Subscribe to our newsletters & stay updated
This month, Plumbing Engineer magazine celebrates its 50th anniversary; the first issue was published in 1973. I have been writing for this magazine since 1994, and I wrote a column in the 25th anniversary issue in 1998. When I joined the plumbing industry in 1978 and started receiving the magazine in 1979, I learned much from the columnists before me.
When I started reading the magazine, it was within five years of the first publication. It included classroom articles to teach young designers and engineers plumbing, and standard details were shown with a write-up about them. Many plumbing design professionals had a binder of the standard details from Plumbing Engineer at their desks.
The magazine has changed ownership a couple of times and changed editors quite a few times, but it has always had the best magazine in the industry related to plumbing design and engineering. I hope to carry on the tradition of mentoring young designers and engineers.
Let’s look back at significant events over the last half-century since the first edition was published. Many advances have been made in plumbing since the early ’70s. Those were touted as the good old days, but we are generally much better off now than we were then. However, there is still room for improvement.
1973 Major News Events
• The United States ended its involvement in the Vietnam War after signing the Paris Peace Accords.
• OPEC oil production increased by 200%.
• After three years of gasoline prices at 36 cents/gallon, gas shot up to 39 cents/gallon.
• Secretariat became the first horse since Citation in 1948 to win the Triple Crown.
• The Alaska Oil Pipeline bill is passed to allow pipeline construction to access oil from the North Slope of Alaska. Alaska invested the money it received, and subsequent tipping and leasing fees allowed the Alaska Treasury to build to the point where interest on investments covers the state’s operating costs. Citizens in Alaska don’t pay taxes and receive checks from the state each year.
• The Supreme Court of the United States ruled on Roe v. Wade.
• The Cod War began in the United Kingdom and Iceland over fishing rights for codfish in the North Atlantic.
• The U.K. shortened the work week to three 10-hour days to give people more time off. This allowed busy companies to have two three-day work shifts for increased production.
• The Sydney Opera House opened.
• The Yom Kippur War and Oil Embargo caused oil prices to reach almost a dollar a gallon.
• The U.K. inflation rate was 8.4%, and the U.S. inflation rate was 6.16%.
• The American Society of Sanitary Engineering (ASSE) issued ASSE 1016 Standard, Individual Thermostatic, Pressure Balancing and Combination Control Valves for Bathing Facilities.
Of all the events listed, one of the most significant events was ASSE’s publication of an industry product standard that would eventually eliminate the risk of thermal shock and scalding, a common occurrence with older-style, two-handled shower valves.
Even though the standard was published, it was not adopted into the plumbing codes until more than a decade later when the plumbing codes finally added the requirement for all tub-shower valves to meet the ASSE standard.
America was prospering after World War II, with many Americans starting families, having children, buying homes, buying appliances and buying cars. Televisions only had a handful of stations to tune into, so the next day at work, it was easy to talk about TV shows and the news of the day. The Industrial Age was upon us, and manufacturing plants were churning out new products for homes and new cars.
In 1973, Walt Disney opened the largest theme park in the world, Disney World, near Orlando, Fla. President Nixon was in the middle of the Watergate Hotel break-in scandal, and the Apollo space program was regularly sending astronauts to the moon.
Those days were like the television programs “The Wonder Years” or “That ’70s Show.” We were carefree and enjoying new technologies such as color televisions, new cars, and modern homes within subdivisions, new water mains to provide clean water and new sewer mains to carry away and treat waste. Many new homes had modern plumbing, central heat and air-conditioning. All these things helped improve our health.
Later in 1973, the oil crisis was upon us, and the oil-producing states cut back on oil production to create shortages and drive the cost of fuel up. This made Americans conscious of energy costs, and conservation of energy became more important. Long lines were seen at gas stations, and gas prices increased. The big muscle cars fell out of favor for smaller, more efficient cars that served a more basic need of transportation — although we still have a love affair with trucks and big sport utility vehicles.
All these things were happening about the same time the first edition of Plumbing Engineer rolled off the presses.
Flow Rates Vs. Scald Risk
Let’s look at some of the changes in plumbing systems in the last 50 years. When the first issue of Plumbing Engineer magazine was published, most of our homes had dangerous, two-handled shower valves that did not compensate for pressure disturbances or temperature changes, so thermal shock and scalding were a higher risk than today.
