The following post is from Rob Cradock (cradock@shaw.ca)
This article talks about the personal experience of the author with a tankless water heater over the last ten years.
What is a tankless water heater?
As the name suggests, a tankless water heater provides hot water without the use of a storage tank. Also called an “inline” water heater or a “demand” water heater, these units heat the water as fast as it is used. The change in temperature from the input to the output takes only a few seconds and is constant, in my case more than 90 degrees F. The Saskatoon city water arrives at my home by underground pipe at about 40 degrees F (a little cooler in February) and, depending on how much cold water I mix in at the tap, is plenty hot enough for any use I have. The burner in the water heater has, at 120,000 BTUs, a higher rating than my furnace, at 110,000 BTUs. The water heater burner only cuts in when a hot water tap is opened somewhere in the house. The water heater senses the pressure drop when water is flowing to a hot water tap or appliance such as the dishwasher.
What is the biggest advantage?
The biggest advantage of a tankless water heater is that there is no stored water to keep hot. There is also no pilot light consuming natural gas, even when you are away. The only time natural gas is used is when someone is using hot water somewhere in the house. For the record, when only using hot water with no other natural gas appliances in use, such as the furnace, my natural gas bill is around $25 per month (in summer 2010 I had 2 months like this) and this includes all the fixed fees SaskEnergy charges that don’t depend on usage.
What is the biggest disadvantage?
The biggest disadvantage in my case is that I use a little more water, although I haven’t measured the change between before and after. As well, because the tank was a retrofit, I had to put my tankless water heater in the basement where the hot water tank was before it. There is now a lag of about 15 seconds at the tap furthest from the water heater (the kitchen) before hot water is available. If it was new construction, I would arrange all hot water appliances to be close to the water heater and this problem would go away. In all fairness, with a conventional water heater, the first several seconds are lukewarm at best but no one ever looks at that aspect on a conventional water heater.
I hear there are things you can do now that you can’t do with a conventional water heater.
There are several things you can do with a tankless water heater. One of the benefits is you don’t have to wait for the water to heat up before a second or third person can have a shower. You can even fill a 450 gallon hot tub at a temperature of 104 degrees F (the hottest that is safe for a hot tub) instead of having to wait for the water to heat up once in the hot tub (or Jacuzzi). Everyone likes the continuous hot water so much that it’s common for people to stay in the shower just a little bit longer to enjoy it.
OK, so what about maintenance?
As I said I have had my tankless water heater for 10 years. I get it serviced once every two or three years. When the technician services it, he cleans it, and replaces a seal or two. It takes less than an hour. I never have any scale build-up this way, despite the fact that the water is quite hard in my neighborhood. At the 10 year mark the technician has now put in a “service kit” which he tells me should last another 10 years. The life of the water heater should be well over 20 years at this rate.
Servicing needs to be done by an experienced technician, as the water heater is a little more complicated than a conventional water heater. It’s not that it has a lot of moving parts (it only has a few moving parts), it’s just that the technician needs to know about venturis, and so on. I have stayed with the same plumber throughout the last ten years and have had great service.
The water heater is not hooked up to the house electrical service. It uses 2 D-cell batteries, which I end up replacing about every 1.5 years.
I hesitate to mention the make of water heater I have because it has been replaced in the stores by newer versions. My water heater is in the 80% efficient range, having come out before the high efficiency versions were available. I also never had the chance to use a rebate of any kind, also before they were available.
So, how do you decide what size of tankless water heater to get?
Tankless water heaters are rated on how many appliances they can source the water for at once. Mine is a one-appliance water heater. Newer versions can be bought that are designed for two appliances or more. Keep in mind that the BTU rating goes up significantly for a larger rating as well as the cost. My family of four used this one-appliance tankless water heater all through our childrens’ teenage years. With a few adjustments, everything went just fine. No one ever had to complain about our daughter using all the hot water. It was impossible to do.
To answer the question, think about how many appliances you want to use at once that use significant amounts of hot water. Consider making minor lifestyle changes to minimize this number. In practice a family of four very rarely uses more than one appliance at once.
What about washing clothes and dishes?
Clothes washers nowadays use cold water only when most efficient so there is no need for hot water for washing clothes.
Our dishwasher has a “heat the water” setting, which we use because of the 15 second delay to the kitchen sink. It doesn’t have to do any heating after the first 15 seconds. The other setting we quite often use on the dishwasher is the 2 hr delay before starting so that any showers are done before the dishwasher asks for hot water.
So where did you learn about tankless water heaters?
I first used a tankless water heater in Brazil about 25 years ago when I was on assignment for the company I work for. I was there for 6 months. The tankless water heater was really tiny and was right beside the sink. I felt it was undersized as the water was never really hot, but realized it had to be really inexpensive to run. When it was time to replace my water heater 15 years later, I made the leap and have never regretted it. Tankless water heaters were barely available then in Saskatoon but I expect they will become more and more popular as the word spreads and as energy costs rise. They have been quite common in Europe for many years.
Have you any tips on installing one?
Put the hot water tank and the hot water appliances as close together as possible to minimize the delay for hot water.
One thing you will find is that the water pressure on the hot water tap is a little less than the water pressure on the cold water tap. This becomes important on taps that you rotate to go from cold to hot water (i.e. where the hot and cold water come out of the same tap). The effect is that you will have a smaller rotation range for hot than for cold. One way around this is to install a small pressure reducer on the cold water just after the Tee that goes to the hot water heater. This will keep the pressure the same on hot and cold. The other solution is to use separate taps for hot and cold water so the pressure difference doesn’t matter.
I don’t recommend discussing the technical details with the sales staff unless they actually have used one for themselves. Sales staff with experience in tankless water heaters are fairly rare so far, although I expect this will change.
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