clogged pipe or trap issue?

windowguy

my basement laundry room sink drain connects via a T to the vertical pipe that is the drain for my kitchen sink above. when i run my kitchen sink the water comes back up through the laundry room sink, and then eventually all goes down (slowly). I'm trying to figure out if the pipe under the slab is clogged (or built up) or is my trap under the laundry sink wrong.

The bottom of the trap is about 8 inches below the pipe that leads to the T to the main drain. If i make the trap HIGHER than the T it will stop the water from backing up into the laundry sink?

I know i can just put a check valve before the T to keep the water from backing up but i just thought i'd ask if there is a science to whether the sink trap should be higer or lower than where it T's into the main drain pipe.

Deep down i think the real problem is a clog way down-pipe but it's worth asking if my trap is wrong. So to picture it i have sink drain that drops 12 inches, then trap, then up 8 inches then horizontal to T to main drain. Water from upstairs sink instead of going straight down the pipe makes a left at the T and back up into my laundry sink. Would it only do that if below that somewhere it is clogged? or will water search out any T and travel down it (and then UP into my laundry sink).

THANKS!

Grampa Bud

You should have an 1/8 to a 1/4 bubble pitch from the outlet of your trap to the inlet at the "TEE", not from the bottom of your trap. You don't say what type of pipe you have for your drain line, galvanized or schedule 40 PVC, or castiron. You also don't mention if you have vented the laundry drain. "Wet" venting your drain is not a good idea for exactly the reason you mention about the drain backing up. Whether you are using PVC, or steel, or castiron your TEE should have a sweeping curve that runs from the branch inlet around to one end of the TEE and that end should be looking down towards the floor. If the TEE is correctly in place and the pipe has the correct pitch and vented properly both the kitchen and laundry will have no problem draining. Unless you have a partially plugged sewer line under the floor.

plumber Jim

The drain pipe after the tee were you sink hooks up is clogged. It must be just partly open and letting it drain back down over time. you needed it snaked.

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majakdragon

Best guess would be a partial clog in the drain the sink goes into. This is forcing water to backup into your basement laundry sink.

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