Is something coming to replace the P-trap? Time will tell.

One of the first things you learn in the plumbing profession is that the trap is sacred. This small U-bend device, or P-trap, if you prefer, provides a level of protection that makes the plumbing system safe and sanitary.

I was taught that you don’t screw with a trap. Furthermore, you make sure you always install the trap correctly. Otherwise, disease, odor, bacteria - you name it - will escape into a building. That is what every plumbing contractor is taught.

A trap is so important that we have requirements for trap seal primers for fixtures that have minimal use. We don’t want the trap to dry out.

Short History: The first plumbing was outdoors. We still have outhouses remaining in parts of the country. This was true throughout the world. When the plumbing is outdoors, there is no trap. When you sit on a seat in the outdoors, you have direct communication to the soil and waste. Of course, using an outhouse is not-too-pleasant a time.

For portable toilets, found at jobsites, campgrounds and parks, you also have direct communication to the soil and waste. There are no traps utilized.

When plumbing was first brought indoors, in the modern era, there were no traps. Of course, the room stank. That actually delayed the further introduction of indoor plumbing. Someone finally came up with the concept of a water seal trap. By placing this water seal trap in the fixtures, the odor was contained in the piping system.

The original idea of a trap was to seal off the odor. The odor was to stay in the piping system, and the indoor air would remain pleasant to breathe.

There were no concerns with disease or sanitation at the time the trap was introduced. The only concern was to keep the stink in the pipe and out of the building.

From an engineering perspective, a trap really screws up the flow of drainage in the piping system. It requires substantially more energy to have water pass through a trap than it does to simply run down a horizontal drain.

More than a hundred years ago, we settled on a 2-inch trap seal. The 2-inch trap seal was more than was required, since there was the possibility of losing part of the trap seal. The actual minimum requirement is a 1 1/2-inch trap seal. That is why the plumbing codes require the trap not be exposed to pressures exceeding plus or minus 1 inch of a water column. When exposed to these pressures, you still have 1 1/2 inches of a seal remaining.

Some claim that the real minimum required is 1 inch of a water seal. Another area of debate.

But most experts cannot agree why the minimum trap seal is required. The best explanation I have heard is that the minimum trap seal is based on sewer gas bubbling out. If you have 1 to 1 1/2 inches of water, sewer gas will not bubble through and escape into the breathing atmosphere.

What we have learned is that the trap does a lot more than simply keep the odor out of the building. We have learned that the odor also contains contaminants. Some of these contaminants can do harm to humans if exposed in large concentrations. The trap also blocks biological aerosols. These nasty items can cause disease.

So it only seemed appropriate that we maintained the concept that traps are sacred.

Times Are Changing: It appears that outside North America, traps are not that sacred. Water seal traps are not always used in England or Australia. The ideas from those countries are making their way into North America.

No, there have not been any changes to the plumbing code, nor are any currently proposed. The first step in this area is to develop new standards. IAPMO has a process whereby a manufacturer can develop an interim guide criteria or IGC standard. This provides an opportunity for a manufacturer to introduce new plumbing products quickly to the marketplace.

Over the past few months, IAPMO has developed IGCs to regulate devices designed to replace the water seal trap. One device is for nonwater-supplied urinals. Rather than a trap, there is an elastomeric membrane that separates the sewage from the indoor air. The membrane distorts to allow the urine to run down the drain, and then it reshapes to seal off the opening.

The other device is a long tube with an elastomer on the inside. The elastomer has a memory that results in the two sides closing off the opening. When water and waste are introduced into the piping, the elastomer opens, allowing the flow down the drain. When the flow is completed, the elastomer closes the opening. Some refer to this device as a trapless trap.

To be equivalent to a water trap seal, you need to have testing that establishes that equivalency. That is the purpose of the standard. However, how do you test for equivalency to a water seal?

Being from the old school, I was immediately alarmed when I heard that these products were going to be introduced into North America. I was familiar with the products in England and Australia. I was just hoping they’d stay in those countries.

But, being open-minded, I have to recognize that possibly something could be equivalent to a water trap seal. However, in my opinion, the testing needs to be very extensive. It just can’t be an elastomeric seal that opens and closes when water runs through it with the hope that it will last a lifetime. We need to test for that lifetime. We also need to test for what really goes down a drain. I have not seen any test protocol that makes me feel comfortable with these products. But I will stay open-minded.

So, if you encounter any of these trap substitutes, my suggestion is to do the same as I have done. Ask how they can test to show equivalency to a water trap seal. Scrutinize the testing very carefully. But keep an open mind.