Tankless water heaters. Any opinion?

[elfreth]

Have you looked into electric tankless, rather than gas? That might be better for you.

Gas is better because gas will heat faster than electric and thus you have a higher flow rate. That means you can get a single gas tankless that will service two showers or more at once; you can't get an electric one for that.

As hig stated, you do have to wait for the water to warm and then wait for it to get to your shower/sink. Thus, having it close to the point of use is a facter.

They make point of use water heaters too - small ones for your sink/dishwasher etc that runs until the main one (tankless or tank) starts sending the water hot.

In addition to not rotting out like a tank heater; the tankless is way smaller. I have a NEW electric tank in my new place; I love this thread since I really wanted to replace it in order to get the space savings.

Based on what HIG says, maybe I will see if I can get a full size one in the master bath and then a regular one for the rest of the place. Our problem is that we ONLY have electric service, so gas is out.

As HIG points about having to wait for the tankless hot water; well I have to wait for my tank hot water too, and for the sink it isnt usually something I wait for. So, I might get a point of use one to try out for the bathroom sinks:

Electric Point-of-Use Products by Ariston and PowerStar

Also, the tankless won't run out of hot water...... That might be a reason why some people don't see a cost savings - they are taking longer showers

[elfreth]

.... I wouldn't waste extra money on super efficient. You'll never make up the difference in investment.

From what i saw on the bosche website in terms of savings (tankless vs tank) you don't save all that much in any case (electric comparison). But, that comparison assumes that you are flushing the hot water tank when you are supposed to, and it hasn't got any sediment. Yeah, right. I NEVER once flushed out a hot water tank; actually maybe my dad made me drain a hot water heater once when I was 14...

If it is a summer house/rental then I bet you could; otherwise the reason to get one is probably space savings, limitless hot water, life of the unit.

[HogIslandGrip]

Also, don't take the advice of the amateurs at your local home centers, or Plumbers looking for a quick buck. I was looking at the Paloma at HD and the "expert" there said that there was no difference in venting. I called Paloma's customer service hotline and was told the truth about the venting.

Totally true, and the venting requirements don't just differ between brands, but also between models of the same brand. Paloma also offers online installation certification.

Based on what HIG says, maybe I will see if I can get a full size one in the master bath and then a regular one for the rest of the place. Our problem is that we ONLY have electric service, so gas is out.

As HIG points about having to wait for the tankless hot water; well I have to wait for my tank hot water too, and for the sink it isnt usually something I wait for. So, I might get a point of use one to try out for the bathroom sinks:

Electric Point-of-Use Products by Ariston and PowerStar

Also, the tankless won't run out of hot water...... That might be a reason why some people don't see a cost savings - they are taking longer showers

I would get a mid-sized unit and install it right next to the bathroom, if possible. Look closely at that minimum flow rate. Look for something between .4 and .65 gal. per minute. I don't think you'll see any models that go below that, but they are always improving.

One of my other problems with it is that if I go to rinse out a pot or pan, for instance, I'll turn the water on, thus activating the heater, use a little water to rinse, turn it off, and never get any hot water. However, having activated the heater, I have now heated water that I didn't use. So now I have to make sure that the faucet lever is over to the cold side whenever I just need to quickly rinse something.

Alot of people take advantage of the "endless" factor, but for me. it's been nothing but drop-outs. I call it the freeze-or-fry effect.

[HogIslandGrip]

I may also one day have a change of heart and switch mine out for a Bosch Aquastar 1600H, if I can move it closer to everything, witch will require rethinking the venting. We shall see, but now is not the time for me.

[CapnMarko]

Alot of people take advantage of the "endless" factor, but for me. it's been nothing but drop-outs. I call it the freeze-or-fry effect.

Our neighbor Patrick was having an issue with the temp go up and down or out on his Bosch. It wasn't a flow issue as it happened when he had the shower cranked on. Bosch had someone replace the 'sensor' or 'chip' or some such advanced thing. I think it took two tries but it now works with out any problems.

You might want to jaw at him some first to see if it's an issue you can get resolved before ripping the thing out (unless you already ripped it out.)

[rumdrinx]

I am having many feelings of inadequacy with respect to my homework. I have owned two houses, never gave the water heater any second guessing (only its age and the big yellow EFFICIENCY sticker).

so I have a lot to read and will come back at you soon with questions!

