How do I hold someone accountable?

My roommate and I bought a washing machine on kjiji a couple of weeks ago and there were no red flags at all from the seller but, when we turned it on to test it, it started leaking, which is a big problem in my house because I live in a third floor flat in an old building. This caused water damage, even though we turned it off as soon as we saw water. I contacted the seller about this and she said there we no issues with it. Today, we took the time to see why it was leaking, we noticed the pump wasn’t working properly. Is it reasonable for me to ask that the seller pays for the water damage, as this was something which she did not tell us? If so, how do I do that? Also, how do you install a bloody washer pump? All I wanted was to be able to wash my clothes without walking to the laundromat especially in winter, when it can be below -20 degrees Celsius, I feel cheated and kinda angry.