@Nicole1378 first of all, you are the one that should offer a refund, not wait for the guests to ask, water is essential. You should have called Airbnb and canceled their reservation giving them a full refund as soon as you found out about this, you would have saved yourself from all this hassle now. I would offer something like 50% refund, they are not even able to take a shower in 5 days. But, asking for a refund in exchange for a review is extortion and it is against Airbnb policy, their review will be removed if they leave one and you have evidence for this. The fair thing to do is give them some refund, imagine you going on vacation and not being able to even shower or flush the toilet, not good.