Reverse Osmosis Saddle Drain on Brass (pic attached)

[MikeGA]

I'm going to be installing a reverse osmosis system in my sisters apartment. I've done this twice before on my house having PVC pipe and easily drilling a 1/4" hole and installing a saddle valve. However, she lives in an apartment building and PVC is not allowed, thus the brass drains.

Any ideas here on best to do this? I dont have enough of a horizontal drain to drill a hole and I'm wondering what size the tee is. I thinking of tying into the tee from the dishwasher drain.

Thoughts here?

 

[MikeGA]

I'm going to try this...
https://www.amazon.com/Watts-Premier-164020-Plumbing-Adapter/dp/B009XDMEK4

 

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[Reach4]

Is that small copper tubing going to the fridge? You should not run RO water through copper tubing. Maybe it would be OK if you remineralize it first. I am not sure.