Up until around 1950, almost every bathtub had something called a drum trap installed beneath it. A drum trap is different than the typical P-trap that is seen under most fixtures today. The modern P-trap is named that because if you turn it on its side, it is shaped like the letter “P”. Drum traps are shaped like a drum and are about the size and shape of a two-pound coffee can.

Drum traps, like any other trap, are designed to hold water in them. The water in the trap makes a seal, and the seal prevents sewer gases from escaping into the house. In the early days, people were worried about the water evaporating out of the trap, so larger drum-shaped traps were installed. They held more water and had a larger water surface area, so the water would be less likely to evaporate.

Antiquated drum traps are commonly the reason for plugged tub drains that need to be unplugged. If a power snake is used to unplug it, a problem arises when the snake hits the area where the drum trap is located, and the pipes do not match up on both ends of the drum. The snake has nowhere to go. Also, if it is a lead drum trap, there is a chance of the power snake piercing the side of the lead drum trap.

Drum traps also tend to be difficult to take apart to clean out. Some of them come with a removable cover on either bottom or the top. Over time that cover gets corroded shut and welded into place. Often, in the process of trying to get that cover off it takes so much force that it twists the whole lead drum trap into a mess. St Paul Pipeworks plumbers recommend replacing existing drum traps with a more modern P-trap. The P-traps are designed to be easily taken apart, so if it ever does plug up, access isn’t hard to clean it out.

St Paul Pipeworks plumbers replace drum traps so often they always have the right materials stocked on their trucks. They have learned the common layouts that work to allow them to take out the old drum trap and get the new P-trap installed. It can be a bit tricky because there are often floor joists and other structural lumber in the way.

St Paul Pipeworks plumbers are used to working around existing structures when taking the whole lead assembly out. They go all the way back to the cast iron or galvanized steel pipe that the lead trap fastens to and make a cut where the lead ends. Then the plumber makes a transition to the new, heavy plastic ABS pipe and runs that pipe over to the bathtub installing the new P-trap in place.

Along the way, in the section between the old pipe to the bathtub waste, typically, there is also a vent pipe for the sewer gases to escape. It also needs to be joined to provide air to the whole system. Upon completion, the plumber will thoroughly test the trap to ensure all clogs are resolved and the new P-trap will drain much better than before.

If you are having trouble with a plugged-up bathtub drain or are just looking for a quality plumber in the St. Paul and Minneapolis metro area, give St Paul Pipeworks a call today.

Yours Truly,

Matthew Dettwiler

Social Media Manager


Q: What is the difference between a drum trap and a P-trap?

A: A drum trap and a P-trap are two types of plumbing traps used to prevent sewer gases from entering your living space. The main difference lies in their design and function. A drum trap is a cylindrical container with an inlet and outlet located on the sides, while a P-trap has a distinctive P-shaped bend in the pipe. The P-trap is more commonly used in modern plumbing systems due to its superior functionality and ease of maintenance.

Q: Which trap is more efficient at preventing clogs?

A: When it comes to preventing clogs, a P-trap is generally more efficient than a drum trap. The P-trap’s unique shape creates a water seal that helps prevent sewer gases from escaping while allowing water to flow freely through the pipe. Additionally, the P-trap’s curved design helps trap debris and prevents it from clogging the plumbing system. Drum traps, on the other hand, can be more prone to clogging due to their less efficient design.

Q: Are drum traps still used in modern plumbing systems?

A: While drum traps were commonly used in older plumbing systems, they are not typically installed in modern plumbing systems. Building codes and plumbing standards have shifted towards the use of P-traps due to their improved efficiency, ease of maintenance, and ability to prevent clogs. If you have a drum trap in your home, it is advisable to consult a professional plumber to evaluate its functionality and consider upgrading to a P-trap if necessary.

Q: Can a drum trap be replaced with a P-trap?

A: Yes, in most cases, a drum trap can be replaced with a P-trap. However, it is essential to consult a professional plumber to assess your specific plumbing setup and determine the feasibility of the replacement. The plumber will consider factors such as the pipe size, location, and overall plumbing system design to ensure a seamless transition from a drum trap to a P-trap.

Q: Are there any advantages to using a drum trap over a P-trap?

A: While P-traps are generally preferred in modern plumbing systems, there might be rare instances where a drum trap is necessary or advantageous. One advantage of a drum trap is its higher capacity for holding water, which can be useful in certain commercial or industrial applications. Additionally, some older buildings may have unique plumbing configurations that require the use of a drum trap. However, it is recommended to consult with a professional plumber to determine the most suitable trap for your specific plumbing needs.


What’s the difference between a Drum Trap and a P-Trap? Ask A Plumber…