On-demand hot water heaters

Darren Wright

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My hot water heater has been going out about every other day. I've replaced the thermocouple with two different brands and is still happening. I think I've determined that the gas valve is going bad. It's about 6 years old and not sure that it's worth replacing just the gas valve ($150 new/discontinued) as it's not great quality.

It also sits right in front of our Washer, so to gain some real estate in the laundry room, we've been considering the tank-less on-demand models.

I'm just not sure how many gallons per minute I should consider. We've got 2 full baths and may run the washer (high efficiency) and dishwasher about the same time of day as taking showers, but rarely both at the same time.

So does anyone have a tank-less natural gas unit, if so, what brand? how many gpm? what is you're review of it?

Thanks :wave:
 
Don't but a few things we found when looking and talking to friends about them:

They take a fairly good sized gas line. Ours wasn't big enough to drop in, I think a 3/4" line was the smallest we could find (this was 3? years ago or thereabouts). That's mainly why I don't have one today because the gas feed line to that side of the house was only 1/2" :D

A friend got one and "up sized" it a little to much. Apparently it had a flow rate threshold for kicking on and their low flow shower wasn't sufficient to make it turn on. So when you took a shower at his house you'd have to crack the hot water on in the sink or you'd never get a hot shower. I think some of the newer ones are smarter than this (and he also bought one that was basically "hotel" sized which was wayyy to big).
 
I have only 3 choices to heat hot water

1) Propane --- NO - not the way to go
2) Electricity - I did think about it
3) Oil - that is what heated the water here for years - and that is what I choose.

I had in the furnace tankless hot water. That developed into a host of problems.

What I chose to do was to install what is called an indirect hot water tank. In my situation, it just came out as my best option. It is a separate hot water storage tank that gets it's source of heat from the furnace via a separate "zone". The aquastat draws heat from the furnace as needed to maintain the water in the storage tank. Coupled with a high efficiency furnace it is competitive with just about any other source of hot water. I do NOT have a high efficiency furnace - YET.

I did the install of the indirect hot water heater, including adding a 3-rd zone the the existing furnace. I also added in some whole house filters. All together it took 1-1/2 days for the installation. I was alone with no help.

Indirect hot water can be coupled with any furnace that makes hot water - as in baseboard hot water heat.

I did give thought to the on demand hot water, but that would have had to be Propane. I don't know if you know this - but Propane is normally very expensive - except for this year - it is 3x more expensive than normally expensive. Not a good source of heat.

I LOVE - the indirect hot water. I will recommend it as a valid choice for hot water.

My oil consumption has been reduced by 50-60%
 
We have had the Rockstar treatment with water heaters...except for the last house :(. For the last 15 years we've had tankless from Rinnai (http://www.rinnai.us/tankless-water-heater/). Tell it when to go on and when to go off..."Fast Start" button if you get sprayed by a skunk!! Metered water being what it is in the US now...hard to beat. We have always had the gas fired model...they are great! More, not much...but more standard maintenance, but nothing a beer wont fix ;)
 
Yep the Rinnai units rock, that is just about all we have here in Tokyo, they really do work well, I would not want anything else.

When we had two daughters in the house I could still get a nice hot shower after they both had their showers. Our main unit in the house has a nice feature, you can crank the temp up to 60C/140F if you want, this is great for cleaning some things, you can get HOT water! Usually we keep it at 43C/109F. Our unit is not really comparable to what you would get in the US, it runs the kitchen, and the bathtub room too, and it can fill the tub with hot water at the touch of one button, and it can reheat water from the tub too, I doubt you can buy that in the US.

Love these units, way cheaper to us natural gas here than electricity too.

Cheers!
 
We just went thru this thought process and settled on a hybrid hot water heater. It is installed in our walkout basement. Our pellet stove is there as well so plenty of heat in the winter for the heat pump to do it's thing. There are 4 of us, 2 adults, a teenager, and our soon to be adopted 7 year old. Works great so far. Reviews are all over the map online but we thought it was worth a gamble.

http://products.geappliances.com/ApplProducts/Dispatcher?REQUEST=SpecPage&Sku=GEH50DEEDSR
 
Consider checking with your electric company. Some have lease or sale plans for high efficiency water heaters. As for the on-demand types. I have heard good and bad reports from those who have them. My son has one and it takes forever for hot water to get to the faucet. A friend has one and loves it. Before I would get one I would do a lot of homework.:huh:
 
..............................................
What I chose to do was to install what is called an indirect hot water tank. In my situation, it just came out as my best option. It is a separate hot water storage tank that gets it's source of heat from the furnace via a separate "zone". The aquastat draws heat from the furnace as needed to maintain the water in the storage tank. Coupled with a high efficiency furnace it is competitive with just about any other source of hot water. .........................

