I plan to purchase a tankless water heater to replace a failing water
tank.   The current vent is a 6" diameter vent pipe.  I need a 7.4 GPM
unit (4 bathroom house with 3 showers) and considering a Rheem
GT199PVN.   I noticed some tankless heaters have two separate vent
pipes (one intake and the other exhaust).  Some have one vent pipe
with one pipe inside the other.  If I choose the later I will need an
additional hole in the side of the house (no chimney).  What are the
pros and cons of two separate pipes than just one pipe with an
interior pipe?    Are two separate pipes functionally better than one
pipe inside the other?  I'm a bit concerned when I need to replace the
new heater (hopefully in 10+ years) that I may have to deal with
patching or resizing holes.   I've seen so many different kinds and
configurations in water heaters and vents.  Unemployed right now, I
don't have $1600 to spend on installation, I got the time to do it
myself.  Any tips on installation are appreciated.

On 2009-08-06, Phisherman <n...@noone.com> wrote:

> I plan to purchase a tankless water heater to replace a failing water
> tank.

I am definitely a fan of tankless water heaters, but one alternative
to consider is a condensing tank water heater.  It will be even more
efficient than a non-condensing tankless water heater.  One issue is
that a condensing tank will cost a lot more than a non-condensing
tankless, and while that is often offset by less installation labor
for the condensing tank, since you said you'd be installing it
yourself, that wouldn't apply.

> I need a 7.4 GPM unit (4 bathroom house with 3 showers) and
> considering a Rheem GT199PVN.

A couple comments.  That GT199PVN won't really provide you with 7.4
GPM of hot water--that flow rate is for only a 45 degree Fahrenheit
temperature rise.  It's mainly a marketing exaggeration, it would only
apply if your incoming cold water is 60 degrees already and you are
happy with 105 degree hot water.  Where are you located?  If your
incoming water is actually 50 degrees, and you want 110 degree water
in your shower, then that's a temperature rise of 60 degree, so you'd
get about (45/60) * 7.4 = 5.55 gpm.

Another comment is that 7.4 GPM (if you get a bigger unit that can
handle it) is enough for three simultaneous uses, e.g. 3 showers, or 2
showers and a dishwasher, 2 showers and 2-3 vanities, etc.  Depending
on your lifestyle and how many people are in your house, then 2
simultaneous uses might be enough, in which case the GT199PVN is
likely to be adequate (depending on where you live and the incoming
cold water temperature).

> What are the pros and cons of two separate pipes than just one pipe
> with an interior pipe?  Are two separate pipes functionally better
> than one pipe inside the other?

Good question, I don't know if separate pipes is a functionally better
arrangement, but it certainly seems like a combined pipe is more
convenient.

Cheers, Wayne

"Ralph Mowery" <r...@earthlink.net> wrote in message 
news:I...@earthlink.com...
>
> "Phisherman" <n...@noone.com> wrote in message 
> news:s...@4ax.com...
>>I plan to purchase a tankless water heater to replace a failing water
>> tank.   The current vent is a 6" diameter vent pipe.  I need a 7.4 GPM
>> unit (4 bathroom house with 3 showers) and considering a Rheem
>> GT199PVN.   I noticed some tankless heaters have two separate vent
>> pipes (one intake and the other exhaust).  Some have one vent pipe
>> with one pipe inside the other.  If I choose the later I will need an
>> additional hole in the side of the house (no chimney).  What are the
>> pros and cons of two separate pipes than just one pipe with an
>> interior pipe?    Are two separate pipes functionally better than one
>> pipe inside the other?  I'm a bit concerned when I need to replace the
>> new heater (hopefully in 10+ years) that I may have to deal with
>> patching or resizing holes.   I've seen so many different kinds and
>> configurations in water heaters and vents.  Unemployed right now, I
>> don't have $1600 to spend on installation, I got the time to do it
>> myself.  Any tips on installation are appreciated.
>
> While you are at it ,  does the gas supply have enough capacity to run the 
> water heater ?
> I still think it is cheaper to just run the old style tank in the long 
> run.
>
>

I agree...Especially with 4 bathrooms , 3 showers , dishwasher , sinks , 
ect....Would have to be a big tankless unit with a huge gas pipe or large 
electrical service , if electric , which would require an upgrade for the 
gas or electric service...And your unemployed to boot....Get the old style 
tank and hook it up yourself without the major upgrades....Cheap and easy 
and not really that much more to run....... 

"Phisherman" <n...@noone.com> wrote in message 
news:s...@4ax.com...
>I plan to purchase a tankless water heater to replace a failing water
> tank.   The current vent is a 6" diameter vent pipe.  I need a 7.4 GPM
> unit (4 bathroom house with 3 showers) and considering a Rheem
> GT199PVN.   I noticed some tankless heaters have two separate vent
> pipes (one intake and the other exhaust).  Some have one vent pipe
> with one pipe inside the other.  If I choose the later I will need an
> additional hole in the side of the house (no chimney).  What are the
> pros and cons of two separate pipes than just one pipe with an
> interior pipe?    Are two separate pipes functionally better than one
> pipe inside the other?  I'm a bit concerned when I need to replace the
> new heater (hopefully in 10+ years) that I may have to deal with
> patching or resizing holes.   I've seen so many different kinds and
> configurations in water heaters and vents.  Unemployed right now, I
> don't have $1600 to spend on installation, I got the time to do it
> myself.  Any tips on installation are appreciated.

