Facts and Myths about Demand Water Heaters...continued
Another myth is that tankless water heaters cannot really supply all the hot water that they claim. This myth stems from the fact that tankless water heaters require a lot more thought when making a selection. With tank style heaters, you simply pick the tank size that most closely matches expected demand. In fact, they are often rated and selected based upon the number of people living in a household. Tankless water heaters require that other factors be considered, including the starting cold water temperature and the gallons per minute (GPM) of simultaneous demand. When the proper sized unit is selected and correctly installed, it can deliver all the continuous hot water you require.
Tankless water heaters are too expensive. While they are more expensive than tank style heaters, they also last 2 to 3 times longer than tank heaters. When you take their life span into consideration, they are actually competitive with tank heaters. Add to that reduced energy costs, the elimination of service expense to install 1 or 2 replacement tank heaters over 20 years and the all the perks of continuous hot water and they are definitely not more expensive over the long run.
Finally, tankless water heaters have a reputation that they can provide only lukewarm water to the tap at a sink. This reputation is not entirely accurate but it can be a weakness with tankless water heaters. First, let us consider how the unit works. As we explained earlier, they sense water flow and then fire up to heat the water. However, they require a minimum flow rate before they will begin heating. This is good because it means they don't operate when a tap is dripping or someone leaves the tap on a little bit. But if you turn on the tap for just a gentle flow, it might not be enough to initiate heating. Add to this the extra few seconds it takes for the unit to fire up and produce hot water, brief use of hot water at the sink may be result in little or no hot water. The problem can be resolved by using hot water at full flow and/or by augmenting the hot water supply with a small, local heater at the sink. Hot water circulating systems also can eliminate the problem.
Choosing the Right Tankless Water Heater
If you have decided to install tankless water heating in your home, you have some options. The best thing you can do is involve a plumber who has experience with tankless water heaters. Some manufacturers may be able to suggest authorized installers in your area. A plumber who has nothing good to say about tankless water heaters is either inexperienced with tankless water heaters or unqualified, in either case avoid such plumbers.
When determining the equipment you will use, a qualified plumber can help you decide whether to use just one water heater for your entire home, to plumb two units together in parallel, to install smaller units closer to the point-of-use or even to create a hybrid system using small tank water heaters to speed hot water delivery and tankless water heater to sustain delivery. They can also advise you on whether a hot water recirculation system would be a good solution for your home. Another consideration is whether to use natural gas or electric heaters. Solar pre-heating systems can even be integrated to further improve system efficiency.