I LOVE - the indirect hot water. I will recommend it as a valid choice for hot water.

I have the same system as Leo. Very responsive, simple design, works very well & is cost efficient.

Like any other system, when turning on the hot water faucet all the cold water in the line must exit before the hot water arrives. I think that in itself is an opportunity for a great invention to save all that wasted cold water. Have given thought to the cold water being redirected for recycling purposes (until the hot water arrives), but haven't come up with a viable solution.
 
I have a tankless unit. for us, it was a necessity.
My house is a tiny cape. The hoter water heater and tank was behind my fridge, so accessing it whenever was a disaster, and ruined many kitchen floors
Once we converted, its just a box on the wall, and it works great, all the hot water you want.
We still have to turn down the heat first when its in the teens to get quick demand to our shower(we have 3 heating zones, and although domestic water is supposed to come first, seems it lags for a bit, and we want it instantly)
Its a lot better than the previous heating system we had here.
I couldn't tell you a thing about it, as Im not familiar with that kind of stuff.
works great, we can run a washing machine and take showers continuously, even 2 showers at a time.
 
Like any other system, when turning on the hot water faucet all the cold water in the line must exit before the hot water arrives. I think that in itself is an opportunity for a great invention to save all that wasted cold water. Have given thought to the cold water being redirected for recycling purposes (until the hot water arrives), but haven't come up with a viable solution.

They have these systems that recirculate the hot water that is supposed to address the issue.

Don't know much about them other than having seen them on some of the home improvement shows. Supposedly, they can work with existing plumbing, but I'd think a dedicated return line would probably be better.

Hot_Water_Recirculation_Process.gif

 
Recirculating systems like Brent showed are not uncommon in commercial/public buildings. I've worked on some projects where they were installed as part of new construction, but I don't recall any details about their cost effectiveness. They save water since people no longer run the tap while waiting for the hot water to arrive, but they require twice the amount of plumbing (and it really should be well-insulated), and there is some heat loss in pushing hot water back and forth all over the building.
 
We plumbed in a hot water recirc pump when we built in '2005. No regrets. It works great and the plumber told me you can buy a rebuild kit for small money if the little pump ever quits. Another thing we did, because the hot water tank is in the attic, was to add a gizmo that detects water in the pan under the tank and shuts off both the water and the gas when the inevitable leak occurs. Glad we did because 6 months after we moved in the hot water shut off and we discovered a big leak at the tank. The gizmo worked as advertised and the plumber replaced it on his dime because the leak was his fault (made a bad connection).
 
They have these systems that recirculate the hot water that is supposed to address the issue.

Don't know much about them other than having seen them on some of the home improvement shows. Supposedly, they can work with existing plumbing, but I'd think a dedicated return line would probably be better.

View attachment 81498


Thanks Brent, that was really good feedback. :thumb: Will be looking into that as it will not only eliminate the wait for hot water, it will reduce the loss of good water, and will totally minimize the drainage into the septic system.
 
A little late to the party, but I'll weigh in.

We put a natural gas Rinnai unit in our house when we built in 2006. It powers the laundry and both bathrooms. I had an almost new tank unit that I used in the new house to power the kitchen. If I recall the big unit has a rate of around 6-7 gallons per minute. Both showers have reduction shower heads that only allow 2 gallons per minute to flow as I recall. We have used both showers at once several times and everyone had hot water. There is a short period of cold water in the first shower when the second is turned on though, but you can stand in there all day taking a hot shower. It also fills our Jacuzzi tub and doesn't run out of hot water.

About two years ago the tank unit went out so I got another smaller Rinnai for the kitchen. It handles 4-5 gallons per minute as I recall and is plenty for the dishwasher and sink.

They are more $$ initially but the energy savings and long life will pay that money back pretty quick I think. I've heard they will last upwards of 20 years if maintained properly.
 
Just to follow through on my initial response - cross checked (and book marked :thumb:) the Rinnai's and they all (for some small value of "all" at least the ones I looked at...) appear to require a 3/4" gas line and have a minimum activation flow rate of 0.4GPM. Very reasonable (I wish they'd put a bigger gas line into the garage when they ran it for our hot water heater).
 
Darren, you can look up my unit online. Ny Thermal t-200, their website has all the info on it. I went an looked for my installation manual for you, but the website has everything you would want to know.
 
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