I will jump at this time and throw around my considerable weight behind Sibusiso.

Let me explain:
-> i-bathroom is obliously an English word on its way to being Zulucised (from Anglicised, see I am creative), what I did was just add i- as a prefix to the word bathroom. The next step is to make the word -bathroom sound more like IsuZulu, to do that I get rid of the "r" and substitute a better sounding Zulu letters...Lo, and behold we have Ibhavulomu.

Is this a Zulu word? No.
Is it a borrowed word? Yes.
Is it acceptable? No.
Why? Well as Mbokazi has pointed out you can either use igumbi lokugezela or other words I will show later, but Carsten said igumbi is a corner. Yes he is right, but the usage of igumbi as a room is also correct.

There are other words that I sometimes use:
-> Indlu encane = Toilet
-> Indlu yangasese = Toilet
-> Indlu yokugezela = bathroom.

The argument here is you do not necessary have to borrow words from other languages if you can easily find them in your language. This of course is not always true, some European language for example are particularly promiscuous, English is a prime example.

In closing then, I am against Ibhavulomu, as there are Zulu words to describe a bathroom. It sounds like IsiZulu, but it is a Zulucised English word.

Malandela, Wena owalandela izinkomo zamadoda, Luzumane, BazumeNdaba balibele, Lugagane olwahlaba amaTshali ezibunjini athi ayahamba agxamalaze, Mfolozi emnyama inkethabaweli........