I have a 50Gal hot water heater under my house serving 2 bathrooms and
four people. I am looking for a safe way to prolong the availability of
hot water when two or three people take a shower in a row. I was
thinking about putting an inline water heater before the 50gal tank
heater. I don't want to buy a big inline heater, as it's just going to
be for stretching out the hot water available during a 40 minute
period. The problem I see is the max flow through the inline unit will
be too small. Do they make inline units that will flow at arbitrary
rates, and just heat the water less when flowing fast? This would be
ideal for me. Otherwise, could I split the flow (in parallel) going
into the tank water heater: half through the inline unit, and 2) half
through some restrictor valve to even the bias?

You could get a tankless to do the whole job, a Takagi or Rinnai then
you can realy waste water and let everyone take 40 minute showers, since
cost is not an issue for you.

Go tankless.

cm
wrote in message
ups.com...
I have a 50Gal hot water heater under my house serving 2 bathrooms and
four people. I am looking for a safe way to prolong the availability of
hot water when two or three people take a shower in a row. I was
thinking about putting an inline water heater before the 50gal tank
heater. I don't want to buy a big inline heater, as it's just going to
be for stretching out the hot water available during a 40 minute
period. The problem I see is the max flow through the inline unit will
be too small. Do they make inline units that will flow at arbitrary
rates, and just heat the water less when flowing fast? This would be
ideal for me. Otherwise, could I split the flow (in parallel) going
into the tank water heater: half through the inline unit, and 2) half
through some restrictor valve to even the bias?

cm wrote:
Go tankless.


AND HAVE TROUBLES! Low flow no hot water, power failure no hot water,
need to upgrade power or gas lines and perhaps still no be happy

Another option is a tempering valve.

you set the existing hot water tank to HOT and install a tempering
valve at the outlet.

it mixes hot with cold water so you cant get scalded. acts like a
larger hot water tank.

-----------------------------------------------------------------------------------------------------------

a tankless before your hot water tank will help, low flow doesnt matter
since you only need the extra capacity during high flow periods.

at low flow times the existing hot water tank can easily keep up with
demands

I ended up buying a high BTU tank. its 50 gallons at 75,000 BTU. This
solved my running out of hot water trouble.

I always shower before laundry but then we have 2 washing machines, so
demands can get high........

why would max demand be low flow?

max demand is when the tankless will be of most help?

are you talking electric or gas?

My concern is that my current tank water heater will let through, lets
just say for argument sake, 10gpm, and by putting an inline in front of
it, the inline will only let through, say, 3gpm, thus my whole hot
water system will be throttled back to 3gpm. I want to know if small
inlines are limited to a certain flow, or if the flow rating is just a
number that guarentees full heating if the flow is not higher.

I don't want to buy a full size inline water heater since i have a new
regular water heater, and I only want to buy a small inline to put in
front of it,to save money on equipment costs, and to boost the hot
water system a little.

wrote:
My concern is that my current tank water heater will let through, lets
just say for argument sake, 10gpm, and by putting an inline in front of
it, the inline will only let through, say, 3gpm, thus my whole hot
water system will be throttled back to 3gpm. I want to know if small
inlines are limited to a certain flow, or if the flow rating is just a
number that guarentees full heating if the flow is not higher.

snip.
-------------------------------------------------------------------------------------------
The way I understand it -- and I might be wrong so I'm open to comment
-- is that an tankless unit has a rated flowrate that indicates its
maximum efficiency. IOW, it might be rated at 3gpm, but will actually
allow 10gpm to pass through it -- just not as hot.

I THINK I know what I'm trying to say here -- hope it makes sense to
someone else.

Mark

wrote:

I have a 50Gal hot water heater under my house serving 2 bathrooms and
four people. I am looking for a safe way to prolong the availability of
hot water when two or three people take a shower in a row...

You might look into a greywater heat exchanger, or check out

http://www.sunfrost.com/efficient_shower.html

Nick

Mark, that is exactly what I want to know. if you are right, then I
should be able to put a small, single room, in-line unit before my hot
water heater, and during peak hot water usage, still have enough hot
water for everyone to take showers. I wonder how much more in
electricity this type of set up will run me?

