On Demand Water Heating

Instant? Nope. There are ways to get hot water to the fixtures faster, but an on demand water heater is not one of them. Instant, and on-demand refers to something that is happening inside the water heater. That being said, your water quality plays a HUGE role in both the process of heating the water and the life of the appliance. Interested? Let's talk about it. Gas is the leading fuel source used here in the mountains. Oil is second to that believe it or not, and electric comes in third. Rinnai, Noritz, Takagi, and Navien are the leading manufacturers in gas-fired on-demand water heaters used in our area. They are excellent companies who stand behind their products. They are not the same inside though. The differences they have could be worth considering. Let's begin with water quality. The most overlooked threat to the life of this big investment. We'll talk about cost later. First, the average water temperature coming into your house is 54°F. The rating plate for gallon per minute (gpm) is for water that is 70°F. So that 12gpm water heater just went to about 9gpm at 120°F going to the house. Important to know when the difference in cost between 5gpm and 12gpm is several hundred dollars. Untreated spring water will destroy most heat exchangers no matter the fuel source. Spring water in the mountains of WNC is typically acidic in nature. Some carry a little iron in also. The heat exchanger in each of these appliances is made of copper (except one of them) and has to be very thin to transfer the heat from the fire to the water quickly and efficiently. If you notice a greenish- blue stain in your bathtub and sinks; that is the acidic nature of the water dissolving the thick brass valve inside the wall. These thin coils are very durable to pressure, but not to acid. They will begin to dissolve, and the life of that water heater is now dependent on how far acidic the water is. That being said, the one that is not made of copper... Navien has made their heat exchanger out of stainless steel. This is quite a bit more resistant to the issue at hand, but not the solution. Acid can easily be corrected, but when you do that... now you've increased the hardness by two grains. Whether the water is hard from iron, from neutralizing the water, or just hard by nature; it will create a scale inside your new investment. The water heater will be awesome at first, but ever so gradually decline. You will burn more fuel and get less hot water the longer this issue is allowed. The scale becomes a very hard blanket inside the coil that resists the heat transfer. The scale can be cleaned out of the coil, and coils should regularly be cleaned. This is not the solution for hard water though. A water softener would be necessary to protect against scale in your appliance. Just to quickly state the obvious; if the water stains the bathtub and toilets, it will build up inside the appliance too. Not to mention that $60.00+ water filter in your refrigerator trying to do all the work. The longer this goes, the worse it gets. You will likely think it's fine though because it happened so slowly that it seems normal. Now that the killer is exposed, let's move on to the investment. The average cost to operate a traditional tanked water heater is somewhere between $300 and $500 per year. That's about $25+ a month. An on-demand water heater is about half that depending on usage and water quality. Focusing on gas-fired appliances here, they will typically run $1200+ just for the appliance that will meet the demand at the temperature of water that we have here. That is just for the appliance. That's a pretty standard cost for a gas appliance if you have gas, but outrageous if you are used to the cost of electric appliances. So if we are replacing a tanked gas water heater with a tankless; wise move, but if we are replacing an electric tank with gas..... that is gonna take some careful consideration. So, just some quick math here. $1200 divided by the $150 in fuel consumption will pay for itself in eight years. Now for the fine print that gets us every time. If you do not have a gas appliance where this water heater will go, then there will be a pretty large expense in running the new gas supply to the appliance. If you do have a tanked gas water heater already and are familiar with but loads; these two appliances aren't the same. The tanked water heater operates between 30 and 80,000btu depending on size. Your on-demand of choice will be 199,000btu and may need some major changes to your existing fuel supply to provide enough fuel to make it happen. Changes in fuel source, size, and location REQUIRES A PERMIT AND A LICENCE. So we have the fuel supply aside, these things need clean air to burn that does not come from the same place we breathe. Once they have expired the oxygen from the burn, they begged to exhaust the carbon monoxide where we won't breathe it in. Good news is that most of these appliances burn so efficiently that the exhaust is not hot and can be vented with pvc pipe. It does need to come and go outside. Therefore, it takes some consideration where to place the new appliance. Rinnai, Noritz, and Takagi use three and four inch pipes for this. Navien uses a two inch pipe. Yet another expense that must be considered. The smaller things that remain are the need for a dedicated power outlet, rerouting of water lines , and getting rid of the condensation. Condensing technology is the way to go with on-demand water heating, but once the water heater is done with the condensate; it has to be gotten rid of. Some situations require a small pump. The electrical usually requires running a new circuit with a gfci receptacle. This article is simply being real from experience. I love the technology, and installing them. I do recommend them in some situations, but in others they may not be the wisest move. We will get into some of the pros once all the $$$ is addressed. Having hot water, but no macaroni to put in it isn't so great. I have seen these installations run $6000.00 and up for a brand new upfit including inspections, gas piping, venting, water piping, and condensate drains. That is getting serious. The folks that have them, love them. Now that investment is not an investment any more, but rather a preference. $6000 divided by that $150 savings now takes 40 years to pay for itself, and the warranty is well gone by then.