed efforts to update the 1955 ANSI A40.8 document during the 1960s led to the eventual development of the National Standard Plumbing Code. 

The basic principles listed in the 1955 edition of the ANSI A40.8 document are as follows:

• Principle No. 1: “All premises intended for human habitation, occupancy or use shall be provided with a supply of pure and wholesome water, neither connected with unsafe water supplies nor subject to the hazards of backflow or back siphonage.”

My comment: This principle recognized and addressed backflow and back-siphonage as a serious health and safety concern. Backflow prevention is covered in Chapter 6 of most model plumbing codes in the United States, which covers water supply and distribution. 

• Principle No. 2: “Plumbing fixtures, devices and appurtenances shall be supplied with water in sufficient volume and at pressures adequate to enable them to function satisfactorily and without undue noise under all normal conditions of use.”

My comment: Chapter 6, Water Supply and Distribution, of the U.S. model plumbing codes covers requirements for cold and hot water. It also covers sources of water, water quality, minimum flow and pressure, and maximum flow and pressure at each fixture. 

• Principle No. 3: “Plumbing shall be designed and adjusted to use the minimum quantity of water consistent with proper performance and cleaning.”

My comment: This was the original water conservation language. The Energy Policy Act of 1992 and subsequent revisions established maximum flows and consumption at various fixtures. Flows and consumptions are also covered in Chapter 6 of the model plumbing codes.

• Principle No. 4: “Devices for heating and storing water shall be so designed and installed as to prevent dangers from explosion through overheating.”

My comment: This was pre-cursor language to Chapter 5 code requirements for temperature and pressure-relief valves, and additional water heater requirements were added for water heater safety.

• Principle No. 5: “Every building having plumbing fixtures installed and intended for human habitation, occupancy or use on premises abutting on a street, alley or easement in which there is a public sewer shall have a connection with the sewer.”

My comment: This requires connection to public sewers in the street when sewers are present. Connection to the public sewer are covered in most model plumbing codes in Chapter 7, Sanitary Drainage.

• Principle No. 6: “Each family dwelling unit on premises abutting on a sewer or with a private sewage-disposal system shall have, at least, one water closet and one kitchen-type sink. It is further recommended that a lavatory and bathtub or shower shall be installed to meet the basic requirements of sanction and personal hygiene. 

“All other structures for human occupancy or use on premises abutting on a sewer or with a private sewage-disposal system shall have adequate sanitary facilities but in no case less than one water closet and one other fixture for cleaning purposes.”

My comment: This was to ensure adequate fixtures were in the building for toilet facilities and washing. This language has been replaced with model code language in Chapter 4, covering minimum fixture requirements for bathing, washing, health and hygiene.

• Principle No. 7: “Plumbing fixtures shall be made of smooth, nonabsorbent material, shall be free from concealed fouling surfaces, and shall be located in ventilated enclosures.”

My comment: This language for smooth fixture surfaces is intended to eliminate bacteria from growing on a fixture surface. This requirement is covered in the fixture standards referenced in Chapter 4 of the model codes. Many early fixtures were made of wood, which is not a nonabsorbent or impervious surface. The model mechanical codes cover toilet room ventilation.

• Principle No. 8: “The drainage system shall be designed, constructed and maintained so as to guard against fouling, deposit of solids and clogging, and with adequate cleanouts so arranged that the pipes may be readily cleaned.” 

My comment: Fixture traps and sanitary drainage piping cleanouts are covered in Chapter 10 of the model codes. Pipe sizing and minimum sanitary drainage pipe slope are covered in Chapter 7.

• Principle No. 9: “The piping of the plumbing system shall be of durable material, free from defective workmanship, and so designed and constructed as to give satisfactory service for its reasonable expected life.”

My comment: The approved pipe materials in the model codes for domestic water systems are covered in the section on materials in Chapter 6, Water Supply and Distribution. Sanitary drainage pipe materials are covered under the material section of Chapter 7. Storm drainage piping materials are covered under the material sections referenced in Chapter 11, Storm Drainage.

• Principle No. 10: “Each fixture directly connected to the drainage system shall be equipped with a water-seal trap.”

My comment: Fixture trap requirements are designed to prevent sewer gas from entering the building from the building sewer using a water seal in a trap or dip in the piping. Newer devices are available that meet the intent of this principle but are not covered in Chapter 10, Traps, Interceptors and Separators, of the model codes. The newer technologies allow waste to go down the drain but stop sewer gasses. 