Mark Sparge wrote:
wrote:
My concern is that my current tank water heater will let through, lets
just say for argument sake, 10gpm, and by putting an inline in front of
it, the inline will only let through, say, 3gpm, thus my whole hot
water system will be throttled back to 3gpm. I want to know if small
inlines are limited to a certain flow, or if the flow rating is just a
number that guarentees full heating if the flow is not higher.

snip.
-------------------------------------------------------------------------------------------
The way I understand it -- and I might be wrong so I'm open to comment
-- is that an tankless unit has a rated flowrate that indicates its
maximum efficiency. IOW, it might be rated at 3gpm, but will actually
allow 10gpm to pass through it -- just not as hot.

I THINK I know what I'm trying to say here -- hope it makes sense to
someone else.

Mark

wrote:
wrote:

I have a 50Gal hot water heater under my house serving 2 bathrooms and
four people. I am looking for a safe way to prolong the availability of
hot water when two or three people take a shower in a row...

You might look into a greywater heat exchanger, or check out

http://www.sunfrost.com/efficient_shower.html

Nick


The whole point of putting a tankless in series with a tank type heater
escapes me. Once the 50 gals of hot water in the tank is gone, for
the tankless to be of any significant benefit, it's going to have to
have enough capacity to pretty much heat the incoming water up to full
temp. This means a gas fired unit of sufficient capacity. Once you
have that, what's the point to having the tank heater too? It just
defeats one of the main features of the tankless, which is no standby
loss of heat from the tank.

And forget the greywater heat exchanger, as you're never going to
recover enough heat from tepid water going down the drain to heat
incoming fresh cold water anywhere near to the point of it being
usable. Just more pie in the sky ideas, without regard to the real
world.

wrote:

And forget the greywater heat exchanger, as you're never going to
recover enough heat from tepid water going down the drain to heat
incoming fresh cold water anywhere near to the point of it being
usable. Just more pie in the sky ideas, without regard to the real
world.

You sure about that? The DOE seems to think it works.

I just did a quick google and one of them (GFX) claims over 60% heat
extraction from drainwater. If you've got hot water from a shower going
down the drain that could make a difference even if you assume that
they're exaggerating.

Apparently it can preheat the water coming into the water heater by
20-30 degrees.

Chris

"The whole point of putting a tankless in series with a tank type
heater
escapes me. Once the 50 gals of hot water in the tank is gone, for
the tankless to be of any significant benefit, it's going to have to
have enough capacity to pretty much heat the incoming water up to full
temp. This means a gas fired unit of sufficient capacity. Once you
have that, what's the point to having the tank heater too? It just
defeats one of the main features of the tankless, which is no standby
loss of heat from the tank. "

I agree with the above station. I also think the OP is being a big
baby. If they want to have hot water under low flow conditions,
presumably they are thinking of a situation where they are, for
example, washing their hands, then maybe they should try using a
separate inline water heater at the sink itself.

The whole point of putting a tankless in series with a tank type heater
escapes me. Once the 50 gals of hot water in the tank is gone, for
the tankless to be of any significant benefit, it's going to have to
have enough capacity to pretty much heat the incoming water up to full
temp. This means a gas fired unit of sufficient capacity. Once you
have that, what's the point to having the tank heater too? It just
defeats one of the main features of the tankless, which is no standby
loss of heat from the tank.

And forget the greywater heat exchanger, as you're never going to
recover enough heat from tepid water going down the drain to heat
incoming fresh cold water anywhere near to the point of it being
usable. Just more pie in the sky ideas, without regard to the real
world.

Well a small single faucet 200 buck unit probably wouldnt help at all


but any raise in incoming water temp will yield more hot water...

witha new hot water heater adding a tempering valve and setting btank
to max will help some

the OP should of purvhased a high BTU tank for greater recovery.

if theres space adding a second regular tank in series should fix his
problem./

frankly i HATE running out of hot water!

wrote:
Mark, that is exactly what I want to know. if you are right, then I
should be able to put a small, single room, in-line unit before my hot
water heater, and during peak hot water usage, still have enough hot
water for everyone to take showers. I wonder how much more in
electricity this type of set up will run me?

--------------------------------------------------------------------------------------
I'd probably be tempted to go a bit larger than the minimum, just
because of the increased flow-rate capability. Any amount you can
raise the temperature into the big tank will be a savings -- though
there may be some point of diminishing returns. You will probably
raise your electric bill some with the tankless, but certainly less
than if you put another tank-type in line with the existing heater.

