Can I use water from a dehumidifier for my plants?

I've got a dehumidifier which we need to run in our old poorly insulated house. We sometimes get a gallon (or more) of water per day. It seems like a waste to poor it down the drain. It seems clean, I wouldn't drink it, but maybe I can water my plants with it? If so, is there something special I should do to treat it (like let it sit in a big barrel for a few days etc), or can I just use it?
I appreciate the help!

Drug stores and hardware stores sell water quality test kits for about $10. If the water is fit for human consumption, you are on the right track. I believe you also have a pH meter? The pH of a cup of water can vary by +1 or -1 depending how dirty the cup is. No bother. For the plants you are growing, you'd prefer a pH between about 6.5 and 7.0. If it is between 5.5 and 8, add some garden dirt first and let it sit.

Just for fun, check your tap water

Next, check some Diet Coke

Next some beer!