Tankless water heaters

[jraabe]

Here is a size comparison between a tank and tankless water heater.



The link below is to one brand of gas fired tankless (instant) water heater. Look at the flow rate chart at the bottom of the page. If you have water coming in at 40º and you want 120º hot water coming out, then you have an 80º temperature rise. This particular heater will give you a flow of 3.3 gal/min at that rise. Others will vary and most electric units will be considerably lower. A modern shower uses about 3 gal/min or less (You can test yours with a 5 gal bucket and a watch that can time an accurate minute).

The main problem with tankless heaters is when multiple fixtures want hot water at the same time. Then the flow rate can exceed the unit's capacity and everyone will get warm or lukewarm water rather than hot. While the installed cost is higher than a tank heater, the running costs are much lower and there is usually less to wear out over time. They are also space efficient and can hang on a wall.

http://www.plumbingsupply.com/takagi.html

Here is another supplier: http://www.tanklesswaterheaters.com/

2 — Additional notes from Tom:

Bosch has great tankless heaters under the "Aquastar" brand name. I will be buying this one when I setup the new place:

http://www.controlledenergy.com/html/aquastar/125hx.html

The 125HX model powers itself. You dont have to worry about pilot lights or power outages and all that stuff.

3 — From Damian:

There are now models that will supply hot water to 2 or more outlets. "This old house" had a multiple outlet featured in a recent show. It would supply hot water to the shower and w/machine. This unit also used an electric spark to light gas instead of a pilot light. The big advantage is having hot water continuously 24/7— great for a large tub. My mother is getting one in her new place — people use them in Japan and Europe quite a bit.

4 — Here is a more detailed report from an engineer I trust (he produces inexpensive detailed reports on house issues). http://www.dulley.com/docs/f678.htm