Water stains surrounded by plaster on wall? OK my neighbor's bathroom is behind a wall contained by the entrance...

OK my neighbor's bathroom is behind a wall contained by the entrance hall contained by my apartment. There was river leaking into my wall when my neighbors took a shower. The apartment owner get a plumber in and he come and looked at my wall and apparently fixed the problem on my neighbor's side, sealed up the shower/bath etc. However, within are still some water stains on the plaster of my wall, though I'm rather sure there is no more river coming in. (They seem to be to be old results not new ones.) I hold tried everything to dry them out, from turning up the heating to using a dehumidifier. I don't want to paint the wall beforehand it dries out properly. What could be the problem, and how can I fix it? Thanks!
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Answers:    Depending on the location of this wall - whether it is in a reheat place or a cold place - and depending on the humidity in your nouns, a plaster wall can take weeks to dry out. Using a humidifier is not as influential as a heat source,. Even a spotlight would lend a hand. If this is a 'real' plastered wall, and not plasterboard, it can take even longer, as the entire nouns between your wall and the bathroom wall would be damp.

You can use a special purpose sealer, or a coat of grease base primer, or even shellac to stop the stain from coming through when you finally do paint, but you do obligation to use something. And make sure you cover an nouns rather larger than the nouns you can now see - influence by 50% - as these stains tend to leach in adjectives directions
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You got the right concept, do not paint until the wall is very dry. When you do paint, use a stain blocker such as KILZ first. That will block the stain that WILL otherwise bleed through several coats of paint. The dehumidifier will help out, but it is still going to take awhile.