Tankless Heaters – why use them?

I think most are familiar with tankless heaters, but just in case you’re not, I’ll touch on this topic. There are several reasons to consider using a tankless heater:

• Energy conservation – since a tankless heater heats water only when needed, they use less energy than tank heaters. Although tank heater insulation has gotten much better over the years, a heater that doesn’t have any standby heat losses will always be more efficient. Also, I would argue that since a tankless can be set at a lower temperature (since you don’t have to jack up the temp as you might with a tank in order to extend your supply), there will be slightly less heat lost through your pipes and insulation to the surrounding air due to the lower temperature differential. Our heater is set at 110° vs the 120-240° most people set for the tank heaters.
• Endless hot water – as long as your tankless is large enough to meet your needs, it can supply infinite hot water. This is great when you’ve got visitors staying at your house, and the fifth shower is the same temp as the first.
• Smaller footprint – being able to hang the heater on the wall saves a lot of floor space. Ours sits above our washing machine, so it’s not taking up any valuable space.
• Direct venting – many of the gas tankless heaters support direct venting out the side of the house. This was a big plus for us, since we were removing our old chimney to gain extra space in our kitchen. An electric tankless wouldn’t require any venting at all, but I’ve not read too many good things about them.
• Longetivity – since tankless heaters are mostly made of copper tubing, as opposed to steel tanks, they will not rust through and should outlast tank heaters by a wide margin.

Why not use a tankless?

Although opinions will differ widely on this topic, you probably already know if you are a tankless person or not. Some people, like us, get so committed to the idea that we kept at it until we had a system that worked for us. Others don’t want any hassle or to spend more money than they have to, so I wouldn’t recommend them if that describes you. I often compare them to hybrid cars.  You buy one because you want to use the least amount of energy possible, not because you think you may even out the extra cost with lower gas usage.  While the payback of a tankless really isn’t all that bad once you factor in rebates and tax credits (see below), I think the inconveniences would scare off someone who wasn’t really motivated to save energy just for the principle of doing it.  And don’t think that there weren’t many times during our troubles that I came very close to ripping ours out and plunking down a big ‘ol tank. There were moments where I didn’t care how much we had invested in it…it just wasn’t worth it. Imagine how I felt after upgrading to 1 1/4″ gas line because our gas run was a tiny bit longer than Bosch recommended for 1″ line (to which I had upgraded from 3/4″), only to find that we still had noise problems, since the unit was defective. I don’t believe that our situation was the norm, though, so please don’t take our initial bad experience as a deterrent. However, there are a few tankless traits that make them not suitable for everyone or their homes:

• Intermittent/low-flow issues – this is my least favorite trait of tankless heaters. While they excel at providing unlimited showers, they pretty much suck at the little stuff, like washing hands and doing dishes. Imagine someone washing their hands in the bathroom when the water in the pipe is totally cold. It may take 1 or 2 extra seconds for the hot water to reach the sink (compared to a tank), since the heater has to kick on once it senses the flow, but that person will not even know that you have a tankless heater. But now imagine that a second person goes in to wash their hands. At first things will be fine, because the line is already full of hot water from the previous use. But there will be some cold water introduced into the line due to the startup delay, and if they wash long enough that cold blast will make it to the sink. And that will be followed a couple of seconds later by the “new” hot water. And all tankless heaters need a minimum flow rate to even turn on, so too low of a low will always come out cold. We learned new behaviors, such as filling a sink for dishwashing or shaving, instead of using little bits at a time. But eventually we got tired of having to think so much about “gaming” the system that we eventually added a mini-tank heater under the kitchen sink. That worked out so great that we installed another one to serve the bathrooms a year later. You can read about our hybrid system below.
• Gas line size – if your gas line (from the meter to your heater) is too small, the heater will not be able to run at full output. If you don’t meet the manufacturer’s recommendations, you may have to upgrade at least part of your line. That’s not a big deal if you can do it yourself, but imagine it could get pretty spendy if you’re paying a plumber. Our unit is one of the higher capacity units, and its 160,000 BTU capacity dwarfs the 80,000 BTUs of our furnace. A tank heater doesn’t really care about the gas supply, since it’s heating a large amount of water at a slower rate. Of course, that’s also why they run low on hot water after a shower or two has depleted the tank.  They just can’t recover quickly enough to keep up with lots of showers.
• Expense – there’s no escaping the fact that tankless heaters cost 2-3x as much as tank models, but there are many federal and state tax credits and rebates available to help offset the cost. The direct vent models also usually require some fairly expensive stainless pipe, which can add $100-200.

