And shower water is “grey water” ie unsanitary. There are so many issues with this it doesn’t bear thinking about. It’s not a matter of owners voting whether to fix it or not – it’s a health, health and safety, and liability issue. Call your strata manager and get them to arrange to fix it. The Sinking Fund will cover it (if you have a sinking fund…..).
As for the first poster, agree, no “cut off” time for showers, but this falls into the realm of ensuring not interfering with the comfort etc of others in the block. If they are disturbed by the noise it’s no different to someone playing music loudly etc. But as previous posters have suggested, plumbing is usually installed to create as little noise, interference as possible. Clearly something has gone wrong here.
Plumbing is a Body Corporate / Owners’ Corporation issue. Your neighbour with the problem should report it to the Executive Committee or Strata Manager and get it investigated.
You should definitely NOT be subjected to other’s plumbing in a unit development. If you are, it suggests there’s a problem with the building or the plumbing.