Determine your size for freestanding bathtub

After remodeling the bathroom, it's usually very difficult to install the Freestanding Bathtub on the second floor because of the limited space (high of joist), but the Flex p-trap will help you. The Freestanding bathtub from Fig.54, Fig.55, Fig.56 and Fig.57 will help you to determine the size needed.

To install the p-trap with 2.0 inches water seal you need minimum 5.0 (1.5+2.0+1.5) inches of space under the tub, but the freestanding bathtub has only 3.5 inches; because of this, you have to cut the floor. However, Flex p-trap for Freestanding Bathtubs can be tested for water leaks without having to damage the sealing of the first floor: you can lift the tub on two 4x4 wood block, fill up the tub with water and check if it's the leaking by using your hand. When the Freestanding bathtub it is on the first floor, you already have access to the p-trap to check for leaks. The tolerance for measurement is ±0.5 inches.

  1. First, check the installation instructions of the freestanding tub.
  2. Second, check the space under the floor.
  3. Third, choose the right p-trap from the images below, and determine the dimensions from Fig.54-57 for installation.
  4. Forth, read the installation instructions of the flex p-trap for freestanding bathtubs.


Fig.54 Fig.55
 Fig.54 (video 54)   Fig.55 (video 55)


Every freestanding bathtub has a minimum space of 2.25-3.50 inches between the bottom of tub and the floor. The Flex p-trap for Freestanding Bathtub can be installed with the horizontal arm above the house floor and under the home floor. If you do not have enough space under the house floor, refer to Fig.54 or Fig 55. The best way to install the Flex P-trap is with the horizontal arm above the house floor and with the Marvin adapter in horizontal position (Fig 54). If you use the dimensions from Fig 54 the flex p-trap will have a length of 20 inches (product ID: Flex FB-trap/20”). For flex p-traps installed with the horizontal arm above the house floor and with the Marvin adapter in vertical position, use the 24 inches Flex Freestanding Bathtub (product ID: Flex FB-trap/24") - refer to Fig.55.


Fig.56 Fig.57
Fig.56 (video 56  Fig.57



If you have enough space under the house floor, you can use Fig.56 and the Flex P-trap for Freestanding Bathtub (22 inches, product ID: Flex FB-trap/22”). The flex p-trap for freestanding bathtubs can be cut to the exact length you need.

If you can't move the drain from the original position of the bathtub, refer to Fig.57 and use the extension tube (product ID: Flex FB-extension/24”). If your bathroom is on slabs and you can't cut the concrete, build one step around the freestanding tub and use the extension tube. You can install the flex p-trap for a freestanding tub with the faucet in the wall yourself, and check for water leaks manually.  To install a freestanding tube with the faucet in the tub, you can use a flexible hose for hot and cold water. The Flex BP-trap replaces the Shallow P-trap.