rent abatement for unusable bathroom?

[baddison]

My roommate and I I live in a 3 story, 2 apt building. We have a lease.
A plumbing problem in our bathroom rendered it unusable before and while repairs were being done. The landlord told us to use the bathroom in the empty apartment downstairs, which was under construction, until it was fixed. This took over a week. Considering this was an inconvenience we brought up a rent reduction to reflect the week we did not have a bathroom in OUR apartment. He said, "No Way, I provided you with a bathroom". Now two weeks later, the pipes are again leeking through the wall. It turns out all the repairs will have to be done AGAIN. This will mean tearing the walls apart again and so of course the landlord has told us to use the downstairs apartment's bathroom until the job is finished. I would not necessarily push this issue, except that we have been dealing with similar issues since we moved in two years ago (carpet falling apart, ceiling collapsing, etc) and the landlord is not very accomodating.
My question is, do we have the right in this situation to reduce our rent. And if so by how much and how should we go about it.

I really appreciate anyone's help in this matter.