On the Level

Tankless Water Heaters

by Terry F. Meany

I have long held that some of the simpler pleasures in life are truly the most enjoyable: clean sheets, decent table wine, a sunny day in an
otherwise overcast winter, an enjoyable who-done-it detective novel and a cozy chair. High up on the list is the hot shower.

In America, we almost consider showers a constitutional right (I am surprised plumbing fixture manufacturers have not lobbied for it yet); they are a relaxing, civilizing influence on our lives that we always take for granted…until the hot water runs out. Only then do we think about the hot water tank, our own private, portable version of Old Faithful. Like so many other aspects of your building—choices in paint, flooring, roofing material—water heater selection has marketers, advocates and manufacturers lining up like so many auditioning singers hoping you will choose their tune and the back-up band that comes with them.

A water heater is simply a thermostat-controlled tank that stores and heats water. Cold water comes in through a dip tube; the thermostat switches on the heat and then shuts it off when a certain temperature is reached. This handy appliance saves us from heating up tap water on the stove and accounts for about 20 percent of an average household’s energy costs according to the U.S. Department of Energy. Heating and storing water in a tank has been the norm for years in the United States, but tankless, on-demand water heaters, long a standard in Asia and Europe, have been making inroads here. Do they work? Should you install one? If you do, will your tenants suddenly turn French on you and start pushing for the metric system?

A tankless, on-demand water heater does not store water, but heats it as it flows through the unit. Opening and closing the tap acts as an on/off switch for the heating element or burners, which adjust to maintain a constant water temperature. The more water used, the more energy required to heat it. A standard hot water tank heats a volume of cold water entering the tank based on the size of the tank and maintains that heat whether the water is being used or not. As the water cools, it incurs standby losses and must be heated again. Advocates of on-demand technology see this as a waste of energy and money. On top of that, tankless heaters take up less space than conventional water heaters and can even be installed at single fixture locations (called point-of-use heaters), although this is an expensive way to go.

Before you smack your head at the “obvious” advantages of going tankless, consider a few points.

First, an on-demand heater can only supply so much water at a time (the flow rate, measured in gallons per minute). Running a dishwasher, a couple of showers, and sink faucets all at once can be problematic, although less so in San Francisco because the temperature of the cold water entering the tank is not as cold as it would be in, say wintertime Minnesota, so the unit can heat it up faster.

Second, they are more expensive than storage tank heaters. Current list prices versus sale prices are all over the board, with some suppliers offering substantial discounts. Any cost difference over a storage tank water heater can take years to recover from energy savings.

Third, older storage tank water heaters can be made more efficient by adding an insulation blanket (5-15 percent energy savings per year), while newer insulated tanks perform far better than the old ones.

Last, the California Energy Commission states the average water heater has a life expectancy of 13 years. On-demand systems can go as long as 20.

Under equal conditions, an on-demand system would require just as much energy to heat a given amount of water as a storage tank water heater, but the heating conditions in the real world never equal those in a laboratory. The main difference between the two systems is that an on-demand system does not use any energy when not heating water (nothing is stored), therein the promoted savings. Can an on-demand system meet your tenant hot water needs? Probably, but you need some information first, based on the following questions.

How many bathrooms and fixtures need to be served?
What is the expected maximum demand for water (usually in the morning as people are getting ready for work or in the evening after work)?
If necessary, can the installation site be easily wired or gas-piped to accommodate a tankless system?
If hot water seemed endless, would your tenants just use more of it?

Water heating systems, both tanks and tankless, come with an Energy Guide label. Listed on the label, aside from the estimated cost of use, is a first-hour rating or FHR. This figure tells you how many gallons of hot water the unit can supply during peak usage. Every fixture allows a different flow of water. Low-flow showerheads, for instance, allow up to two gallons a minute while standard showerheads without flow restrictors allow three and a half gallons or more (a good reason to install restrictors if you have not already). The size of the tank or on-demand system really does not matter if its FHR is too low.

Surprisingly, tankless systems can be installed in multiple unit buildings, too. Takagi, a popular Japanese manufacturer, offers the Mobius T-M1 for apartment buildings and hotels. Up to 20 devices can be linked together under one main operating system, replacing large old boilers. Another brand, Rinnai Continuum Endless Hot Water Systems, have even been installed in Laundromats.

Energy savings (real and fantasized) aside, the other issue with hot water heating is running out of hot water. Tankless systems work as long as demand meets the system’s ability to supply sufficiently hot water. Open too many taps too far, and hot becomes lukewarm. More advanced units will regulate the flow so the water they deliver comes out at the preselected temperature, but they cannot regulate individual users. On-demand water heating is here to stay. Storage tank systems will compete with more efficient appliances. However, in the end, price, savings and reliability will prevail the same way furnaces, cars (at least until SUVs showed up) and refrigerators became more efficient. Before your heating contractor or plumber shows up with a torch and pipe wrenches to pull out your tank storage system, get the names of clients with properties similar in size, and larger, to yours and make some phone calls. You need firsthand, local experiences, not seller hype.

If you are not ready to replace or upgrade your current system, you can prolong its life and keep your energy costs down by:

checking and repairing any dripping faucets;
installing water-saving showerheads;
insulating old water heaters and hot water pipes;
making sure your tank’s thermostat is set at 120 degrees;
installing an electronic ignition device, if your tank currently has a pilot light;
keeping the burner area free of dust and dirt; and
periodically draining water from the bottom of the tank to both remove and check for sediment build-up.

Winter is Coming
There is summer rain and there is winter rain and winter is supposedly worse, although some years you cannot tell the difference. You still have time to clean out gutters, touch up flaking paint, seal up windows and replace broken glass, and test all outside drains. Does your heating system need a check-up? Has it ever had a check-up? Roofers and furnace repair guys are a lot easier to schedule now than they are in December or January. If your entry door needs refinishing or repainting, it will have to stay open for a few hours to dry (longer if it is varnished) so now is the time. This sounds like nagging, I know, but it beats working in the cold and rain.

The opinions expressed in this article are those of the author and do not necessarily reflect the viewpoint of SFAA or the San Francisco Apartment Magazine. Terry F. Meany is a former contractor and landlord. He is now a full-time writer and author of Working Windows: A Guide to the Repair and Restoration of Wood Windows, published by Lyons Press. He’s cost conscious, but not cheap, and knows deferred maintenance always costs more in the end. He can be reached at tfmeany@msn.com. Copyright © 2004 by the San Francisco Apartment Magazine. All rights reserved.