Unusual standing water level in drain

[kaulbach]

Hello and thanks for taking the time to read this.

Background:

• Experienced remodeling contractor
• Remodeling a bathroom
• Slab foundation, first floor
• House is about 30 years old
• Client wants to change a regular shower to a curbless shower with a trough style drain
• The trough drain is approximately 48" long by 4" wide by 4" deep and is mounted above a pvc pan liner that is sloped to a shower drain with a flange for the liner.

Issue:
The standing water level in the pipe above the P-trap is only 3" below the floor surface. Usually in my area (Dallas) the P-trap and drain are installed deeper, and the standing water level is more than 6" below floor level.

If I install the trough drain, the bottom of it would be more than 3" below floor surface. The standing water level would always be in the trough basin, and also above where the shower pan liner enters the drain flange below the trough.

The drain is not clogged or backed up. There is a tub on the other side of the room, not directly connected to the shower drain, that has the same standing water level (3" down from the floor surface.)

Any ideas on why the water level is so high and how to get it lower?

 

[IFIXH20]

Have you actually put something in the drain to see how low the p-trap is below the floor level. You say the water level is 3'' below the floor, find out how low the trap is. There could be something wrong with the drain line creating a higher water level in the trap.

 

[kaulbach]

IFIXH20:

The outside bottom of the P-Trap is 8" below the floor surface. The top of the (nearly horizontal) drain line connected to the P-Trap is 1-1/2" below the floor.