The reverse osmosis installation instructions state

if you have garbage disposal then install the drain saddle before it

Unless I am misunderstanding what "before" (or after) means, it is unclear to me how I could ever install drain saddle before garbage disposal in my case as it looks like this:

enter image description here

Two questions:

  1. Does it mean I have to install drain saddle in dishwasher hose? Obviously it would not work on the ribbed hose.
  2. Alternatively, are there Reverse Osmosis faucets that would have two holes where second hole would simply drain directly in sink?

1 Answer 1


That video is confusing. The purpose of the drain saddle is to provide a channel for the RO system to drain excess water - this is pretty standard. The problem with the current drain configuration is that the disposal runs directly into the P trap. You actually want the drain saddle installed between the disposal and the P trap.
The proper setup for this is to rerun your 1.5 inch drain from the disposal running it horizontally far enough for you to attach the drain saddle and then into the P trap. You may be able to rotate the elbow coming out of the disposal to accomodate a horizontal run. If not you may have to rotate your disposal a few degrees to give you the room you'll need.
I'm not sure of the building codes in your area but I'm fairly certain that attaching it to the drain before the P trap would violate code.

  • I think no, the video shows the saddle connected before the trap.
    – Jasen
    Jan 19, 2021 at 5:12
  • My understanding is that the drain saddle installation location may prevent backflow contamination Jan 19, 2021 at 5:16
  • Yes. It has to be before the trap. The drain saddle does prevent backflow contamination but I believe all outflow from a residence must be protected by a trap.
    – HoneyDo
    Jan 19, 2021 at 5:19
  • @HoneyDo Did you mean to say that in drain saddle there is something like one way vent? Jan 19, 2021 at 6:01
  • @user389238- drain saddles are not the same as check valves. what HoneyDo is saying is the the trap protects any connected lines above it from sewer gases and possible contamination.
    – ojait
    Jan 19, 2021 at 14:19

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