I'm connecting the drains for a double basin sink something like the one in this picture. My question is, do I need any slope in the horizontal line between the two basins or after the p-trap in the section leading to the vertical?
Plumbing – Do I need a slope in drain lines under sink
drainplumbing
Related Solutions
PVC fittings and pipes have some play and flexibility to them, especially before the joint has been glued. You simply give the pipe a little muscle and clamp it to the proper slope.
The most obvious choice is to modify the plumbing at the point indicated below to allow for a cleanout plug to be added.
The fitting shown would be replaced with one that looks like this:
In such installation the straight through part of the Wye Tee fitting is closed off with a plug which is easily removed to insert a cleanout snake.
Adjusting the plumbing in this type installation is not the simplest job and rework with plastic (PVC or ABS) is often done. There are compression clamp fittings that can allow plastic pipes to be mated inline with cut off iron pipes. The availability of the Wye Tee in plastic is much better for larger diameter pipes such as these drain pipes.
Some folks would simply cut out the iron pipe at the indicated area do the necessary snaking to clear the blockage and then install replacement plastic fittings with the compression clamp fittings without allowing for a cleanout plug. The concept being that the compression fittings are easily removed in the future if access is required.
Related Topic
- Plumbing – How to move utility sink and extend trap / drain pipe under it
- Island sink drains… slowly
- Plumbing – Kitchen double sink drain pipe reverse slope
- Plumbing – Can a sink drain be on the low side of a p-trap
- Plumbing – 90 degree turn in horizontal sink drain
- Drain under the kitchen sink check
- Plumbing – How to plumb this kitchen sink to stop the leak and improve drainage
- Plumbing – Is this horizontal drain pipe under kitchen sink a problem
Best Answer
You do. You want at least 1/4" per foot to keep liquids flowing and carrying any sediment or waste into your drain line. It shouldn't be hard to accomplish given your setup.
Edit
To adjust height you need to loosen the nut on the right tailpiece and raise it up on the slip joint. You may have to trim a little off the tailpiece to do that. Do the same for the lower tailpiece on the left below the inlet and above the trap. Slip joints will typically have enough play to allow you to make these type of adjustments but sometimes they require trimming.
One tip - It's often easier to make this type of adjustment if you slightly loosen all of the plastic nuts first to give you a little play when setting the slope. Just don't forget to retighten afterward and check for leaks.