regrouting shower Advice and information on tiling and fixing tiles to a variety of surfaces

[puppy]

I am in a rented house with a very un-co-operative landlord so have resigned to repairing things myself.
The problem I have is the grouting on the shower walls is coming off. How do I go about rectifying this
without having to go without a shower as there is no bath in the house?

[welsh brickie]

scrape out and renew the grout.