Today I have been washing walls

Which seems odd, as I am trying to wash off water stains..... with water.
anyway, this is the view of the flat I dont show prospective visitors, water damage caused by the family above leaving the tap running, none of the baths here have overflows connected to anything, so if you are not careful, your neighbours get an unexpected shower.
I've tried water, soapy water, bleachy water and finally neat bleach, oh then I scraped the top layer off, all to no avail, the marks are though the paint work to the plaster. 
I also (on another bit of wall) tried painting over it, but the paint was too watery, so back to the shop tomorrow to ask for something with less water in it, more pigment, maybe oily, not sure.
I'm off out tonight to watch an art class, they have a live model and I might do that, probably not tonight though. I'll keep you posted.
Happy Sunday one and all.