Please see attached picture. I used a combination of flex and fixed pipes under the kitchen sink. Please note that the level of U or P-trap is higher than the drain in the wall. Is this configuration or installation causing slow drainage and backup the water in the sink or there is some other issue?

How can I fix it? I am thinking of extending the vertical pipe so that level of p-trap comes below the drain in the wall. Would that fix the issue?

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1 Answer 1


Flex pipe is a disaster that usually doesn't wait long to happen. What you have now constitutes an S-trap.

The outlet of the P-trap should be slightly above the drain entry in the wall. About a 2% slope (1/4 inch per foot, or 2 cm/m.) Then a rigid pipe should connect the two points, typically with a slip fit connection to make the length adjustable.

Whether that is all the problems with the drain is unknowable, but those parts should certainly be addressed. If the pipe in the wall lacks a proper vent pipe going up, a Mechanical Vent also known as an Air Admittance Valve might help with a slow drain. If there is a clog in the drain pipe in the wall, that will have to be cleared.

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