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Get Rid of Your Hot Water Tank?


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#1 of 35 OFFLINE   Jay Taylor

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Posted May 04 2005 - 02:12 AM

Our hot water tank needs to be replaced and we’re considering getting rid of the tank and replacing it with an endless hot water system, such as a Rinnai.

We currently have a large whirlpool tub at the opposite end of the house from the hot water heater. It will only fill the tub one half way before there’s no more hot water. So three options we are considering is to go from a 40 gallon gas hot water heater to an 80-100 gallon commercial gas hot water heater, or get a 50 gallon quick recovery tank, or to eliminate the tank and get a Rinnai endless hot water system.

Do any of you have experience with a Rinnai or something similar?

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#2 of 35 OFFLINE   Andrew Grall

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Posted May 04 2005 - 02:35 AM

I've heard of those kinds of units before...

How much do they cost?

#3 of 35 OFFLINE   Jay Taylor

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Posted May 04 2005 - 02:43 AM

How much do they cost?

Typically over $3,000.00 counting installation, in part due to the requirement of installing a stainless steel vent pipe through the roof.

That's a lot of money to replace a hot water tank! On the good side, your gas or electric bill should be significantly lowered because you're not heating a water tank 24 hours a day.
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#4 of 35 OFFLINE   RobertR

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Posted May 04 2005 - 03:19 AM

This article made me decide not to get a tankless water heater:

http://www.askthebui....ng_Facts.shtml

#5 of 35 OFFLINE   Jay Taylor

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Posted May 04 2005 - 04:14 AM

Thanks for the link Robert.

Since I don’t have kids many of the arguments he raised against the tankless systems are not an issue at our home. I bet he’s right about exceeding flow capacity if you have a washing machine going while filling a tub in the winter when incoming water temperature is near 40 degrees.

My main goal is to be able to fill the whirlpool tub with hot water. We’ve ignored this “fun” tub and just used showers or other tubs for five years because our 40-gallon water tank will only fill it half way before the water goes cold. The tankless system seems like a workable solution.

I wonder if a quick recovery 50-gallon tank would fill the whirlpool tub with hot water?
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#6 of 35 OFFLINE   RobertR

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Posted May 04 2005 - 04:22 AM

Jay:

From what I understand, tankless heaters are sometimes used for a single application. If you dedicate one to your whirlpool tub, that might make the most sense. I would spend much less than $3000, though...more like $1000. I don't know if the quick recovery 50-gallon tank would do the job.

#7 of 35 OFFLINE   Dennis*G

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Posted May 04 2005 - 04:26 AM

Maybe install 2 50 gallon water heaters? I could be talking out my butt (I've done that many times) but maybe just have a second unit on reserve, maybe turn the gas onto it only on the weekends (or whatever day you may use the whirpool)

#8 of 35 OFFLINE   Jay Taylor

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Posted May 04 2005 - 06:11 AM

From what I understand, tankless heaters are sometimes used for a single application.
I used to live in Italy where they frequently used small electric tankless heaters for a single application such as the kitchen or bathroom. Because they were electric they had no problems with venting that gas heaters have. The electric ones didn't have much capacity though.

Having an external gas tankless heater mounted on the opposite side of the house for the whirlpool tub would probably be expensive.

Maybe install 2 50 gallon water heaters?
This was going to be my first choice but unfortunately if I installed two tanks in the garage closet I wouldn't have room to access the central air system (which will probably be the next thing to break.) Posted Image
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#9 of 35 OFFLINE   Al.Anderson

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Posted May 04 2005 - 06:47 AM

Don't know if this is the same thing you're talking about or not; but I have a hot water heater system as part of my house heater. (Oil based / baseboard) I absolutely love it! I would pay extra to never have to go back to a hot water heater in any future house. There are four of us (two kids) and we've never run into a flow problem with competition from the clothes washer, etc.