Our funky but effective hybrid system

As mentioned above, we eventually grew dissatisfied with having to always out-think the heater when it came to lower flow or intermittent uses. Eventually, we added in two mini-tank heaters to solve this issue, as well as minimize water wastage, since we now have true “instant” hot water at most of our sinks. Although they are reducing the efficiency of our hot water system somewhat, they seem very well insulated. It does mean that some of our heating now comes from electricity, which costs more than gas, but it is definitely nice to waste less water. And if you’re curious about the energy usage, I used my Kill-a-Watt meter to average out their consumption. The 4 gallon heater uses 25 watts, and the 6 gallon uses 37. These are averaged out over several days, so they suck this energy down around the clock. Although it might be slightly more or less depending on your usage, in our case it’s like having a 60 watt bulb running 24/7. I’d rather not be doing that, but some amount of that is offset by water that does not have to be heated by the tankless anymore. And just as important, we don’t ever have to run more water through a faucet than we actually need, since we don’t have to get enough flow to force the big heater to activate.

We have a 4 gallon Ariston under the kitchen sink and a 6 gallon in the basement that feeds the basement bathroom sink, the main bathroom sink just above as well as Chloe’s sink upstairs. It will also feed our (future) bar sink in the basement.  In retrospect, we might have used a 6 gallon for the kitchen sink, because it does sometimes run out if we have to handwash a bunch of pans while running the dishwasher. But even when it does, it’s inline with the tankless heater just below, so it’s easy to “recharge” it quickly. Here are pictures of the heaters, as well as a diagram of our expensive and overcomplicated, yet effective hot water system. This is not for the faint of heart or cheap or wallet, and while we are very happy with it now, I can’t honestly say whether we would have gone this route knowing what all lay ahead.

This is our first experience with PEX (polyethlyene) water lines, and I gotta say that I am hooked. While I associate copper with “quality” plumbing, the difference in labor and effort is massive. To run copper from our basement to the new upstairs bathroom would have been a monster project. Lots of joints in tight places for both the hot and cold lines. With the PEX, I was able to run both lines as single, continuous piece. With copper I would have inevitably ended up with a leak somewhere in the middle, forcing me to drain the line and repair it while trying not to set the house on fire. With this stuff I just uncoiled it and fed it through joists and up our closet chase and up into the bathroom.

PEX lines in new 1/2 bath, along with partially completed vent:

Drain line in closet and in basement:

Maze of pipes at mini water heater. I always vow to keep it simple, but my plumbing always ends up looking like this. I’m addicted to shutoff valves, since they make it so easy to work on future projects, such as the future basement bath remodel. Now I can just work on the new pipes without having to shut off water to anything else. That’s a big deal after you’ve spent entire days without a toilet or shower because the water had to be shut off. The 2nd picture shows one of the PEX lines connected to the copper. There are 2 varieties of PEX connectors, the “official” ones that’d be used by a plumber and require a $100 crimper (or $200 if you’re working with 2 sizes) and the “Joe Homeowner” ones I used. They are pricy (about $5/connector), but they’re really cool to use. You literally just plug the pipe into it. It’s that simple. And if you have to change something later, you can pull back a spring-loaded clip and pull the pipe back out. I can’t imagine anything easier than that!

Because we don’t like the idea of wasting a ton of water just to keep a steady stream running through the heater, we put a mini-tank (Ariston GL-4) under our sink about a year ago. It is fantastic! It provides a nice buffer for the tankless, and is seriously “instant” (hot water in a couple of seconds). Although it introduced a tank to our tankless system, these heaters are very well insulated and we noticed no change in our electricity usage.