These other types of installations include approved product standards, but the language is not in the codes. The installations are generally only used in engineered systems using the requirements in the alternative engineered systems in Chapter 3 of the model codes. 

• Principle No. 11: “The drainage system shall be designed to provide an adequate circulation of air in all pipes with no danger of siphonage, aspiration or forcing of trap seals under conditions of ordinary use.”

My comment: This provision addresses the need to limit the waste flow in the drain to a half-full flow so as not to cause pressure disturbances within the sanitary drainage piping systems. It also addresses the venting of fixture traps to prevent siphoning. Roof conductor piping does not need to limit flow because there are no traps or vents on storm drains. 

However, if there is a combined sewer with a house trap, additional venting ahead of the house trap may be needed to prevent sluggish flows. Venting is covered in Chapter 9 of the model codes.

• Principle No. 12: “Each vent terminal shall extend to the outer air and be so installed as to minimize the possibilities of clogging and the return of foul air to the building.”

My comment: Venting is covered in Chapter 9 of the model codes. However, newer venting methods are available for lesser installation costs and equivalent performance when installed in accordance with the manufacturer’s installation instructions with alternative engineered systems.

• Principle No. 13: “The plumbing system shall be subjected to such tests as will effectively disclose all leaks and defects in the work.”

My comment: Testing for each system is covered in Chapter 3, General Regulations of the model codes.

• Principle No. 14: “No substance which will clog the pipes, produce explosive mixtures, destroy the pipes or their joints, or interfere unduly with the sewage-disposal process shall be allowed to enter the building drainage system.”

My comment: The exclusion of materials detrimental to the sewer system is covered in the model codes under Chapter 3, General Regulations. 

• Principle No. 15: “Proper protection shall be provided to prevent contamination of food, water, sterile goods and similar materials by backflow of sewage. When necessary, the fixture, device or appliance shall be connected indirectly with the building drainage system.”

My comment: Flood hazard resistance is covered in the model codes in Chapter 3, General Regulations.

• Principle No. 16: “No water closet shall be located in a room or compartment which is not properly lighted and ventilated.”

My comment: This is a general building code requirement in some model codes and may vary in some jurisdictions. Generally, the model building codes reference the other codes and call for lighting lumens levels and ventilation. Lighting is covered in the electrical code. Ventilation is covered in the mechanical code.

• Principle No. 17: “If water closets or other plumbing fixtures are installed in buildings where there is no sewer within a reasonable distance, suitable provision shall be made for disposing of the building sewage by some accepted method of sewage treatment and disposal.”

My comment: Private sewage disposal in a private sewage treatment system or septic system is covered in some local and model private sewage disposal codes or by the local health department.

• Principle No. 18: “Where a plumbing drainage system may be subjected to backflow of sewage, suitable provision shall be made to prevent its overflow in the building.”

My comment: Backwater valves are recommended whenever there is the potential for sewage or stormwater backing up into and flooding the lower levels of a building. Choosing a quality backwater valve and having a preventative maintenance schedule for inspecting and cleaning the valve are important for proper operation.

• Principle No. 19: “Plumbing systems shall be maintained in a sanitary and serviceable condition.”

My comment: This is obvious, but providing a preventative maintenance schedule where drain lines are scoped for potential blockages, and routine cleaning of drains could prevent costly backups. With water conservation efforts, drain line transport of solids is limited. If there are long horizontal building drains and sewers, consider automatic or manual flushing valves to periodically flush moderate to large volumes of water down drains to clear them.

• Principle No. 20: “All plumbing fixtures shall be so installed with regard to spacing as to be reasonably accessible for their intended use.”

My comment: Fixture spacing and clearance dimensions are covered in building codes and in some model plumbing codes. The Americans with Disabilities Act also includes requirements for fixture spacing, mounting heights and clearances for accessibility.

• Principle No. 21: “Plumbing shall be installed with due regard to preservation of the strength of structural members and prevention of damage to walls and other surfaces through fixture usage.”

My comment: Cutting, drilling, notching, or other structural alterations are generally prohibited or limited and require the architect or structural engineer’s input. This is covered in Chapter 3 of the model codes.

• Principle No. 22: “Sewage or other waste from a plumbing system, which may be deleterious to surface or subsurface waters shall not be discharged into the ground or into any waterway unless it has first been rendered innocuous through subjection to some acceptable form of treatment.”

My comment: Chapter 10 of the model codes covers the requirements for traps, interceptors or separators.