Yes, you can use a 2-inch P-trap on a bathtub. In fact, standard plumbing code allows you to increase a fixture drain and trap size by one size larger than the fixture outlet.
The standard bathtub P-trap size is 𝟏𝟏𝟐 inches in both nominal diameter and pipe size. This dimension perfectly matches the drain and overflow pipes that come standard with almost all domestic bathtubs.
US code basics for tub drains
Many jurisdictions require a minimum 1.5-inch trap and fixture drain for bathtubs. Overflows typically match at 1.5 inches.
1-1/2" Low Profile p Trap Tub Fitting: It is also suitable for RV bathtubs, it can bend and stretch freely in the narrow space of the bathroom without taking up your space.
Installing a freestanding tub and need a drain that fits in tight spaces? This low-profile P-trap is designed exactly for that. It's only 1 1/2 inches in diameter, and the flexible ABS pipe can stretch from 11 inches to 29 inches, so you can bend and route it around obstacles under the tub.
1.5-inch: This is the standard drain size for most home tubs, including alcove tubs, freestanding tubs, and clawfoot tubs. These types of drains allow water to drain smoothly from your home. 2-inch: This drain size is common in larger, higher-volume tubs, such as Jacuzzis, soaking tubs, and whirlpool tubs.
P-traps come in two standard sizes: 1 ¼ inches for bathroom sinks or 1 ½ inches for kitchen sinks. Larger sizes—up to 2 inches in diameter—are reserved for showers and toilets. In some rare instances, you may have a larger bathroom sink P-trap size, but it's not the norm.
Yes, bathtubs have P-traps. The P-trap (a U-shaped pipe under or just outside the tub) holds a small amount of water to create a seal that stops dangerous sewer gases from entering your bathroom.
It was my understanding that a typical kitchen drain used 1-1/2 inch and a typical bathroom sink used 1-1/4 inch. And at Home Depot they had the kitchen stuff together, and everything was 1-1/2 inch. And they had the bathroom stuff together, and everything was 1-1/4 inch.
The standard bathtub drain size for most residential tubs is 1.5 inches (1 1/2") in diameter.
In plumbing, the "135-degree rule" is a code standard that dictates how much a horizontal drain pipe can bend or change direction. It limits the total cumulative angle of pipe fittings before a system requires an access point (cleanout) or must be vented, ensuring proper flow and preventing chronic clogs.
Here are the top 5 common errors people make when installing baths:
For a standard shower-only pan, modern plumbing codes typically require a 2-inch drain. A 1.5-inch drain only handles about 8.3 gallons per minute and is strictly for tubs or very low-flow showers. Using 2 inches helps prevent flooding.
Most municipalities REQUIRE 2” trap for shower only! There is a real big / good reason for this. A tub can store/hold many gallons of water to compensate for slow drain ( not clogged completely) but a shower pan can not.
The standard tub drain size is 1 ½ inches—this is the nominal pipe size and the name you'll find on the shelf in the hardware store.
A P-trap is a small but essential component of your plumbing system. It's the curvy part of the pipe under the sink, bathtub, shower or any other drain in your home.
A Cinderella tub is a vintage, space-saving corner bathtub popular from the 1930s to the 1950s. It is designed to fit diagonally into a corner, featuring a wide, rounded front and built-in seating on the sides. These cast-iron, often colorful (pink, blue, yellow) tubs maximize functionality in small bathrooms.
A P-trap is the standard type of trap used for a bathtub, designed to create a water seal that prevents sewer gases from entering the home. Modern bathtubs utilize a 1-1/2 inch P-trap, while older homes might still use a cylindrical "drum trap".
In such cases, the water in the trap may siphon out due to inadequate venting, breaking the water seal.
The standard P-trap size for a shower is 2 inches. This diameter accommodates the rapid flow rate of standard shower heads and is the most widely accepted size under modern building codes.
Most standard bathtubs have a drain opening of about 1.5 to 2 inches in diameter, but it's important to measure precisely, as some older or custom tubs may have non-standard sizes.
The industry standard size for a bathtub trap (P-trap) is 𝟏𝟏𝟐 inches in both diameter and pipe connection. While the drain pipe leading into the trap is also 112 inches, the larger drain line in the wall leading away from the trap is typically 2 inches.
The standard drain pipe size for most residential bathtubs is 𝟏𝟏𝟐 inches. This applies to both the waste pipe (the shoe) and the overflow pipe, which meet at a tee and connect to the P-trap.