I think it is a bit more complicated than that to have your washing machine run off your waste water line. With the rate of flow alone, it may take your washing machine around a hour just to fill up with water, and that doesn't include the rinse cycle etc. You also would have to stand there and manually shut off the water line at the correct time to prevent overlow, unless you tried to plumb the waste line in through the cold water intake in the back of your machine (which I wouldn't recommend doing since you would have to create some sort of an adapter to attach to the water input in the machine).
The best use I could see is, get a faucet attachment to pull water from the COLD water supply on your washing machine to feed into your RO
unit, then use the attachment to tap into the water drain from your laundry system. That way you can utilize your existing plumbing in and out.
Some people store the waste water in a container and then use it to water plants etc.
To plumb water to the RO
unit, I personally used the self taping valve to attach to some copper tubing, I have not tried the ones that attach to faucets or the laundry unit.
For the price, that seems good, but you may want to look at thefilterguys.biz. They have great prices, great systems, and were extremely helpful. I got the Ocean +1 system with a booster pump and an additional addon stage, and love it.
For storage, I have the line attatched to an auto shuttoff valve in a 45 gallon garbage can. That way I can store enough water for a large water change. When it is time to mix the salt, I put the salt in a 5 gallon bucket, then pour RO
water into it to mix, then add it to my system.