[elfreth]

I am having many feelings of inadequacy with respect to my homework. I have owned two houses, never gave the water heater any second guessing (only its age and the big yellow EFFICIENCY sticker).

so I have a lot to read and will come back at you soon with questions!

next you will be saying you never thought about metal roofing



I just never got around to it. Actually the tank hot water heater in my old house got replaced with another tank because it was just before I moved.

[elfreth]

I would get a mid-sized unit and install it right next to the bathroom, if possible. Look closely at that minimum flow rate. Look for something between .4 and .65 gal. per minute. I don't think you'll see any models that go below that, but they are always improving.

that min flow rate is definately something I'll keep in mind. Of course those numbers mean NOTHING to me. 1/2 gal per minute seems like a lot of water for a sink. The other thing is the electrical requirements; I have a new place but I don't know what the electric really is in there. 200 volt rather than the 120?

Either way I think we will be waiting awhile before doing anything. But I sure would love to get the space back from the tank water heater. Plus I am very worried about leaking (I'm on the 4th floor of a condo) of anything; tanks will leak eventually.

[HogIslandGrip]

Our neighbor Patrick was having an issue with the temp go up and down or out on his Bosch. It wasn't a flow issue as it happened when he had the shower cranked on. Bosch had someone replace the 'sensor' or 'chip' or some such advanced thing. I think it took two tries but it now works with out any problems.

I remember discussing this one with you. After many different tests I am 100% sure that it is the flow rate (I can indeed get endless scalding hot water when I run it at full blast. Most shower heads have restrictors as it is, and when you mix in cold water to temper it so as to not get severely scalded, you are reducing the flow of the hot water, cutting the machine off. I've had people give me all sorts of suggestions, but everyone of my tests points to minimum flow rate. I may have better luck with a mid-sized whole-house model where the min. flow rate is .6 or less. From the product specs of your heater, it looks like your minimum is somewhere around .5-.6.

that min flow rate is definately something I'll keep in mind. Of course those numbers mean NOTHING to me. 1/2 gal per minute seems like a lot of water for a sink. The other thing is the electrical requirements; I have a new place but I don't know what the electric really is in there. 200 volt rather than the 120?

Either way I think we will be waiting awhile before doing anything. But I sure would love to get the space back from the tank water heater. Plus I am very worried about leaking (I'm on the 4th floor of a condo) of anything; tanks will leak eventually.

It should also be noted that a tankless model still has a minimum amount of water in it at all times, and that they are not immune to corrosion. If they fail, you will still get a steady stream of water flowing out of it, and you could very likely wake up to a flooded basement. The likelihood of this is probably less than a tank heater, though. You could probably catch that spray of water and shut it off more quickly than say when your tank goes and dumps 40 gallons and then continues to flow.

[MayfairMeat]

I'm installing my new 50 gallon tank this weekend. I will be installing Solar PV and water heating this spring, so the gas usage isn't an issue.

Also, don't take the advice of the amateurs at your local home centers, or Plumbers looking for a quick buck. I was looking at the Paloma at HD and the "expert" there said that there was no difference in venting. I called Paloma's customer service hotline and was told the truth about the venting.

What kind of roof size do you have? Straight-through? Standard Airlite?

I was wondering if I buy a larger corner straight-through or a porchfront... how much energy I could generate by covering the entire roof (save for the gas flu chimney and the bathroom skylight)... with PV.

Would it be enough to run my fridge and the lights off of it?


How big of a battery would I need to install in the basement and how long could I stay off the mains and stay on solar?



Or will I save money by partitioning circuits in the house to Solar PV and keeping the hgih-load stuff (fridge, dryer) on the mains while ceiling fans, lights and computer equipment run off solar?

[NE19149]

Regarding people that are PARANOID about water heaters LEAKING:

You know, there ARE devices to prevent major flooding...
There's a solonoid-operated shutoff valve that detects even a tiny layer of water on the basement floor, and shuts off the flow to the heater, as well as setting off an audible alarm.

[billy ross]

High efficiency gas heaters can't vent via a regular (brick) chimney since the exhust is so cool it will condensate on the brick inside the chimney. You vent with PVC pipe usually.

I would ask a manufacturer regarding the 'salt air' factor.

Almost correct. It doesn't matter whether the chimney is brick, terra cotta, or even stainless steel. The condensate would be very bad for the chimney. I think it has something to do with acid forming from the products of combustion.

[billy ross]

We just installed a gas tankless water heater in my house. Luckily we were able to vent it outside. I have mine set hotter than my old tank heater since there's no waste in heating and reheating water that's not being used. I'm enjoying the hotter showers.