So, after a year of getting used to the luxurious hot water at the kitchen sink, we began to wonder what it’d be like to have instant, buffered hot water in the bathroom. Although I had conditioned myself to a routine of shaving only after a shower and carefully using the residual hot water in the pipe to fill the sink and rinse my face, I thought it might be nice to be able to shave any time without wasting a lot of water waiting for the hot water to get all the way across the house or to wash our hands in actual warm water. The distance problem, of course, plagues any variety of water heater, not just a tankless. Anyway, since we are also in the process of adding a half bath on the 2nd floor, we decided to add a 6 gallon Ariston (GL-6) in the basement to feed the basement bath, the main bath, the new half bath and a potential future laundry room and wet bar (once we get the rest of the house done). I started the install last weekend…

The hardest part (emotionally) was tearing out all the plumbing I had worked so hard on in the past. Since I had not foreseen the additional bathroom when I laid it all out and had since changed some ideas about the basement bathroom (future remodel), I decided to start over. This always sounds like a good idea and feels like a bad one 9 hours into the replumbing when you still can’t flush a toilet! Copper takes such a long time that I am really warming up to the idea of PEX, which I’m going to try for the first time for upstairs. Getting rid of most of the connections sounds great! Here is the first stage of the carnage…

Here’s the cleared out ceiling. You can see the before picture here.

Heater and some of the plumbing installed:

Most of the pipes redone:

My first post was a recap of all the problems that we’ve had with this heater over the last two years. Tonight’s post is a very happy one. About 10 days after I sent my long email to Bosch detailing all the steps I’ve taken to remedy the startup noise issue, I finally received a reply. I had given up hope, since they promise responses within 24 hours and an earlier one I had sent months ago went unanswered. Imagine my shock when I read these words:

Hello Julio,

I am sorry to hear that you are having so much trouble with your water heater. I would like to offer a possible solution. Since you have tried to dial in the air/gas mixture to no avail, I think that we should swap your heater for a new one. Please call our toll free tech support line at (866)330-2730 and we can set this procedure up. I have updated your record to reflect this so any tech you talk to should get it going quickly.Thanks for buying Bosch.

I called the number right away, and the tech support person took only a few minutes to get me set up with an emailed warranty return number and return instructions. I called George Morlan, the local plumbing shop where I bought the heater in December of 2004, and explained the situation to the store manager. Even though he was unable to reach Bosch due to it being after 5 on the East Coast, he said they’d go ahead and swap it if I brought in the old unit. I went home a little early, pulled the old one down, brought it in, exchanged it, installed the new one, and….

IT WORKS!!!!!!!!!!!!

Looks like all the agony and gas line upgrades may not have been necessary. My opinion has undergone a complete 180, and my new mantra is:

Bosch tankless heaters are great!

I appreciate all the suggestions that people gave to help troubleshoot the problem, but it looks like we just had the 1 in 1000 lemon. When I think back to how many times I had to fiddle with the gas/air mixture setting on the old one, it felt amazing to have this one just fire up with NO tweaking. I probably took the cover off the old one about 20x to try to adjust it. It is better than the first unit a couple ways:

1. No startup noise. None. I’ve noticed that it is even quieter than the old one was even at its best. On our ground floor directly above the heater, I can’t hear it at all. With the old one, you could always at least hear the burner fire up, or more commonly, the GRUNTING noise.
2. More stable. The old one had a really difficult time handling low-flow situations. I always thought it was typical performance for a tankless, but this one is noticeably better. While you still need the 3/4 gal/minute flow rate to get it to turn on, the burner will still stay on if you then turn it down. I’d estimate that it’ll go down to 1/3 gal/min before turning off. Big improvement!

While I wish that I had been more aggressive with pursuing this with Bosch before now, I hadn’t had any other experience with tankless heaters and therefore had no good frame of reference. If I now had to go back to our old heater, I’d know it was messed up. My gut feeling is that all of my gas line upgrades were unnecessary. While they will allow the heater to get as much gas as it can eat, I believe this one wouldn’t have made the noise even with the 3/4″ line. On the bright side, who doesn’t want enough gas line capacity in their basement to be able to run a kiln, a restaurant and a glass blowing workshop, all at the same time?

In case anyone missed the morals of this story, they are…

Tankless heaters are great, if yours doesn’t work well, it may just be a dud, and

We LOVE Bosch!!

9/7/2008 update: After living with the new heater for another year and a half, we we revise our statement to say that Bosch tankless heaters are merely OK.  Every year at the peak of summer, the heater will have a tough time maintaining its temperature, and we will get blasts of cold in a shower.  My impression is that this heater is great for “full throttle” use, but it struggles with low to moderate flows.  Again, this makes we wonder if we would have ultimately been more satisfied with a smaller unit that would regularly run closer to its maximum output.

