exactly, is there a ydi button for the neighbor?

What I don't understand is why maintenance won't help until his neighbor calls. The OP sink is leaking, and the OP called maintenance to report that the neighbor noticed leaking coming from the OP apartment. Let me repeat the OP sink is leaking, not the neighbors sink is leaking, the OP SINK is LEAKING. Why would maintenance NOT help when the OP sink is leaking. The neighbor is just the one who noticed it first, and the OP is the one reporting that his own sink is leaking. Their maintenance must be stupid.

They probably need to be able to get into the neighbors in order to fix it properly since that's where the leak is going. Without his cooperation it may not matter what they do in the OP's place. It's also possible that the OP can't actually see the leak, since it had to be pointed out to them, and they need the neighbor to confirm that the leak actually exists. If the OP can't see the leak, it's possible that the neighbor is just screwing with them and there is actually no leak. If the neighbor is the type to pull those kind of pranks or to cause trouble they may just want it on record that specific neighbor had a complaint. I had a neighbors bathtub leak into my apartment once and they needed both of us to call and confirm that it was happening and to be home and available at the same time to repair the problem.

yes they must be able to get in to the neighbors apartment and they may not enter unless they have permission unless I believe it is an extreme emergency. if the neighbor won't call must not be that big of a deal.

#85, laws vary from state to state and country to country. I live in Oklahoma, and whether you live in an apartment or rent a house all the landlord (or maintenance person) has to do is give a one-day notice that they're coming in for a maintenance related cause and consent is implied. The tenant is allowed to say "no you can't come in" and the landlord has to work with the tenant to find an agreeable time. The landlord can get in trouble for going in after the tenant refuses to allow him/her in, but the tenant can also get in trouble for consistently refusing to allow the landlord in if the landlord has a good reason to be in there.

step it up, leave showers sink toilets and all running and WATCH THE FLOOD! (I am not liable to anyone or anything harmed by this poor choice subject to terms and conditions)

#47, the best part about that is getting your water bill. So while you might get some of the neighbor's things wet, you're the one ultimately paying the price :-)

55- not necessarily. Where I live, at least, water is almost always included in your rent. So the cost of the water bill wouldn't actually be an issue.

55 revenge has NO PRICE! (twirls mustache)

I agree. I'd jot down the date, time and name of the person you called in maintenance so if they try to lie and say they never got a call, you have the details that you did and was told your neighbor had to make the call

I totally agree - find out what laws there are about recording conversations. In some places you only need the permission of one party (so that can be you!) to record the conversation. If you need your landlords permission I'm sure he'd give it just to record that you called him about a specific matter at a specific time and date. "Hello Mr/Mrs. _____. It is Thursday, March 5, 2015 at 8:42 am and I am calling to inform you that my sink is leaking into the apartment directly below mine."