The biggest surprise for me is the wait factor. You have to run the water for a good 60 to 90 seconds to get hot water. I have yet to figure how what the minimum flow of water to get the heater started up is. Also, I could be wrong, I think the water pressure in my shower has lessened with the installation of the tankless heater.

You may have debris from the changeover blocking your showerhead or your shower valve.

Tankless heaters are also designed to lessen the flow when they can't keep up with the demand, so the temperature is constant. If you run water elsewhere when you think that the shower is weak and the shower drops off considerably, you've found your culprit. Setting the temperature unreasonably high exacerbates this.

[billy ross]

Hate mine! Hate mine! Hate mine! Hate mine! Hate mine! Hate mine! Hate mine!

Where to begin.

I think placement is everything. The farther away from your points of use, the worse the performance. Mine is about 40' away from the shower head, thanks to the stringent venting requirements.

Electric whole-house models require at least three breaker spaces, usually 60 amps each, and heavy gauge cable as well. It's possible I may switch to one of these, as I have the breaker space for it, but...

Another consideration is flow rate. Most articles I've read talk about the maximum flow rate. None of them discuss the MINIMUM flow rate required to activate the heater. Mine is a Bosch Aquastar 2400, and it's minimum flow rate is .8 gal per minute. That's kind of high. When I get the temperature of the shower comfortably adjusted, the hot water flow goes below the minimum and the tankless unit shuts off. About a minute later there is nothing but icy water, so I'll readjust the valve, wait another minute, and now the water is scalding, so I adjust it again, and the whole cycle repeats. I've started taking showers with the bathroom faucet running in order to keep the hot water flow rate up. And wasting water.

With simple hand washing, I turn the water on, wait then get impatient. I finally wash my hands, and just after my final rinse, I might get some hot water out of it. I've just paid to heat water I didn't use. Kind of like a tank.

And forget about a nice trickle of warm water. It's not happening, thanks to a high minimum flow rate.

I also haven't noticed a significant change in my gas usage from before the installation of the tankless. So much for savings there.

Now, I still think it's a neat concept. I will probably install a small point-of-use unit in my shop bathroom, right next to the sink. If I were to do the house all over, I would probably go with two or three smaller tankless heaters placed as closely as possible to each point-of-use.

I do know other folks with tankless heaters, and they are having varying experiences. Cpnmarko, for instance, has a Paloma Legacy series, which has a lower minimum flow rate, but also requires a pilot light. He has not had the same issues that I have had. Another friend has the Aquastar 1500, which also has a lower minimum flow rate, but their shower is also equipped with multiple wall jets, thus increasing flow rate.

As it stands now, I'm probably going to sell the unit on craigslist to someone who has more appropriate conditions for it, and I'll get a high-efficiency tank model to replace it.

Like everything else, these things are made by the Japanese, the Germans, and the Americans. Just as typically, the German and Japanese models trip over themselves. Bradford (the main American company), makes a pretty clever unit, a low-storage, extremely high recovery model, which seems to be the best of both worlds, and I will install one as soon as it makes sense to do so. I admit to only having spoken with the rep about it and researched all of the models, and this in one of the reasons I am excited to try one.

[billy ross]

Electric costs about 30% more to operate. I would stick with Gas. I think they all have a Vacation mode, which keeps it at a VERY low temperature while you are not at the house. Since it is probably a seasonal property, I wouldn't waste extra money on super efficient. You'll never make up the difference in investment.

The tankless models don't make hot water until the faucet is turned on. This explains the delay. In other words, if the water isn't running they are always on vacation mode.

[billy ross]

Gas is better because gas will heat faster than electric and thus you have a higher flow rate. That means you can get a single gas tankless that will service two showers or more at once; you can't get an electric one for that.

As hig stated, you do have to wait for the water to warm and then wait for it to get to your shower/sink. Thus, having it close to the point of use is a facter.

They make point of use water heaters too - small ones for your sink/dishwasher etc that runs until the main one (tankless or tank) starts sending the water hot.

In addition to not rotting out like a tank heater; the tankless is way smaller. I have a NEW electric tank in my new place; I love this thread since I really wanted to replace it in order to get the space savings.

Based on what HIG says, maybe I will see if I can get a full size one in the master bath and then a regular one for the rest of the place. Our problem is that we ONLY have electric service, so gas is out.

