Water heater flow question

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?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

snipped-for-privacy@gmail.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Takagi has a controller to allow you to so this with their T-M1s:
http://www.tanklesswaterheatersdirect.com/shop/tanklesswaterheaters/takagi/takagitm1main.asp
Michael Thomas Paragon Property Services Home Inspections http://www.paragoninspects.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Michael Thomas, Paragon Property Services, http://www.paragoninspects.com "

http://www.tanklesswaterheatersdirect.com/shop/tanklesswaterheaters/takagi/takagitm1main.asp
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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

A simple fix would be to stop yanking your monkey in the shower. Nobody needs to shower that long. Bubba
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The heater's output is dependent in part on the inlet water temp:
http://lib.store.yahoo.net/lib/lowenergysystems/tk1-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-inspection-tankless-water-heater-installation-problems-faq.html
Michael Thomas Paragon Property Services Home Inspections http://www.paragoninspects.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bubba wrote:

It's the same deal as with assault weapons and most SUVs.
NEED is not the criteria; WANT is the deciding factor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.