Tankless Water Heater FAQ's
By Jackie LoBuglio - JD Supply Water Heater Outlet

1. How Do 'Instant Hot Water' Tankless Water Heaters Work?
2. How Can An 'On-Demand' Tankless Water Heater Make Hot Water Instantly?
3. How Much Energy & Money Can A Tankless Water Heater Save Me?
4. Can A Tankless Water Heater Really Provide An Endless Hot Water Supply?
5. Can A Tankless Water Heater Really Provide The Hot Shower Or Bath That My Conventional Water Heater / Storage Tank Gives Me?
6. Is One Tankless Water Heater Powerful Enough For All My Hot Water Needs?
7. Can A Tankless Water Heater Cope With Very Hard Water?
8. Do Tankless Water Heaters Have Any Limitations For Normal Use?
9. How Do I Choose The Optimum Tankless Water Heater For My Application?
10. Do I Need A 'Central' Or A 'Point Of Use' Tankless Water Heater?

Tankless water heaters only heat when water is flowing through them. When a hot water tap is opened, cold water flows into the heater unit and triggers either electrical heating elements or gas burners to turn on. As the water continues to flow through the tankless heating unit, it continues to be heated until it reaches the desired temperature (usually in the range 100°F to 140°F). When you vary the water flow rate at the faucet, a water valve or thermostat controls the amount of heat supplied so that water exiting the tankless heater unit is maintained at a constant pre-set temperature. For any particular input cold water temperature and pre-set exiting hot water temperature, the amount of energy used by the tankless heater unit is therefore proportional to the flow rate of hot water demanded. When the hot water tap is turned off, the system shuts down.

When you open a hot water tap, the tankless water heater's heating unit is activated by the cold supply water flowing into it. Whether the heater unit uses gas-combustion or electrical heating, the heat is applied rapidly to a large surface area of water which rapidly increases in temperature as it flows through the entire length of the heating unit. The water is essentially heated 'instantly', so that the time taken for hot water to reach the opened tap is essentially related to the tap's distance from the tankless water heater unit. Since heating is only applied while water flows into the unit, the amount of energy consumed is dependent only on the amount of hot water used, and any residual hot water left in the pipe between the water heater and the tap. For applications located at a significant distance from a 'central' water heater, a 'point of use' tankless heater can be used to most efficiently provide truly 'instant' hot water.

Depending on the specific model of tankless water heater that you purchase, the particular size of your existing conventional water heater / storage tank, and whether it runs on gas or electricity, you could save anywhere from about 10% to 70% off your current hot water heating bill. This energy saving is possible because most homes only use hot water for a cumulative total of about one hour per day, yet conventional water heater / storage tanks typically maintain 40 to 50 gallons (often more) of hot water at it's required use temperature for all 24 hours every day. Additionally, your old conventional water heater has most likely lost efficiency as it aged. Your new, high-efficiency, tankless water heater eliminates all the energy losses associated with hot water storage because it only produces hot water as you demand it.

Yes, a modern tankless water heater really can supply hot water continuously - unlike conventional water heater / storage tanks that can only store a finite amount of water. With a conventional water heater / tank, once you have used up your supply of stored hot water your shower goes cold, you get a cold bath, or your washing machine cannot provide a hot wash. You must then wait quite a long time (the 'recovery time') for the heater to produce more hot water at the required temperature. Because a tankless hot water heater heats the water 'instantly' as it passes through the heater unit, you will never run out of hot water - provided that the unit is correctly sized for your application (so that it's flow-rate limitations are not exceeded).

Yes, a tankless water heater really can provide hot showers and hot baths - provided you buy the optimum sized tankless heater for your specific application. Tankless water heaters are able to function at a variety of temperatures that you can choose, and can produce hot water at the same flow rate as your standard single-headed shower provides now (since 1992 all showerheads are designed to deliver a maximum of 2.5 gallons per minute, as mandated by US federal legislation). Since tankless water heaters provide an essentially endless supply of hot water, you can fill a bath tub of any size. Bear in mind that some large bath tubs draw water at unusually high flow rates, and it may be necessary to limit the hot water flow so that the tankless water heater can adequately heat the water that is being demanded to your preferred temperature. In such cases, a larger tankless water heater will obviously fill your bath tub faster than a smaller heater unit.

Yes, a single tankless heater can comfortably replace your existing conventional hot water heater / storage tank. You must simply choose the optimum sized tankless heater model to suit your home's hot water needs - which is based upon the maximum flow of hot water you need at any one time.

Since tankless water heaters do not store hot water, minerals do not have as much of a chance to settle onto the heater sidewalls. Therefore, you won't see the same scale build-up problems or corrosion issues with tankless water heaters that you may have experienced with your conventional water heater / storage tank. You can use a water softener with a tankless water heater, if you choose.

Since a tankless water heater only heats the water as you demand it, the flow rate of hot water that it can deliver is directly related to the amount of energy that the heater unit has to supply in order to heat the water to your required temperature. If the incoming cold water temperature is lower (as in winter) or you set the hot water temperature higher, the hot water flow rate may be reduced. Larger gas burners or electrical heating elements in the heater unit allow for higher hot water flow rates. Modern tankless water heaters are offered in various sizes to suit most residential or commercial needs. Even if you need to be operating multiple showers at once, a correctly sized tankless water heater can always keep up and supply essentially limitless amounts of hot water.

Volume of hot water should not be an issue in selecting your optimum tankless water heating system - all tankless hot water heaters can essentially provide unlimited volumes of hot water. The primary factor that you need to consider when selecting your tankless water heater is Your Required Hot Water Flow Rate! Always choose a tankless water heater model that can deliver the required hot water flow rate to meet your most demanding needs. The optimum tankless water heater for your specific application can often be found by understanding how many showers each model can run simultaneously. By far, the most popular sized model is usually the one that can deliver only one shower at a time (remember, that although it will only deliver one shower at a time, it can do so endlessly, shower after shower after shower). Larger tankless water heaters are available that can run two or more showers at a single time.
Bosch Tankless Water Heater Models

In most N American applications you should consider a 'Central' tankless water heater as a direct replacement for your existing (centrally deployed) storage tank water heater. A 'Point Of Use' tankless water heater may be used to efficiently provide truly 'instant' hot water in applications that would require an extended run of pipe from a distant, centrally located, water heater. In these applications, the 'point of use' tankless system can be used to either supplement, or entirely replace, your central hot water supply (storage or tankless) at that particular point of demand.