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rayyy
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# Posted: 26 Dec 2012 15:07
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To me,keeping 20 or 30 or even 40 gallons of water hot 24 hours a day,7 day's a week is crazy.That's like having 40 to 80-1/2 gallon tea kettles going on low flame at all times on the stove for you possibly usage of 2 or 3 or even 5 gallons of hot water.These little on demand water heaters give you all the hot water you need when you need it.No wasting gas and energy for any other time you need hot water.And their reasonible priced.I highly encourage you to concider on demand if you are thinking about installing a new hot water tank.
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MtnDon
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# Posted: 26 Dec 2012 18:32 - Edited by: MtnDon
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I think it depends on a number of factors; more than simply the theory that not holding hot water in a storage tank makes more sense. There are places and situations where a tankless may be better suited, but I believe a blanket statement that one type is best for everybody and everywhere is wrong.
A small cabin with all plumbing fixtures within a small radius of the heater may be better served by a tankless heater. Remember to match the degrees of temperature rise required along with the flow required. Some cheap tankless heaters can not handle 50 degree F incoming water at a high enough delivery rate.
A situation with a larger cabin or house, with longer runs to a bathroom or a laundry brings up the issue of waiting for the hot to arrive and wasting the cold water until it does arrive. This is one thing we have in our home, built 1985. Yes it would have been nice if the plumbing could all be closer to the water heater. But it is not and there are thousands of homes with the same fault. Living in a desert and being hooked to a municipal water system does make one not want to waste water down the drain while waiting for hot water. The solution we chose for that has a few parts, the first being a recirculation pump. In short, a small low powered pump circulates hot water from tank to the furthest fixtures. Pipes are all insulated. A timer is set to run at our usual use periods. There is also a push button at the sinks and shower that activates the pump on demand at other times. Press the button a minute before the shower and the water is warm as soon as the shower control is opened.
Of course we could also have installed a second tankless heater closer to the far end of the house. I've seen that done, but that boosts the investment in hardware, which is already high for most tankless heaters. I do not include the cheap Ecotemp units in a general discussion as they have too many limitations for everyday use in the average normal home.
We have a tank type, natural gas fueled, heater in our main home. It is a condensing type; 92% efficient. The vent was redone with PVC pipe. The exhaust is that cool. It did not cost as much as a tankless with the reuired capacity would have cost. And, in our case at least, the gags pipe was sufficient for the condensing heater but was not large enough for the tankless.
We also have a solar heater mounted on the roof. Water is heated in a closed loop system and transfers heat to the tank water. The gas is almost never used in summer. You can't do that with tankless.
A tankless is not always actually better than even a more normal or standard tank type water heater. Links below to a couple of articles that should be read by anyone building new or thinking of replacing a heater. (replacing a tank type with a tankless nearly always requires a larger gas pipe size, btw)
Chicago Tribune article
Green Building Adviser article
Article on water heater choices
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Borrego
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# Posted: 26 Dec 2012 21:14
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Once again Don is right......doesn't it get old, Don?  I just remodeled a house and decided, after consulting with plumber and owner, to put in a tanked heater instead of a tankless, even though we already had the tankless on site. It was determined that due to number of bedrooms, users, size, layout etc, that it would take more than 1 tankless to supply this home, and the overall initial cost and longterm costs would render the tankless the less 'green' option. It just varies from situation to situation...
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MtnDon
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# Posted: 26 Dec 2012 21:27 - Edited by: MtnDon
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Add to the above; I forget the mfg, but I have seen warranties that exclude heaters installed in areas where the water is at or above a certain hardness. They build up scale. Scale can be cleaned annually but that is a bother and maybe an expense if you can not do it yourself. There's just a lot of things to be considered before making a selection for the best water heater.
6 - 7 years ago I was a big fan of the tankless heater. That was before I started researching new heaters in anticipation of needing to replace one at some point. For our situation it became obvious a tank was better. The instant hot water with the recirc pump is very nice. Tanks heaters are not bothered by a fluctuating temperature, or worse cold water, when very low flows are being used.