There was no maximum shower flow rate in 1973, and some showers flowed up to 12 gallons/minute or more. As showerhead flow rates were reduced with voluntary energy and water conservation programs and later, with the federal Energy Policy Act of 1992 (EPAct92), the maximum allowable flow rates to many fixtures were established.
When EPAct92 was enacted, the maximum flow rates for plumbing fixtures became a matter of federal law (effective in 1994 for residential plumbing fixtures and in 1996 for commercial plumbing fixtures). However, this caused a scald risk problem.
When the flow rate to an old-style, two-handled shower head is reduced by simply installing a lower-flow showerhead on the shower arm, it increases the risk of thermal shock and scalding. The path of least resistance is no longer out of the showerhead; instead, the path of least resistance is now to another water-flowing fixture.
The water flowing to a nearby fixture can allow hot or cold water to cross over into the two-handled shower valve body during a shower. When cold water is used elsewhere in the building, the pressure drops in the cold water pipe, allowing the higher-pressure hot water to cross over into the cold water piping within the two-handled shower valve body when both valves are open and a flow restrictor is installed in the showerhead.
These older two-handled shower valves increase the risk of thermal shock and scald injuries when sudden changes in temperature can startle or thermally shock someone in the shower, causing slip and fall injuries. If someone slips and falls in a wet, soapy shower and is incapacitated for a period when the hot water temperature spikes, a thermal shock or slip-and-fall injury can turn into a scald injury.
This was realized by fixture manufacturers before the early 1970s. It is why ASSE developed Standard 1016 for pressure-balancing-type shower valves, thermostatic-type shower valves, and combination pressure-balancing/thermostatic-type shower valves with maximum temperature limit-stops and integral check valves to prevent crossover flow.
In 1973, ASSE issued ASSE 1016 to compensate for sudden temperature changes associated with pressure disturbances. In addition, and most importantly, ASSE 1016 required a maximum temperature limit-stop adjustment that provided scald protection with the ability to limit the maximum temperature flowing from a shower to a safe temperature (a maximum of 120 F, per the plumbing code).
The language requires the shower or tub-shower valve to have the ability to be adjusted to a safe temperature; the installer or the owner must adjust the limit-stop after the water heater has been fired up and cycled; that is, allowing it to reach its full hot water temperature. With the old, two-handled shower valves, thermal shock would be experienced when someone was in a shower with a two-handled control and someone else in the house flushed or used cold water while the person in the shower adjusted the water to a comfortable temperature.
Modern codes require showers and tub-shower fixture fittings to include pressure- or temperature-compensating valves conforming to the newest version of ASSE 1016: ASSE 1016/ASME A112.1016/CSA B125.16 - 2017(R2021) Performance Requirements for Automatic Compensating Valves for Individual Showers.
In 1973, there were little or no backflow prevention requirements for residential domestic water services. Backflow preventer manufacturers have done a good job of educating the industry about the need for them at the building service entrances for containment and protection of the public water main and at each individual fixture or point-of-use for isolation of each backflow hazard, with the correct type of device for the given hazard.
Today, the model plumbing codes have been revised to address requirements for backflow prevention. Many new backflow prevention devices protect us from the unseen hazards of cross-connection, such as dual-check backflow prevention assemblies, pressure vacuum breakers, reduced pressure backflow preventers with alarms and spill-proof backflow preventers.
Piping insulation evolved from asbestos, fiberglass and calcium silicate to many choices, including fiberglass, calcium silicate, foam glass, foam rubber and foam plastic, to name a few.
Hot water circulating systems were designed to be more efficient. In the last 50 years, several manufacturers have introduced domestic hot water temperature maintenance cables and thermostatic balancing valves. These cables maintain the water at a desired temperature if the insulation requirements are met in lieu of a circulating domestic hot water system.
Fifty years ago, it was not uncommon to see new homes and buildings built with galvanized water piping systems. Many of those piping systems installed in harsh water environments have been or are being replaced with other materials today; in a few locations, galvanized pipe remains.
As of this writing, galvanized steel pipe is still an approved potable water pipe material, but I can’t think of a good reason why it is still allowed. We have materials that perform just as well and are lighter, less expensive, less corrosive and less conducive to promoting bacterial growth.
