This has got to be the easiest way of providing a shower.
Because it makes use of the existing water supply and drainage, very little plumbing work is involved.
One word of caution though - this is not suitable where the supply of cold water is directly from the mains and the hot supplied indirectly, or, vice versa. The difference in pressure between the hot and cold will cause all sorts of problems, not least of which is the difficulty of balancing the temperature. Before starting any work, or for that matter spending hard-earned cash, assess the supply to the bath.
Replacing the old bath taps
The basic method involves replacing the existing bath taps with a bath / shower mixer and making use of the drainage from the bath itself.
The bath / shower mixer is connected in the same fashion as an ordinary mixer tap onto the existing 22mm supply pipes.
New mixer tap shower
The new tap is fitted with a lever or similar device, which sends the water along the shower hose to the shower head. The pressure of the water supply is entirely dependent upon the water supply so, if you have relatively low pressure, consider fitting a booster pump
Changes in water pressure during operation of the shower will cause a change in the water temperature from the shower head. If for example, somebody uses a tap on the basin, this will cause a drop in the water pressure to the shower. This can give an unwelcome surprise if it turns cold but can be more serious if the temperature increases. A pressure equalising valve can help. Sometimes, mixers are fitted with a thermostatic valve to overcome this problem.
To install the new mixer, follow the procedure for changing taps.