Below is some information about the three most common types of shower in the Dublin area.

Gravity Fed Showers

Diagram-Of-A-Gravity-Fed-ShowerA gravity fed shower is the simplest type of shower as there are no electrical connections or moving parts to maintain. It needs a hot and cold water supply. However, the pressure is not great in the average house where the shower is fitted on the first floor and the tank is roughly 1-2 metres above it, this results in a just about adequate shower. Working a lot like like a tap, you open the valve and water flows by gravity, hence the name.
On the left is a diagram of a Gravity Fed shower setup.

Electric Showers

Diagram-Of-An-Electric-ShowerAn electric shower is essentially a very powerful heating element(just like in your kettle), so powerful it heats the water as it passes through it. It only needs a cold water and electrical feed and it does the rest , so no need for hot water in your hot press. They can be mains fed or tank fed .The term "Pumped Electric Shower" means a tank fed electric shower with a small built in pump so as to increase the pressure slightly,examples are the Triton t90 or Mira Elite however this is not a "Power" shower.
On the left is a diagram of an Electric shower setup.

Power Showers

Diagram-of-A-Power-ShowerA power shower is installed similarly to a gravity fed shower with one addition , a pump.It needs a hot and cold water supply aswell as an electrical supply. There are two types , one is a wall mounted unit that has the pump fitted inside, and the other is a control valve with a pump fitted in a seperate location(usually the hot press). The pump pushes water out of the shower head at a powerful rate, hence the name "Power Shower".
On the left is a diagram of a Power shower setup.