Marrk

wrote:

... forget the greywater heat exchanger, as you're never going to
recover enough heat from tepid water going down the drain to heat
incoming fresh cold water anywhere near to the point of it being
usable.

Try a few real numbers, vs faith :-)

Nick

wrote:

The whole point of putting a tankless in series with a tank type heater
escapes me. Once the 50 gals of hot water in the tank is gone, for
the tankless to be of any significant benefit, it's going to have to
have enough capacity to pretty much heat the incoming water up to full
temp. This means a gas fired unit of sufficient capacity. Once you
have that, what's the point to having the tank heater too? It just
defeats one of the main features of the tankless, which is no standby
loss of heat from the tank.

And forget the greywater heat exchanger, as you're never going to
recover enough heat from tepid water going down the drain to heat
incoming fresh cold water anywhere near to the point of it being
usable. Just more pie in the sky ideas, without regard to the real
world.

Well a small single faucet 200 buck unit probably wouldnt help at all


but any raise in incoming water temp will yield more hot water...

OK, incoming water is 45 deg. Outgoing is 65 deg. Want to take a
shower with that? The point is, for a flow rate sufficient to supply
additional hot water realtime to 2 bathrooms after the tank is
exhausted, you need a big tankless. Anything short of that isn;t
going to do it, and once you have that, you don't need the tank. In
fact, the tank water heater defeats one main purpose of the tankless,
which is to save energy by eliminating standby loss.






witha new hot water heater adding a tempering valve and setting btank
to max will help some

the OP should of purvhased a high BTU tank for greater recovery.

if theres space adding a second regular tank in series should fix his
problem./

frankly i HATE running out of hot water!

wrote:
wrote:

The whole point of putting a tankless in series with a tank type heater
escapes me. Once the 50 gals of hot water in the tank is gone, for
the tankless to be of any significant benefit, it's going to have to
have enough capacity to pretty much heat the incoming water up to full
temp. This means a gas fired unit of sufficient capacity. Once you
have that, what's the point to having the tank heater too? It just
defeats one of the main features of the tankless, which is no standby
loss of heat from the tank.


if your heater is in say a basement the standby losses go to help heat
your home in the winter......

so for mant the supposed savings of a tankless are a dream, espically
when you consider the initial cost of a tankless and its installation.

I doubt a small tankless will help the OP, but its his $$$

I really dont understand his concrn about low flow, a 50 gallon tank
type can provide low flow forever.

if low flow is say washing hands.

high flow is showering or laundry

wrote in message
ups.com...
I have a 50Gal hot water heater under my house serving 2 bathrooms and
four people. I am looking for a safe way to prolong the availability of
hot water when two or three people take a shower in a row. I was
thinking about putting an inline water heater before the 50gal tank
heater. I don't want to buy a big inline heater, as it's just going to
be for stretching out the hot water available during a 40 minute
period. The problem I see is the max flow through the inline unit will
be too small. Do they make inline units that will flow at arbitrary
rates, and just heat the water less when flowing fast? This would be
ideal for me. Otherwise, could I split the flow (in parallel) going
into the tank water heater: half through the inline unit, and 2) half
through some restrictor valve to even the bias?


After convincing people to take shorter showers, the first
thing to do is make sure that your showerheads are LOW flow
units. Get ones with a shut-off on it to turn the water off while
soaping up, and teach people to use it. If your shower valves
allow it, don't turn the water all the way on to shower.
If you still have a problem, turn up the water heater temp.
If you are concerned about scalding, a tempering valve on
the output would help. Next step would be to upsize the water
heater, or replace it with a faster recovery unit.
Any of these steps should be cheaper than a big enough
inline unit to do any good.

Bob

wrote:

