If your service yard adjoins to your bathroom (where the central piping inlet is located), then you can install a gas central heater in the service yard and extend the hot water pipe to bathroom. You have to drill a hole though so be careful that you do not damage any concealed piping as the cost to repair it will be astronomical. You have to also lay gas piping to the service yard. Check out City Gas for their range of gas heaters.
If your service yard is not adjoined to your bathroom, then an electric tankless heaters is your best bet. One such example is the Bennington C600. It is small and considered affordable at approximately $280.
Take note that a tankless central heater is not a perfect solution and here's why. For one, it is not absolutely instant. Depending on the location of the heater and the length of piping it has to go through before it reaches the outlet, there will be a delay. However, this applies to any centralised heaters as well. So if you have never used a centralised heater before, this is expected. You will also see a drop in the water pressure. For most cases, this should not be an issue as no one uses boiling water in huge flow unless they want to scald themselves. So most likely, after mixing with cold water, the pressure should be just right, at a temperature most people use to shower or wash up. However, if it is an issue for you, it can be easily remedied by changing the shower heads or installing water saving devices onto the tap which will increase the pressure accordingly. Though it may be an inconvenience and even additional investments, the savings (both electricity and water) later on should make up for it. Whichever type of heaters you decide on, you may want to have heated waters in the kitchen or even the service yard since you already have a centralised heater. However, as far as I know, HDB flats with concealed piping do not extend to the kitchen and service yard. In this case you have, again, three ways to go about it. 1. You can extend and lay additional piping from your central water heater to the kitchen. This option saves you the cost of another heater but make sure that
- the piping works does not cost more than the heater
- piping works are not unsightly. 2. Another way is to install another heater near the outlet to minimise any exposed piping. If you only need heated water for the kitchen sink, you can actually install it under the sink as show below
A storage heater is too big in this case therefore only tankless heater is possible. Since gas tankless heater cannot be installed in confined spaces like the cabinet under the sink, an electric tankless heater is the only option. In this case, the Bennington C600 will again be suitable. Though it will cost you another initial investment, this can be justified if: 1. Additional piping will cost just as much 2. Additional piping cannot be concealed and will look unsightly. However, do take note that you may need to lay a new wiring to support a higher ampere rating depending on the heater you choose. The Bennington C600 on a 13A socket can only run at mid power (3kW). It runs at a max of 4.5kW and requires a 20A socket. All the above options depends on the cost and aesthetic results. So below is a summary of all the available type of heaters
|Point of use (normally called 'instant heater')
|Pros: Simple to fix without the need for expensive piping
Cons: Needs one for every outlet
|Centralised Storage (normally called 'storage heaters)
|Pros: No drop in water pressure
Cons: Bulky, inefficient power usage and not on-demand.
|Centralised Tankless (or called multipoint heaters')
|Pros: Small, efficient, available on-demand
Cons: Drop in water pressure
|Centralised Tankless (normally called 'gas heaters')
|Pros: Similar to its electrical cousin.
Cons: Similar to its electrical cousin. May need to connect to an electrical point for ignition. Can only be installed in a non confined space. Additional gas piping required.