Hi all:

I've got a tankless water heater which I love - as I tend to take
extended showers sometimes and I love not worrying about when it will
run out. I recently have upgraded my shower, however, to include
multiple shower heads/body sprays, and now it appears the tankless
doesn't have the GPM output to support the flow of these devices (the
water is pretty much just a trickle when they are all on). I know
there are at least two choices on how to solve this, neither of which
I am particularly enamored with.

1) Add one or two more tankless water heaters in parallel in a
manifold - this is extremely expensive
2) Replace the tankless with a large (e.g., 75 gallon) traditional
water heater - I don't like this one since I may go back to running
out of hot water, although it would clearly provide the flow I need.

What I am wondering is about a third option - putting a 75 gallon
water heater in series with the tankless - the 75 gallon being located
after the tankless in the run. While I understand that once the 75
gallon is out of hot water the flow output would definitely be as low
as the tankless puts out, what I don't know is what happens before
that. Say the tankless puts out 5GPM while the pipes themselves (and
the tank) can put out 50GPM. If I use this set up, does that mean I
can get up to 50GPM until the tank runs out, and then the system will
only be able to put out 5GPM, or will the rate limiting of the
tankless limit the whole system throughout and the tank will only put
out 5GPM even when it is full of hot water?

On 13 déc, 08:21, none wrote:
Hi all:

I've got a tankless water heater which I love - as I tend to take
extended showers sometimes and I love not worrying about when it will
run out. I recently have upgraded my shower, however, to include
multiple shower heads/body sprays, and now it appears the tankless
doesn't have the GPM output to support the flow of these devices (the
water is pretty much just a trickle when they are all on). I know
there are at least two choices on how to solve this, neither of which
I am particularly enamored with.

1) Add one or two more tankless water heaters in parallel in a
manifold - this is extremely expensive
2) Replace the tankless with a large (e.g., 75 gallon) traditional
water heater - I don't like this one since I may go back to running
out of hot water, although it would clearly provide the flow I need.

What I am wondering is about a third option - putting a 75 gallon
water heater in series with the tankless - the 75 gallon being located
after the tankless in the run. While I understand that once the 75
gallon is out of hot water the flow output would definitely be as low
as the tankless puts out, what I don't know is what happens before
that. Say the tankless puts out 5GPM while the pipes themselves (and
the tank) can put out 50GPM. If I use this set up, does that mean I
can get up to 50GPM until the tank runs out, and then the system will
only be able to put out 5GPM, or will the rate limiting of the
tankless limit the whole system throughout and the tank will only put
out 5GPM even when it is full of hot water?

wrote in message
...
On 13 déc, 08:21, none wrote:
Hi all:

I've got a tankless water heater which I love - as I tend to take
extended showers sometimes and I love not worrying about when it will
run out. I recently have upgraded my shower, however, to include
multiple shower heads/body sprays, and now it appears the tankless
doesn't have the GPM output to support the flow of these devices (the
water is pretty much just a trickle when they are all on). I know
there are at least two choices on how to solve this, neither of which
I am particularly enamored with.

1) Add one or two more tankless water heaters in parallel in a
manifold - this is extremely expensive
2) Replace the tankless with a large (e.g., 75 gallon) traditional
water heater - I don't like this one since I may go back to running
out of hot water, although it would clearly provide the flow I need.

What I am wondering is about a third option - putting a 75 gallon
water heater in series with the tankless - the 75 gallon being located
after the tankless in the run. While I understand that once the 75
gallon is out of hot water the flow output would definitely be as low
as the tankless puts out, what I don't know is what happens before
that. Say the tankless puts out 5GPM while the pipes themselves (and
the tank) can put out 50GPM. If I use this set up, does that mean I
can get up to 50GPM until the tank runs out, and then the system will
only be able to put out 5GPM, or will the rate limiting of the
tankless limit the whole system throughout and the tank will only put
out 5GPM even when it is full of hot water?

No, you cannot put one in series to corect a flow issue. If would still be
restricting the flow as the water still needs to flow thru tankless , thus
still the 5GPM, you can't get more out of a tank than you are putting in to
it. Parralel devices add, series devices is the flow of the lowest device.
Putting 2 in parralel would give you a 10GPM flow at the shower, 3 15GPM, 4
20GPM etc

------water line
50GPM-----Tankless------5GPM-------Tank-------5GPM-------shower
------water line 50GPM-----Tankless------5GPM-------shower
------water line 50GPM-------Tank-------50GPM-------shower

The heater's output is dependent in part on the inlet water temp:

http://lib.store.yahoo.net/lib/lowen...temp-chart.jpg

so you live in a cold climate and and your water supply is at 45-50F
or less (mine goes as low as 38F) one possibility is a passive
"tempering tank" located in a heated area and plumbed ahead of the
heater - I've read about this, but not seen it done,

I elected to prevent this problem by installing a Takagi T-M1 at my
home (T-M1), I also have Takagi T-KD20s at my office and at 3 of our
rentals. They work well if properly installed, but we encountered a
LOT of issues when installing them.

I have a web page up where I discuss some of the problems we have
encountered, and how to avoid them. It also has a link to an OA Smith
white paper on calculating the payback of tankless heaters:

http://paragoninspects.com/home-insp...blems-faq.html

Michael Thomas
Paragon Property Services Home Inspections
http://www.paragoninspects.com

No, you cannot put one in series to correct a flow issue. If would still be
restricting the flow as the water still needs to flow thru tankless , thus
still the 5GPM, you can't get more out of a tank than you are putting in to
it. Parallel devices add, series devices is the flow of the lowest device.
Putting 2 in parallel would give you a 10GPM flow at the shower, 3 15GPM, 4
20GPM etc

Takagi has a controller to allow you to so this with their T-M1s:

http://www.tanklesswaterheatersdirec...agitm1main.asp

Michael Thomas
Paragon Property Services Home Inspections
http://www.paragoninspects.com

Bubba wrote:

A simple fix would be to stop yanking your monkey in the shower.
Nobody needs to shower that long.
Bubba

It's the same deal as with assault weapons and most SUVs.

NEED is not the criteria; WANT is the deciding factor.

"Michael Thomas, Paragon Property Services, http://www.paragoninspects.com"
wrote in message
...
No, you cannot put one in series to correct a flow issue. If would still
be
restricting the flow as the water still needs to flow thru tankless ,
thus
still the 5GPM, you can't get more out of a tank than you are putting in
to
it. Parallel devices add, series devices is the flow of the lowest
device.
Putting 2 in parallel would give you a 10GPM flow at the shower, 3 15GPM,
4
20GPM etc

Takagi has a controller to allow you to so this with their T-M1s:

http://www.tanklesswaterheatersdirec...agitm1main.asp

Michael Thomas
Paragon Property Services Home Inspections
http://www.paragoninspects.com



They are placing the devices in parralel with eachother, nothing special,
the OP could do that with "his brand" Their "controller" opens and closes
solenoids as needed based on flow requirements.