On-demand water heaters are also known as tank-less or instantaneous water heaters. They only provide hot water as it is needed, eliminating the need for a storage tank. The standby losses usually associated with constantly maintaining a tank of hot water.
On-demand water heaters provide hot water that never runs out but may limit the flow rate of hot water. When you turn on the hot water tap, cold water goes into a heating unit, being heated by an electric element or a gas burner. The flow rate of hot water from a tankless water heater is typically 2-5 gallons per minute, which is less than the flow rate of the gas-fired models. On-demand water heaters may be placed directly at the source of the hot water or they may serve the whole house. Of course, those that are placed directly at the source cut back on heat losses through the piping but multiple units will be needed to serve the whole house. They are very useful for supplementing a regular water heater from a point-of-use such as a bathroom and eliminate the need of having to wait for the water to get hot. Larger on-demand water heaters that serve the whole house will have some heat losses although these are still much lower than the heat losses from a water tank.
Advantages of on-demand water heating
- On-demand water heaters take up less space than conventional tank type water heaters because they are compact in size
- They eliminate standby losses, that is the energy (heat) lost while hot water sits in a tank cooling or flows through pipes.
- Can provide unlimited hot water supply as long as the unit is working within its capacity
- They have a longer life span of 20 years while storage tank type water heaters typically have a life span of 10-15 years.
- They may be able to cut your water heating energy costs by up to 10-15%
Disadvantages of on-demand water heating
- They can’t supply enough hot water for simultaneous use such as laundry and showers
- Water may not be heated to a constant temperature unless the system is equipped with a modulating temperature control
- They require a relatively high draw of electric power because water must be quickly heated, If your current power system cannot support this, you may need an upgrade
- If the on-demand heater is gas-powered, it must be vented to the outdoors
Why regular maintenance of your on-demand water system is necessary
Like all other appliances in your home, regular maintenance of your tankless water heater system ensures that you can enjoy having hot water flowing in your house without interruption. On-demand water heaters do not need too much maintenance, and many times, the recommendation of maintaining them once a year is mostly out of good habit. However, to get the best out of your system and ensure that it is always operating at optimum capacity, maintenance is key. Over time, minerals from the water accumulate on the insides of the heating chamber thereby corroding the heating surface and reducing the efficiency of the system. Periodic purging of the system (yearly) will get rid of the accumulating minerals.
Here are some tips to help you get rid of the accumulated gunk within the heating surfaces:
There’s no use rushing to clean your on-demand water heater if you are going to burn the house in the process or even worse, electrocute yourself. Make sure you’ve turned of the main gas line or electric circuit breaker first.
You also need to turn off all the three valves.
These are the red valve carrying hot water, the blue one carrying cold water and the main line carrying the hot water into your home from the on-demand water heater.
Remove the purging valve.
This is usually a small, T-shaped handle that will ensure that you relieve any pressure that may have accumulated inside the heater. You need to open this valve slowly and carefully to ensure water does not shoot out and burn you.
Attach your hosing lines.
When you bought your water heater, three hosing lines should have come with it. Attach these to the valves that you had previously shut. If you need guidance with, simply consult the manual that was included at purchase. These hoses allow you to flush your heater system.
Open the valves of the purge port. (In most cases, turning them to the vertical position will open them).
Using white vinegar, flush out the system.
This will take about 3 gallons of white vinegar. It is not recommended to use harsh chemicals for this. Rely on the manufacturer’s instructions on how to do this. Typically, it would take about an hour.
Once you are done with the purging, the housing should be removed and the connections reattached to their respective valves.
Restart the system according to the instructions contained in the manual.
After you have cleaned your on-demand water heater, you should let the water run through the system to get rid of any air that may be trapped inside. Doing this maintenance at least once a year will ensure that you get the best service from your unit and you will have uninterrupted hot showers for years to come.
You may, however, need maintenance for your on-demand water heater more than once a year if:
- You live in an area with very hard water – some areas have water that is harder than others. If this is the case for you, your tankless water heating system will need to be descaled twice a year. This is to avoid damage to your heat exchanger.
- Your on-demand water heater is set to a temperature that is too high – If you live in an area with hard water and your temperature setting is too high, this increases your risk for scale buildup. This is because many chemicals dissolve faster when heat is applied.