Large or oversized water mains are still being installed or are in place. Recently, the awareness of bacteria in stagnant water pipe has led to a flurry of disinfection efforts by untrained individuals that have been destroying piping systems with hyperchlorination.
Currently, the codes address minimum levels of water treatment chemicals for disinfection but no maximums. There should be a maximum parts-per-million level of chlorine for each pipe material based on the piping material manufacturer’s recommendations, and contact times for disinfection should be adjusted accordingly. The fixture unit tables in the codes are being updated, but the existing oversized pipes will likely remain.
In 1973, copper was becoming more popular, and the use of the mechanical brazed-joint joining method became popular as it eliminated the purchase of fittings and minimized soldering/brazing time. Over the last 50 years, many new piping materials have been developed, such as chlorinated polyvinyl chloride (CPVC) and cross-linked polyethylene (PEX) tubing, PEX-AL-PEX, polypropylene, and many variations of composite pipe materials.
PEX tubing was not allowed in the United States until it was added to the mechanical codes in the 1980s for hydronic tubing in floors. In the 1990s, PEX was added as a domestic water pipe material in the model plumbing codes for domestic water distribution systems.
In the last 50 years, CPVC in copper tube size and PEX tubing have become more popular in residential and light commercial plumbing systems as less-expensive alternatives to copper. In the early 2000s, stainless-steel tubing was added to the plumbing codes for water distribution piping and, shortly thereafter, a flurry of buildings had high copper levels. This is because, in buildings with stainless-steel pipe connected to copper pipe, copper is less noble than stainless steel and will corrode or oxidize into the water.
CPVC Schedule 80 has become more popular recently because it is a material that is more resistant to water treatment chemicals such as chlorine and monochloramine that are now being used to disinfect building water distribution systems.
In 1973, PVC plastic piping was still fighting an uphill battle in the codes. Today, PVC drainage waste and vent piping is very popular in residential, light commercial and underground plumbing drainage systems.
Also in 1973, cast-iron hub and spigot piping with lead and oakum joints were still used on a regular basis in many areas of the country. Hub and spigot cast-iron drains with lead joints required more labor, including an intensive process to melt and pour lead during the installation process. Today, hub and spigot piping with push-on neoprene joints and hubless cast-iron piping are popular lately.
Those debates subsided as plumbers learned about the dangers and health effects of working with lead. Cast-iron piping with several new joining methods remains the best choice for a quiet and high-quality sanitary waste and vent system.
Water Conservation and Treatment
Recent water conservation efforts resulted in lower flows at fixtures, meaning water takes up to about five times longer to get from the water treatment plant to the end fixture. These slow flows have caused the dissipation of water treatment chemicals in the domestic water delivered from the water utility to levels that cannot control bacteria growth.
The water conservation programs led to water aging in the water mains and in building water distribution systems, leading to the growth of bacteria and microorganisms.
I have advocated for abandoning the water mains we currently use that share fire hydrants, and installing new, smaller water mains dedicated to potable water distribution while letting the old water mains serve only fire hydrants. We could also look at circulating the water mains back through the water treatment plants to retreat or polish the water to maintain water treatment chemical residuals at the ends of water distribution systems.
In some cases, the lack of water treatment chemicals in the supply water has been addressed by adding secondary or on-site water treatment systems at building water service entrances. Most of these secondary water treatment chemicals use oxidizing chemicals (chlorine, monochloramine, chlorine dioxide and ozone). These chemicals cause corrosion to metallic pipe and oxidation damage and deterioration to many plastic piping systems.
However, CPVC, which includes chlorine in its molecular structure, is not affected as much as other piping systems by these oxidizing water treatment chemicals.
Some of the most recent technologies have received resistance from trade unions because they are seen as reducing the need for pipe materials and labor. Controversial products include the air admittance valve, positive air pressure attenuators, and sanitary waste valves, among others. Many of these products include code limitations, but they have been successfully used by engineers around the country in alternative engineered systems.
I suspect the air admittance valves and other new technologies will become more appealing as larger projects realize significant savings when using these products as alternative engineered systems in accordance with the alternative materials sections of the model codes.
The last 50 years have seen a lot of changes; there will undoubtedly be more changes coming. One thing is for sure: Every month, when Plumbing Engineer arrives, I will read it from cover to cover to see what is happening in the plumbing engineering industry.