Absolutely every single abb stay ever should be considered that it may not happen (private service, with one listing and that host could die, quit, run away....). And if this is the only stay in the location that will fit your group or your budget then you have to go into it knowing that you could potentially have a problem.
And finally, if an abb space has a significant problem, then, it seems to me, that you have exactly 2 options: grab your bags, turn around and walk out the door citing that the place is unusable OR stick around and try to make the best of it. If you choose option 1, then you may have to argue with ABB and/or your ccard company about a refund and you'll certainly have some money tied up during that time and you have the annoyance of relocating. But the second option means that you don't get to decide what kind of $$ it should cost the host for you to stay. You looked at all the other options and decided that this was your best location, plumbing or not. There isnt a middle ground where you get to stay, get something fixed and not pay. Now, many hosts might refund part of the stay, maybe you would if the tables were turned, but to say that the only reasonable answer is that they fix it and give you back money isn't really true. These are houses and sometimes they have problems. You got to house 7 people in the area you wanted to be in at a price that sounds like didn't exist anywhere else, therefore there are tradeoffs.