Difference between Instant Shower Heater & Storage Water Heater 


Instant Shower Heater

Also referred to as an instantaneous shower heater, the instant shower heater heats up cold water instantly as it flows through the heating element located within the unit.


Storage Water Heater

A storage water heater is designed for multipoint use and operates with a mixer tap system. With its large volume capacity, it is able to store and supply hot water to various points throughout a home, including the shower, bathtub, wash basin, kitchen sink and washing machine.  


Tips for buying an Instant Shower Heater

1. Check for sufficient incoming water flow rate.
A required minimum water flow rate of at least 3 Litre Per Minute (3 LPM) is needed to operate the heater function.

Method to measure the water flow rate: 

  1. Using a flow rate meter: Connect the flow rate meter to the incoming water supply and check for the water flow rate. 
  2. Using a 3 litre container: Turn on the water and time how long it takes to fill the 3 litre container. If the container can be filled in 1 minute, that means you have a water flow rate of 3 LPM. Otherwise, the water flow rate will be below 3 LPM. 


2. Choose pump or non-pump.

Type of Pump

DC Pump (80W)

DC Pump (55W)

DC Pump (36W)

AC Pump (120W)

Energy Saving





Noise level





Increased water flow rate







Smart18, IM-9, AS-2, V10,CX9 RS, S8 RS, F7 RS, EVO RS, EZY RS

CX9, S8, F7, EVO, EZY

LH-5000 EP, VIZZ-98 EP


  1. All energy saving rates are compared to AC pump.
  2. The increased water flow rate is based on 2 LPM water flow rate.


  • Use a shower heater with a Built-In Pump if the water flow rate is below 3 LPM. 
  • Use a shower heater with a Pump Activator if the water flow rate is between 1 LPM to 2 LPM. The Pump Activator is specially designed for areas with low water pressures that are too weak to activate the Built-In Pump the unit. 
  • You may choose a shower heater without a Built-In Pump if there is a consistent water flow rate of at least 5 LPM to operate at optimum performance. 

3. Choose rainshower or standard shower.

Rainshower Set

Rainshower Set

Standard Shower Set

Standard Shower Set

9” extra large rainshower head + 4.3” standard shower head 4.3” standard shower head
3 or 5 spray setting 3 or 5 spray setting
With 3 way diverter Without diverter
With Gen C stop valve With Gen C or T-type stop valve


4. Choose a design to embellish your bathroom.
When choosing a shower heater, you may draw inspiration from your existing finishes. Alpha offers shower heaters in different styles and a wide range of colour options to cater to various bathroom design styles.



How to install the Shower Heater

1. Check the installation point.

Alpha Instant Shower Heater heating elements are available in 4.2kW and 3.8kW.

  • The cable size should not be less than 4mm2. Usage of a cable with a size less than 4mm2 might cause the cable to overheat or burn after long use. 
  • The shower heater must be permanently connected to an electricity supply through a 20A double pole linked switch. 
  • Do not use a 13A/15A plug and socket. Wiring behind the shower heater outlet is recommended. If wiring behind the unit is not achievable, use the SIRIM-tested & ST-approved Splash-Proof Water Heater Connector from Alpha. The Splash-Proof Water Heater Connector is a special plug and socket that is rubber sealed to prevent water seeps, anti-fire and strong in anchorage to ensure utmost safety in the bathroom. 


2. Make sure the water connection piping is installed correctly.
The Alpha Shower Heater inlet is on the left and outlet is on the right.

  • The water connection should use ½” BSP standard piping.

3. Install the shower heater according to the recommend mounting arrangement.

  • The bottom of the heater is 1.5 metres (5 feet) above the floor of the bathroom. 
  • The distance between the incoming water supply and the stop valve is 10 cm (4 inches). 
  • The distance between the shower heater outlet and the sliding rail is 15 cm (6 inches).