I have a 50Gal hot water heater under my house serving 2 bathrooms and
four people. I am looking for a safe way to prolong the availability of
hot water when two or three people take a shower in a row. I was
thinking about putting an inline water heater before the 50gal tank
heater. I don't want to buy a big inline heater, as it's just going to
be for stretching out the hot water available during a 40 minute
period. The problem I see is the max flow through the inline unit will
be too small. Do they make inline units that will flow at arbitrary
rates, and just heat the water less when flowing fast? This would be
ideal for me. Otherwise, could I split the flow (in parallel) going
into the tank water heater: half through the inline unit, and 2) half
through some restrictor valve to even the bias?
If it were me I'd reverse the connection you propose, incoming cold to HW
tank, then output that to the tankless. Set the HW tank temp down very low
(start at somewhere below 90F, adjust to suit as you get experience with it)
so the Tankless has to manage a smaller temperature rise. Then you'd pretty
much have unlimited hot water.
Here's what i did. I got an old HW tank, stripped off the shell and painted
the tank flat black with rustoleum [several coats]. It sits on a small
concrete pad i made outside my garage on south side. Then I plumbed it in
series with the HW tank, the incoming cold goes to the black tank, sun
heats it a bit (its outside in the sun) and the mildly warm water feeds
into the cold inlet on the HW tank in the garage. This reduces the work
load of the water heater and lowers my bill. The outside tank has a
temperature relief as does the inside tank for safety. The inside tank is
blanket wrapped to also improve its efficiency. My next addition will be to
build a plexiglass box around the outside tank and, being up here in NW US
where winters are generally above freezing, that should extend the portion
of each year i can use it by quite a bit.
Eric

Of course its bypassed and drained in the winter but in summer it makes a
significant contribution to heating my water.

Eric wrote:
wrote:

I have a 50Gal hot water heater under my house serving 2 bathrooms and
four people. I am looking for a safe way to prolong the availability of
hot water when two or three people take a shower in a row. I was
thinking about putting an inline water heater before the 50gal tank
heater. I don't want to buy a big inline heater, as it's just going to
be for stretching out the hot water available during a 40 minute
period. The problem I see is the max flow through the inline unit will
be too small. Do they make inline units that will flow at arbitrary
rates, and just heat the water less when flowing fast? This would be
ideal for me. Otherwise, could I split the flow (in parallel) going
into the tank water heater: half through the inline unit, and 2) half
through some restrictor valve to even the bias?
If it were me I'd reverse the connection you propose, incoming cold to HW
tank, then output that to the tankless. Set the HW tank temp down very low
(start at somewhere below 90F, adjust to suit as you get experience with it)
so the Tankless has to manage a smaller temperature rise. Then you'd pretty
much have unlimited hot water.
Here's what i did. I got an old HW tank, stripped off the shell and painted
the tank flat black with rustoleum [several coats]. It sits on a small
concrete pad i made outside my garage on south side. Then I plumbed it in
series with the HW tank, the incoming cold goes to the black tank, sun
heats it a bit (its outside in the sun) and the mildly warm water feeds
into the cold inlet on the HW tank in the garage. This reduces the work
load of the water heater and lowers my bill. The outside tank has a
temperature relief as does the inside tank for safety. The inside tank is
blanket wrapped to also improve its efficiency. My next addition will be to
build a plexiglass box around the outside tank and, being up here in NW US
where winters are generally above freezing, that should extend the portion
of each year i can use it by quite a bit.
Eric

Of course its bypassed and drained in the winter but in summer it makes a
significant contribution to heating my water.

I like the reversing the order idea, but something tells me there might
be no difference. I don't want low flow shower heads, we like hot,
powerfull showers. I thought there would be some continuous mixing in a
water heater tank, everyone here talks like there isn't. I still think
adding the inline unit would get me a lot more hot shower quality water.

wrote:
cm wrote:
Go tankless.


AND HAVE TROUBLES! Low flow no hot water, power failure no hot water,
need to upgrade power or gas lines and perhaps still no be happy

SNIP

I have a tankless unit that makes it own power to start the flame, it needs
no power what so ever from external sources, there is a wheel that spins as
water passes by it producing the spark needed to start the flame. As long as
the city is still pushing water I'll have endless hot water. I bought the
Bosch Aqua Star. Great product in my opinion.

Rich

I like the reversing the order idea, but something tells me there might
be no difference. I don't want low flow shower heads, we like hot,
powerfull showers. I thought there would be some continuous mixing in a
water heater tank, everyone here talks like there isn't. I still think
adding the inline unit would get me a lot more hot shower quality water.

in line unit can add only its rated number of BTUs per hour no matter
where its located.

a small unit wouldnt help much

hot hot do you keep your tank currently?

On 23 Nov 2006 08:24:36 -0800, "
wrote:



I like the reversing the order idea, but something tells me there might
be no difference. I don't want low flow shower heads, we like hot,
powerfull showers. I thought there would be some continuous mixing in a
water heater tank, everyone here talks like there isn't. I still think
adding the inline unit would get me a lot more hot shower quality water.

in line unit can add only its rated number of BTUs per hour no matter
where its located.

a small unit wouldnt help much

hot hot do you keep your tank currently?


