With the tankless units a minimum flow, typically 1/2 gallon per minute, is required to turn on the heater. So say goodbye to low flows of warm water, because low flows won’t keep the heater turned on.
One nice thing about the tankless heaters is that you never run out of hot water. Endless water is one of the selling points for the tankless water heater, but be careful, it could lead to an increase in water usage by the homeowner who now believes his hot water is cheaper. It can also break and you will need to call a water heater repair business to help you fix it.
Demand systems use less than $2.00 per year in electricity since they run for such brief periods of time. Don’t confuse a hot water demand system with a traditional circulating system. The demand systems only run for a few moments when hot water is demanded. Typical circulating systems run continuously for long periods and will void the warranty on the tankless units.
The tankless heaters need larger flues than tank type units if they are gas and larger gas lines, and if they are electric they need larger diameter wires to handle the high amperage currents they draw. (It takes a lot of electricity to heat water fast.) They are also quite a bit more expensive than tank type units and much more complex. If they ever need repairs they are more expensive to repair, and sometimes parts are hard to get, but then there is no tank to rust out either.
With a conventional water heater, you have a big tank full of heated water, which is slowly losing heat to its surroundings, even with lots of insulation. If it’s a gas heater it has a pilot light as well, which consumes energy 24 hours a day. Since the tankless heater does not have a pilot light and does not have a big tank full of heated water losing energy constantly, it is more energy efficient.
For our example, we will use a gas heater because it is easier to visualize than electric, but it’s pretty much the same for an electric model as a gas model.
A tankless water heater can be pictured as a coil of pipe over a campfire. As you run water through the pipe, the heat from the flames gradually heats the water in the pipe, and by the time the water has gone through the entire length of pipe it is hot. The more slowly the water travels through the pipe, the hotter it will get. If the water travels through the pipe very quickly it might not be in the flames long enough to get hot. Some heaters can modulate the heat source to even out the temperature rise for different water flow rates.
Tankless water heaters are selling like hotcakes these days. But like just about everything, they have their good points and their bad points. Before examining the pros and cons, let’s take a look at how they work.
A tankless water heater will save energy over a conventional water heater but will waste water when compared to a tank type unit. To save both energy and water install a hot water demand system pump along with the heater. That’s called being nice to mother earth.
Since the tankless water heaters need to heat the water before sending it to the fixture, it takes longer to get water than with the storage type water heaters. That leads to wasting water which no one wants to do.
There is a solution to the water wasting problem, and it’s called a demand system. It’s a small pump that installs under the sink furthest from the heater. When you want hot water you activate the pump, which pumps the water in a big loop from the water heater past the sink and on through the cold water piping back to the inlet of the water heater. When heated water reaches the pump it shuts off. Now you have instant hot water and you did not run any water down the drain.