As HIG points about having to wait for the tankless hot water; well I have to wait for my tank hot water too, and for the sink it isnt usually something I wait for. So, I might get a point of use one to try out for the bathroom sinks:

Electric Point-of-Use Products by Ariston and PowerStar

Also, the tankless won't run out of hot water...... That might be a reason why some people don't see a cost savings - they are taking longer showers

If the new tank is in the same location as the old tank, you still need to wait until the lines are full of water from the tank, and then you need to wait until the water in the tank is hot. Thus your present lag will still be extended by 60-90 seconds. If you relocate the new awh closer to the point of use, it could in theory be a wash, but that is doubtful.

[billy ross]

Totally true, and the venting requirements don't just differ between brands, but also between models of the same brand. Paloma also offers online installation certification.


I would get a mid-sized unit and install it right next to the bathroom, if possible. Look closely at that minimum flow rate. Look for something between .4 and .65 gal. per minute. I don't think you'll see any models that go below that, but they are always improving.

One of my other problems with it is that if I go to rinse out a pot or pan, for instance, I'll turn the water on, thus activating the heater, use a little water to rinse, turn it off, and never get any hot water. However, having activated the heater, I have now heated water that I didn't use. So now I have to make sure that the faucet lever is over to the cold side whenever I just need to quickly rinse something.

Alot of people take advantage of the "endless" factor, but for me. it's been nothing but drop-outs. I call it the freeze-or-fry effect.

Your temperature is set too high. Lower the temperature and your shower will have less cold, more hot water, and you will be less likely to fall below the minimum threshold. Alternatively, remove the flow restricter from your showerhead and take a real shower - that will increase the gpm through the infernal machine.

[billy ross]

that min flow rate is definately something I'll keep in mind. Of course those numbers mean NOTHING to me. 1/2 gal per minute seems like a lot of water for a sink. The other thing is the electrical requirements; I have a new place but I don't know what the electric really is in there. 200 volt rather than the 120?

Either way I think we will be waiting awhile before doing anything. But I sure would love to get the space back from the tank water heater. Plus I am very worried about leaking (I'm on the 4th floor of a condo) of anything; tanks will leak eventually.

A new lavatory (bathroom sink) faucet delivers 2.0 gallons per minute, and I feel that that is weak. So do most showers. That is total, mixed hot and cold.

In the USA, residential electric services are 220 volt, but what varies is amperage. Years ago, you would see 15 and 30 amps feeding a whole house. Nowadays people get stuck on 200 amp, but I feel that 100 amp is usually adequate for a house in Philly with gas appliances. Keep in mind that all new electric appliances like fridges and a/c's which used to be energy hogs are now very stingy in their use of power due to Kyoto. However, electric heat and automatic water heaters and the like will tax an electrical system, and you need to figure out what kind of electric service they call for.

[billy ross]

I remember discussing this one with you. After many different tests I am 100% sure that it is the flow rate (I can indeed get endless scalding hot water when I run it at full blast. Most shower heads have restrictors as it is, and when you mix in cold water to temper it so as to not get severely scalded, you are reducing the flow of the hot water, cutting the machine off. I've had people give me all sorts of suggestions, but everyone of my tests points to minimum flow rate. I may have better luck with a mid-sized whole-house model where the min. flow rate is .6 or less. From the product specs of your heater, it looks like your minimum is somewhere around .5-.6.



It should also be noted that a tankless model still has a minimum amount of water in it at all times, and that they are not immune to corrosion. If they fail, you will still get a steady stream of water flowing out of it, and you could very likely wake up to a flooded basement. The likelihood of this is probably less than a tank heater, though. You could probably catch that spray of water and shut it off more quickly than say when your tank goes and dumps 40 gallons and then continues to flow.

Tankless heaters have non-ferrous heat exchangers. These are much less prone to rot out and fail. On both tank-type and instantaneous heaters one can buy valves to install on the feeds which measure the flow rate and shut down if an equal amount does not run both into and out of the unit (like a lifted relief valve or a failed tank). These are great when there are living spaces immediately below the awh. In addition, when a 40 gallon heater fails, it doesn't spew out any more water than an instantaneous tank would. The tank never actually drains; the water which leaks out is replaced with new water coming in from the street. Even when you secure the incoming water, the tanks don't really drain, as the water is locked in until the vacuum is broken.

[The Philly Boy]

I jsut bought a new 50 gallon tank. I was looking at tankless, but the venting would not work for my home. You can't vent it through the existing chimney like my current HWH. It needs to be vented Horizontally through a wall or Vertically through the roof.

I'm not sure about the salt air factor. I hope this helps.

No such thing as a HWH.