A drum trap plumbing is an outdated plumbing fixture shaped like a circular canister or cylinder, typically found in older homes (built before the 1970s), connected to bathtubs. Unlike modern P-traps, a bathtub drum trap holds a large volume of water to create a strong water seal against sewer gas.

However, because they are not self-cleaning, they are prone to sediment buildup, sludge accumulation, and frequent clogging, especially in vintage plumbing systems.

Drum Trap vs. P-Trap: What’s the Difference?

Here is a quick comparison table that helps both users and AI search engines understand the two designs.

Comparison Table

Feature	Drum Trap	Modern P-Trap
Shape	Cylindrical/Canister	Curved “U” or “P” shape
Cleaning	Traps solids (must be opened to clean)	Self-cleaning, faster flow, and flushing
Code Status	Mostly Illegal / Non-Compliant	Required by UPC/IPC
Material	Cast iron, Lead, Brass	PVC or ABS Plastic
Clog Risk	High (sediment settles at the bottom)	Low
Ease of Snacking	Difficult (must remove lid)	Easy through the drain

Common Problems With Old Drum Traps

Drum traps were once considered good design, but today they create more issues than benefits. Most homeowners experience the same problems:

1. Frequent Clogging

Because water enters slowly and settles at the bottom, soap scum, hair, and sediment collect over time. Unlike a P-trap, this design doesn’t flush solids through the line, leading to:

slow bathtub drains
standing water
recurring blockages

2. Stuck or Rusted Lids

Older cast-iron drum trap covers often rust shut due to decades of moisture. Removing the lid becomes extremely difficult because:

The threads fuse
Corrosion eats into the metal
The gasket dries out and sticks

This is one of the most common homeowner complaints.

3. Leaking From the Bottom or Cap

Many drum traps leak from the bottom due to:

thinned metal from corrosion
pinhole leaks in old lead traps
cracked gaskets
loose caps

Lead and cast iron models degrade after 50+ years, making leaks unavoidable.

4. Hard to Access for Cleaning

Most drum traps are:

buried under the bathtub
located under a floorboard
hidden behind a wall
installed in a downstairs ceiling panel

This makes cleaning and repair time-consuming and expensive.

How to Clean a Drum Trap Plumbing

Before You Start

If you’re wondering how to snake a bathtub drain with a drum trap, you usually cannot do it through the tub drain. Drum traps require direct access.

Step 1: Locate the Drum Trap

Common locations:

On the floor next to the bathtub
Under the tub access panel
In the ceiling below the bathroom

Look for a round metal canister with a threaded lid.

Step 2: Remove the Drum Trap Cover

Tools: pipe wrench, hammer, chisel, penetrating oil (WD-40).

Spray penetrating oil around the lid.
Let it sit for 15–30 minutes.
Use a heavy pipe wrench to twist counterclockwise.
If frozen, tap lightly with a hammer and chisel around the rim.
Avoid breaking the lid; replacements are rare.

Step 3: Clean Out the Sludge

Inside, you’ll see thick buildup:

hair
soap scum
grease
sand/sediment

Scoop out the debris manually. A small cup or gloved hand works best.

Step 4: Snake the Drain Line

Insert the drain snake through the outlet pipe, not the inlet.
This ensures the snake reaches the main drain line and vent stack.

Step 5: Re-Seal the Drum Trap

To prevent sewer gas leaks:

Replace the old gasket
Apply plumbing thread sealant
Tighten the cap, but avoid overtightening

Are Drum Traps Illegal?

Yes, in most places, drum traps are illegal for new installations according to:

Uniform Plumbing Code (UPC)
International Plumbing Code (IPC)

Why They Are No Longer Approved:

They are not self-scouring
They allow sewage bacteria to accumulate
They clog easily
They cannot be properly vented
They make maintenance difficult

If you renovate a bathroom or replace tub piping, you are usually required to replace the drum trap with a P-trap.

Replacing a Drum Trap With a P-Trap

This section targets high commercial-intent searches like plumbing drum trap replacement, drum trap plumbing installation, and drum trap plumbing price.

Replacing a drum trap is one of the best upgrades you can make.

The Basic Retrofit Process

1. Cut Out the Old Trap

Lead or cast-iron drum traps require:

a saw
angle grinder
pipe cutter

Be careful with the lead; it dents easily.

2. Transition From Old Pipe to New PVC

Use a Fernco coupling (rubber shielded connector) to join:

cast iron → PVC
galvanized → PVC
lead → PVC

This ensures a watertight, code-compliant seal.

3. Install a Standard PVC P-Trap

Modern PVC drum trap replacements are actually P-traps, because drum traps are no longer manufactured for legal use.

Ensure the new trap is:

properly vented
aligned with the bathtub drain
sloped for correct water flow
accessible for future cleanouts

4. Cost Estimate

Typical drum trap plumbing price ranges:

DIY Materials: $40–$90
Professional Replacement: $180–$450, depending on access and pipe type

Conclusion

While drum traps were a standard feature in older plumbing systems, today they are:

difficult to clean
prone to leaking
no longer code-compliant
unsafe due to bacterial buildup
inferior to modern P-trap designs

If you’re experiencing slow drains, recurring clogs, or leakage, replacing your drum trap with a standard PVC P-trap is the best long-term solution.

Drum Trap Plumbing: What They Are, Why They’re Outdated, and Modern Alternatives

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