#10 of 35 OFFLINE   Joe Szott

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Posted May 04 2005 - 07:23 AM

I would think that if the 40 gallon heater was good enough for everything except the 100 gallon tub, then putting in a 100 gallon heater would be a bit wasteful. After all, what if you drifted away from using the tub again and were then stuck with this massive heating tank?

Something to consider would be to split the difference. Get a 50 gallon tank for the home, then install a smaller electric heater just on the tub line. That way you could pull medium hot water from the cold/hot lines of your house and have the smaller electric heater pull that temp up to hot before it hits the tub. The 50 gallon tank lasts to 100 gallons since you aren't pulling as much hot water so quickly, and when not using the tub your heating bill won't be so inflated.

Just an idea, don't really know if that would work or not.

#11 of 35 OFFLINE   Ron-P

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Posted May 04 2005 - 09:09 AM

Living in earthquake land I'd never get a tankless water heater, I like have a 50+ gallon water supply readily available, just in case.
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#12 of 35 OFFLINE   Jay Taylor

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Posted May 04 2005 - 09:30 AM

Another company’s tankless system that we’re considering is by Bosch. The Bosch produces 175,000 BTU/H and the Rinnai 180,000 BTU/H.

Motivated by Robert’s link I did some checking on sustainable flow rates based on the amount of increase in water temperature required. Here’s the data for the Bosch:

45 Degree Rise @ 6.4 gallons per minute
55 Degree Rise @ 5.3 gallons per minute
65 Degree Rise @ 4.5 gallons per minute
75 Degree Rise @ 3.9 gallons per minute
90 Degree Rise @ 3.3 gallons per minute

A typical shower uses 2.5 gallons per minute and a high flow shower may be much more.

So if it’s the middle of winter in North Dakota, you’re water temperature is 40 degrees Fahrenheit and you want a 105 degree shower, it can sustain 4.5 gallons per minute or 3.9 gallons per minute for a 115 degree shower.

This means that you wouldn’t want to turn on the washing machine or hot water faucets when taking a shower while the incoming water temperature is that low or your shower temperature will drop. In the summer it will be less of a problem.
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#13 of 35 OFFLINE   Jay Taylor

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Posted May 04 2005 - 01:44 PM

Here's another interesting article. It claims that tankless water heaters dominate the European and Asian markets.

Going Tankless
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#14 of 35 OFFLINE   Dave Poehlman

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Posted May 04 2005 - 03:21 PM

Quote:
It claims that tankless water heaters dominate the European and Asian markets.


I don't think they're necessarily new over there. When I was in Prague in '96 the B&B we stayed at had a rather antiquated thing hanging on the wall above the tub. While you were showering, the thing would kick in with a big "whoosh!" and you could see blue gas flames inside.

It sounds like someone has actually made them efficient.

I'm skeptical about the actual savings vs a tank. I think a moderately efficient tank will keep water warm for quite some time once heated. I can't imagine it has to kick in much more than once or twice a day when unused. But perhaps I'm just naive when it comes to my water heater.

#15 of 35 OFFLINE   Jay Taylor

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Posted May 05 2005 - 10:16 AM

After checking out many options, we decided upon the Bosch Pro Tankless 635 ES. It produces 175,000 BTU/H and with the water temperature in Oklahoma City it will have sufficient flow for a shower and a sink to run simultaneously.

Two of the contractors making bids had this unit. Their natural gas bill is higher because their teenagers spend too much time in the hot showers. It never runs out of hot water! Luckily I don't have kids.

I'll let you know what I think of the unit after it's installed.

This is it:

Bosch Pro Tankless 635 ES
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#16 of 35 OFFLINE   Dave Poehlman

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Posted May 05 2005 - 01:41 PM

Can we ask how much it was, Jay?

#17 of 35 OFFLINE   Philip_G

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Posted May 05 2005 - 02:56 PM

I wanted to get a tankless but just couldn't afford it, let us know how you like it!