Any electric on-demand HWH would use an incredible about of power to
do any good. You might have to upgrade your service equipment
(breaker box and lines to the utility transformer) just to serve this
load.

Gas on-demand hot water heaters have there own expensive issues with
venting requirments and code restrictions regarding where it can be
placed. It may be just an illusion that these are cheaper when you
consider installation expenses, availability of replacement parts,
etc.

A larger capacity traditional tank HWH in a gas model is the way that
I'd go. Water heaters, in addition to size are rated by recovery time
(the time it takes to heat the tank back to usuable conditions after
all of the hot water is gone). Gas is always superior to electic in
the same volume range, and cheaper too, in most areas.

Beachcomber

wrote:


Eric wrote:
wrote:

I have a 50Gal hot water heater under my house serving 2 bathrooms and
four people. I am looking for a safe way to prolong the availability of
hot water when two or three people take a shower in a row. I was
thinking about putting an inline water heater before the 50gal tank
heater. I don't want to buy a big inline heater, as it's just going to
be for stretching out the hot water available during a 40 minute
period. The problem I see is the max flow through the inline unit will
be too small. Do they make inline units that will flow at arbitrary
rates, and just heat the water less when flowing fast? This would be
ideal for me. Otherwise, could I split the flow (in parallel) going
into the tank water heater: half through the inline unit, and 2) half
through some restrictor valve to even the bias?
If it were me I'd reverse the connection you propose, incoming cold to HW
tank, then output that to the tankless. Set the HW tank temp down very
low (start at somewhere below 90F, adjust to suit as you get experience
with it) so the Tankless has to manage a smaller temperature rise. Then
you'd pretty much have unlimited hot water.
Here's what i did. I got an old HW tank, stripped off the shell and
painted
the tank flat black with rustoleum [several coats]. It sits on a small
concrete pad i made outside my garage on south side. Then I plumbed it in
series with the HW tank, the incoming cold goes to the black tank, sun
heats it a bit (its outside in the sun) and the mildly warm water feeds
into the cold inlet on the HW tank in the garage. This reduces the work
load of the water heater and lowers my bill. The outside tank has a
temperature relief as does the inside tank for safety. The inside tank is
blanket wrapped to also improve its efficiency. My next addition will be
to build a plexiglass box around the outside tank and, being up here in
NW US where winters are generally above freezing, that should extend the
portion of each year i can use it by quite a bit.
Eric

Of course its bypassed and drained in the winter but in summer it makes a
significant contribution to heating my water.

I like the reversing the order idea, but something tells me there might
be no difference. I don't want low flow shower heads, we like hot,
powerfull showers. I thought there would be some continuous mixing in a
water heater tank, everyone here talks like there isn't. I still think
adding the inline unit would get me a lot more hot shower quality water.

Forget those low flow shower heads, life is too short to live like a refugee
The trick is to find a way to be able to afford these benefits.
Doing what i said above with the tankless water heater "After" the Tank type
heater will give you way more HW at a single period of time than you should
need or want. I Promise. The Tankless can supply water just about
continuously at say 3GPM/60F temp rise so if your ground water is 55F then
the tankless alone can supply 115 degree water forever. But thats at max
capabilities and you never want to run at that level, so if you insert a
standard water heater BEFORE the tankless and supply the tankless with 80
or even 70 degree water then the tankless isnt maxed out and can supply
that 115 degree water at much higher GPM, ie the tankless is only working
at some percent capacity and can handle fluctuations in demand easily. When
its operating at max capacity any fluctuation in demand will cause a
temperature change.
There is continuous mixing of water in a HW tank, cold comes in the top,
down the dip tube to the bottom and into the surrounding HW. HW goes out
the top of the tank, it cant help but mix. But the water in the tank is
much hotter near the tanks top than it is at the bottom. Thats why a 50
gallon HW tank can produce a first hour rating of 79 gallons, you dont have
just 50 gallons of HW, you have 50 gallons of "too hot" water so you
effectively can get more gallons of "just right" hot water out of it.
Plus the tanks heater (gas or electric) comes on when the temp drops to the
setpoint and starts adding heat to the contents - these 2 things work
together to give you that 79 gallons of HW from the 50 gallon tank.
Eric