While you are at it ,  does the gas supply have enough capacity to run the 
water heater ?
I still think it is cheaper to just run the old style tank in the long run.

Wayne Whitney <w...@post.harvard.edu> wrote:

>Another comment is that 7.4 GPM (if you get a bigger unit that can
>handle it) is enough for three simultaneous uses

And will likely require a larger utility service (electrical or gas), making the
economics worse.

On Thu, 6 Aug 2009 13:06:41 -0500, "Ralph Mowery"
<r...@earthlink.net> wrote:

>
>"Phisherman" <n...@noone.com> wrote in message 
>news:s...@4ax.com...
>>I plan to purchase a tankless water heater to replace a failing water
>> tank.   The current vent is a 6" diameter vent pipe.  I need a 7.4 GPM
>> unit (4 bathroom house with 3 showers) and considering a Rheem
>> GT199PVN.   I noticed some tankless heaters have two separate vent
>> pipes (one intake and the other exhaust).  Some have one vent pipe
>> with one pipe inside the other.  If I choose the later I will need an
>> additional hole in the side of the house (no chimney).  What are the
>> pros and cons of two separate pipes than just one pipe with an
>> interior pipe?    Are two separate pipes functionally better than one
>> pipe inside the other?  I'm a bit concerned when I need to replace the
>> new heater (hopefully in 10+ years) that I may have to deal with
>> patching or resizing holes.   I've seen so many different kinds and
>> configurations in water heaters and vents.  Unemployed right now, I
>> don't have $1600 to spend on installation, I got the time to do it
>> myself.  Any tips on installation are appreciated.
>
>While you are at it ,  does the gas supply have enough capacity to run the 
>water heater ?
>I still think it is cheaper to just run the old style tank in the long run.
>


I'm in e.TN. Two adults in the house.  The cold water is warm enough
to shower without being heated, although somewhat uncomfortable.   An
old-style tank is about $990 (Rheem direct vent), and a tankless about
$1400 (or $1200 if I order online).  

On Aug 6, 7:48=A0am, Phisherman  wrote:

>snip<

 =A0Unemployed right now, I don't have $1600 to spend on installation, I
got the time to do it
> myself. =A0Any tips on installation are appreciated.

Wouldn't tit be wise to get the cheapest useable heater right now and
wait to see how your job situation goes with respect to the
Obamanomics turmoil right now? Unless you're running a Bed 'N
Breakfast, closing off a bathroom or two doesn't seem like much of a
sacrifice to keep the family finances afloat. Whatever, good luck.

Joe

On Thu, 06 Aug 2009 14:42:48 -0400, Phisherman <n...@noone.com>
wrote:

>On Thu, 6 Aug 2009 13:06:41 -0500, "Ralph Mowery"
><r...@earthlink.net> wrote:
>
>>
>>"Phisherman" <n...@noone.com> wrote in message 
>>news:s...@4ax.com...
>>>I plan to purchase a tankless water heater to replace a failing water
>>> tank.   The current vent is a 6" diameter vent pipe.  I need a 7.4 GPM
>>> unit (4 bathroom house with 3 showers) and considering a Rheem
>>> GT199PVN.   I noticed some tankless heaters have two separate vent
>>> pipes (one intake and the other exhaust).  Some have one vent pipe
>>> with one pipe inside the other.  If I choose the later I will need an
>>> additional hole in the side of the house (no chimney).  What are the
>>> pros and cons of two separate pipes than just one pipe with an
>>> interior pipe?    Are two separate pipes functionally better than one
>>> pipe inside the other?  I'm a bit concerned when I need to replace the
>>> new heater (hopefully in 10+ years) that I may have to deal with
>>> patching or resizing holes.   I've seen so many different kinds and
>>> configurations in water heaters and vents.  Unemployed right now, I
>>> don't have $1600 to spend on installation, I got the time to do it
>>> myself.  Any tips on installation are appreciated.
>>
>>While you are at it ,  does the gas supply have enough capacity to run the 
>>water heater ?
>>I still think it is cheaper to just run the old style tank in the long run.
>>
>
>
>I'm in e.TN. Two adults in the house.  The cold water is warm enough
>to shower without being heated, although somewhat uncomfortable.   An
>old-style tank is about $990 (Rheem direct vent), and a tankless about
>$1400 (or $1200 if I order online).  

Here is nice guide with some venting information.*

Exterior tankless heaters are not required to have outside venting,
iirc.

If I was building "new" there would tankless installed. A local fire
captain built a 5,000 sf home. He installed 3 tankless heaters,
configured in "zones". One for the laundry, kitchen and garage (inside
garage) Two exterior units at opposite ends of the house. His three
daughter-units have one (3 BR, 3B)

The MBR, Bath and Powder room have one heater on their side of the
house (exterior)

*
http://www.tanklesswaterheaterguide.com/

just wait for a storm and power failure, with tankless no hot water at
all......

the vertex condensig qualifies for the 30% tax break.

On Thu, 6 Aug 2009 13:19:56 -0700 (PDT), bob haller <h...@aol.com>
wrote:

>just wait for a storm and power failure, with tankless no hot water at
>all......
>

Not with gas units. They have a spark igniter - just like your gas
grill. Gas works when the power is out!

>the vertex condensig qualifies for the 30% tax break.

So does my new  garage door.