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TomChum
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# Posted: 26 Dec 2012 23:05
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My dad has an on-demand heater, and it sounds like a jet engine whenever it goes off. Pretty darn loud. Something to think about. And it has to go off, full blast, EVERY time someone turns on any hot water faucet.
For a small recreational cabin (not living in full-time) of course on-demand is better, there's no sense keeping it hot in a cold cabin, and who wants to wait for it to warm 50 gallons? Or drain 50 gallons when you leave?
If a house is heated full-time with gas heat, and a tank-type waterheater is inside the house there is no net loss because the heat leaking out of the heater remains within the house, and the gas furnace runs less often. No change in your gas bill during a season while the heat's being used.
If the tank is in an unheated part of the house, then that heat that leaks out of the tank is LOST.
If you use air conditioning in the house, and your airconditioner has to eject the heat that leaks out of your tank-waterheater, then you are wasting money during the warm seasons.
At higher latitudes where houses have no airconditioning, the convenience is a reasonable attribute to have a tank-type heater inside the insulated envelope.
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silverwaterlady
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# Posted: 26 Dec 2012 23:22
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Thoughts on using pex plumbing and on demand? Our city house was built in the early 1950's. Plumbing is the original lead pipe. Hot water tank was last replaced about 20 years ago.
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Storogoth
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# Posted: 27 Dec 2012 01:21 - Edited by: Storogoth
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I replumbed our 100 year old Denver square a few years ago and replaced all of the galvanized pipe (you probably have galvi, not lead pipe Ms. SWL) with copper and intended putting in a circulating pump so ran a 1/2" copper line from the upstairs bathroom back to the tank heater. I heard about the possibility of natural convection of the hot water and figured that even if it did not work I could always just install the pump at the heater. I found out that for my application, the elevation gain in the house, and the length of the run, it worked perfect.
From the upstairs bathroom split (sink & shower) I insulated the return pipe the entire 9' vertical & then about another 10' of the horizontal run so I was maybe 6' from the ball valve at the heater and then a T to the 3/4' hot main at the hot water heater. I run the sink upstairs to get the water in the hot line up to temp upstairs and then close the ball valve down to about half closed to regulate the flow of return water. It keeps flowing and the circulation to the bathroom keeps the water very warm at all times. It does take a second and a half a glass to bring the warm to the tap but saves me quite a bit of water not to have to pull the hot water all the way upstairs every time I wash my hands. Granted it is not the 130 degrees that is coming out of the tank but it's maybe 120 or so.
I'm sure that it does cause the temp of the water in the tank to drop a couple of degrees because it is constantly cooling as it circulates. Probably a few cents of gas a month to keep it up to temp. Maybe even more on a night like tonight when it might hit 5 degrees here in Denver. I figure that I do save a bunch on my water bill and do not pay for the electricity that the pump would use.
Granted it does take a few parts of the install to have to work right. Length of the run, access to get the circulation line from the far end of the house (very hard to do in some newer construction) and probably my climate too.
I will certainly use a small on demand tankless system in the cabin when it comes time next year. After hearing some of the issues they present, I will install it with unions so that I can remove it every fall and haul it home so that i will not freeze on me.
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Martian
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# Posted: 27 Dec 2012 07:00
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I have a 10 gal, 120vac water heater. Its 10' to the furthest fixture. I get all the hot water I need for my uses 24/7, and it cost less than $10/mo for the electricity.
There are two reasons I went this way. Mainly, its because, to conserve water, I generally use a very low flow rate that wouldn't activate the on-demand heater. The second is because we use untreated well water that is pretty hard; on demand heaters are not recommended for this application.
My previous cabin, which is now rental property, has the same 10gal electric heater. Its been in constant use for 13 years. Sure, I've replaced a couple of heating elements, but they only cost about $8 apiece and take about 20 minutes to change when they fail.
Tom
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larry
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# Posted: 27 Dec 2012 07:48
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i looked at a on demand system and after trying to actually buy one from the local supply store i could not find one. i was told by the locals that "very few people use them in this area because the water is too hard and the manufacturers wont warranty them when they plug up". I'm using well water with a great deal of iron in it. on a brighter note, my hi efficiency propane water heater uses very little propane and i could not be happier.
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