#18 of 35 OFFLINE   Jay Taylor

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Posted May 05 2005 - 03:49 PM

$2,685.00

Here's why:

You can find a tankless system capable of 175,000 BTU/H for around $1,000.00. The $400.00 to $500.00 units I’ve seen for sale are low flow units that will not meet the needs of most households except for a single function such as your laundry room.

The tankless systems require a stainless steel ducting system that typically runs about $250.00 to $300.00 uninstalled.

Our old hot water heater had ducting tied in with the central air system with a type of ducting that is no longer up to code. Each of the three tankless contractors giving me estimates concluded that the ducting to the central air system would have to be replaced rather than plug the input from the old water tank. I don’t know how much that ducting cost.

To meet current code requirements both the Rinnai and the Bosch require the installation of an air intake pipe from outside of the water heater closet. Apparently this requirement is a result of heating systems drawing in fumes from garages and presenting an explosion or flame hazard.

The Rinnai accomplishes this by having a very expensive stainless steel dual pipe going through the ceiling, through the attic & roof. The inner tube of the pipe is the exhaust, and the outer tube of the pipe is the air intake from outside.

The Bosch accomplishes this by having a PVC pipe go through the ceiling of the closet into the attic and making a 180-degree turn in the attic so things won’t fall down the pipe.

So the Rinnai air intake comes from outside and the Bosch air intake comes from the attic.

The exhaust from both the Rinnai and the Bosch must exit via stainless steel ducts through the ceiling, the attic and the roof. For both units the roof shingles are pulled back, a hole is cut in the ceiling and roof, the pipe installed, the flashing installed & sealed, then the shingles sealed back into place.

The natural gas line to a tankless system needs to be larger than the line we had going to the hot water heater. The old gas line to the central air system would be in the middle of the closet once we got rid of the old hot water heater. So part of the contract was to replace the gas line to the central air system to an out of the way location. Part of the contract was to route a larger gas line from the attic to the Bosch.

The incoming and outgoing water lines and valve needed replacing to make the installation neater.

A significant part of the total was labor but I’m not sure how much.

Like most cities, Oklahoma City requires everything to be installed to code including the changes to the central air system because a city inspector must sign off on the installation.

So it’s nice to dream about getting a high capacity tankless system up and running for $1,000.00 but unless you happen to have stainless steel ducts, fittings, flashing, and gas & water pipe fittings lying around, and are willing to do all of the labor yourself, it’s not going to happen.

The contractor believes that he can do the entire installation tomorrow. We’ll see!
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#19 of 35 OFFLINE   Philip_G

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Posted May 05 2005 - 04:28 PM

Probably used single wall B-Vent in a non heated space and it needs to be double wall Jay.
it's not all that costly to do.

#20 of 35 OFFLINE   Jay Taylor

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Posted May 06 2005 - 02:04 AM

Probably used single wall B-Vent in a non heated space and it needs to be double wall Jay.

Yes Philip, that's what our previous water heater and central air used. The hot water heater duct was attached to the central air duct with a "Y". I was told that if you connected a tankless heater to one of those ducts it would melt!

They are going to replace the central air duct with a double wall duct, and the tankless heater will have a stainless steel duct for exhaust and PVC for air intake.

Prices quoted from other companies making the same corrections were:

$3,489.00 for the same Bosch installation.
$3,889.00 for a Rinnai Continuum 180,000 BTU/H.
$3,085.00 for a Rinnai Continuum 180,000 BTU/H.

I saw in one of the contractors catalogs that the Bosch 635 ES was listed as $1,800.00 - $1,950.00 depending on how preferred the customer is. But I'm guessing they are paying closer to $1,000.00 for the unit.

The company that quoted $2,685.00 had the most experience and knowledge with waterless tanks and had a reputation as good as the others.

Due to problems with shoddy work from contractors in the past I didn't bother contacting plumbers without significant experience with these units. I'm sure Joe Buttcrack Plumbing would have done the job cheaper but I didn't want a leaky roof followed by a burned down home. Posted Image
"Any sufficiently advanced technology is indistinguishable from magic." - Arthur C. Clarke