I want to put in a reverse osmosis kit under my kitchen sink, and it requires a waste line tied into the main drain line of the kitchen sink. There's already a dishwasher drain line hooked up to the main drain line as seen in the picture:

enter image description here

I see there are drain line adapters I could buy which would allow me to connect my RO quick-connect and dishwasher to the same drain point:


but I'm not sure if the adapter will fit with the copper drain line that's already hooked up. It looks like a 1/2" copper pipe. Anyone know if this adapter will be compatible?


  • My RO system came with everything. I drilled a hole in the drain, inserted the tube and put the clamp over it. All done.
    – Jeff Cates
    Feb 6 '17 at 1:41
  • Hi yeah I just didn't want to drill a hole into the current waste line, I'm just paranoid that I won't do it correctly and I'll have a leak. Feb 12 '17 at 21:05
  • The hole will be at the top of the drain line. If sealed correctly with the saddle seal, no leak should occur.
    – Jeff Cates
    Feb 13 '17 at 2:28

That short piece of black rubber hose (with 2 hose clamps) that is included with the adapter in your link should attach directly to the copper pipe. Then you clamp your dishwasher hose to the proper size barbed tube; the RO drain uses the quick disconnect.

If the black hose is too big, use an adapter:

enter image description here

You should know that your dishwasher drain should be equipped with an air gap, or at least put an anti-siphon loop in there:

enter image description here

diagram stolen shamelessly from the web

  • Hi, yeah it turns out the black rubber hose is too big for the copper pipe. You mentioned the "adapter" that I could use to reduce its size so it'll fit the copper pipe. Does that have a name I could tell someone at a hardware store, or "black rubber hose adapter" is what I tell them? Thanks Feb 12 '17 at 21:04

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.