Noise. Since day one, this heater has made one of two different noises:

• A loud, combustion-engine-sounding, house-shaking groan/grunt upon startup, and/or
• A loud whistle during operation that can be heard a block away

The noises are related to the gas valve in the unit. It is apparently very finicky and tough to get adjusted properly. If the gas delivery is too little, it’ll groan; too high, and it’ll whistle. We are often lucky enough to get both. Our next door neighbor has asked questions such as “did you know your house farts?” and “why did you have a 1kHz tone coming out of your house?” (He works for a radio station, so I guess he listens to sine waves in his spare time). While they’re laid back enough not to let it bother them too much, it bothers me that we keep projecting noise out into the neighborhood. Since we already have 2 dogs and a 4 year old, it’s best not to add to the list of noise makers! The part that drives me insane is that we paid a ton of money for this thing, so I don’t think it’s unreasonable to expect it to be quiet.

I have called Bosch tech support a couple of times, and they’ll walk me through the adjustment procedure. One time I even paid an “expert” listed on the Bosch website to make the adjustments. He turned out to be an ordinary plumber who also had to call Bosch to learn how to adjust the valve. Big waste of $$. Each time it’ll work great for as long as 24 hours, then it’ll start making one of the noises. I’ll then adjust it so it only grunts, since it only happens when firing up vs. a 10 minute whistle during a shower. I have probably tried adjusting it at least 20 times, but I can never find the sweet spot.

Earlier on, there was a possibility that the unit was not getting enough gas, since our heater is on the opposite side of the house as the gas meter. To rule out the possibility, I changed out the 3/4″ line with 1″. No change. A year later, I changed over half the 1″ line to 1 1/4″. Everywhere I tried to find it, I was asked “you want it for what??” Nobody had ever heard of someone putting 1 1/4″ in a residential application, but I pressed on until I found it at a local plumbing supply shop. There was a slight lingering doubt due to our being about 1′ over the Bosch-recommended length for 1″ line, once all the elbows were factored in. I was pretty sure it wouldn’t even make a difference, but I had to find out for sure. And besides, even though I was often mad enough to rip the heater off the wall, it was maybe $60 to change out the pipe again vs. the $1000 that the heater cost. Guess what…even the mammoth line didn’t fix the problem. Even with the furnace and gas dryer running full blast, the heater is still getting well above the minimum pressure it needs. I know, because I found a way to make a homemade manometer on the net and tested it out.

I’m not sure how we ended up 2 years down the road, not really any closer to solving our problem. The only thing that has changed is my willingness to do something drastic, if necessary. I just sent Bosch a long email today, basically as a plea to hopefully have them send someone out to replace (or somehow adjust) the gas valve. To really adjust it properly, a CO2 meter is required, but neither I nor the “expert” had one. In case worse came to worst, I found the valve online, and it’s a $350 part! For that money, we could almost buy a new (smaller) heater once the new Federal Tax credit is factored in. We’ll see if Bosch responds favorably to my email and how long my drive to replace the heater lasts. It usually dies out just as soon as I figure out how much we’d have to pay, at which point I start thinking “well, it’s just a little noise…”

Picture of the water heater right after being installed (with the original 3/4″ gas pipe) [note: the install was not quite finished, so you don't need to comment about the partially-finished temp-pressure release or the lack of pipe insulation]

Picture of the insane 1 1/4″ gas line (the black line running to the right) as it transitions to the 1″ line. It doesn’t look too big in the picture, but keep in mind that our joists are true-dimension 2×10′s!

Feb 2, 2007 update:

This story did end happily. See the new post here.

The short version of the story is that Bosch offered to replace our two year old unit with a brand new one in an effort to take care of the problem. The new one works perfectly.

Aug 19, 2008 update:

We’ve now gone through two summers since installing the new heater. Around August, we’ll find that the heater will turn off at least once during a shower. I’m assuming it has something to do with the incoming water temp being higher than the rest of the year, but it still doesn’t make sense as the flow rate for a shower is well above the heater’s minimum. Since it has happened two summers in a row, I am further convinced that there is a design flaw in this heater.