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Thread: Problem with tankless + recirc pump. This is a tricky one

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  1. #1

    Default Problem with tankless + recirc pump. This is a tricky one

    I'll do my best to explain my predicament. I had a house built and installed Takagi TM-1 on demand water heater. It was located at the far end of the house away from the gas meter. We installed a Metlund "on demand" pump right off the water heater which was directly attached to a recirc loop. The pump is activated by buttons in the house and the recirc worked great. The problem was that the plumbers did not read the specs carefully and the water heater required more gas than could really reach the water heater so when the home gas heater was on the water heater would shut off and we would get stuck in cold showers.

    To resolve that problem we moved the tankless to the other end of the house right next to the gas meter. The plumbers tapped into existing lines for hot and cold water, but there was no practical way to tie directly into the recirc line at the water heater itself. We left the pump at the opposite end of the house hoping it could "pull" the water through the recirc. The problem is now when we hit a button to activate the pump the pump kicks in and runs for three minutes before shutting off (built in max run time). I have verified that hot water never gets pulled through the recirc loop. It seems that the existing water in the lines is just following the path of least resistance and going in a circle. There is nothing forcing it to pull down the line that reaches the hot water heater.

    Is there any way to make this work without moving the water heater or the pump and without tearing out more drywall to find the loop at that end of the house? Moving the water heater is not an option. It has to be close to the meter to solve the original problem. We could move the pump easily enough, but is there a way to take advantage of the recirc loop which we went to the trouble of putting in? I'd rather do that than recirc through the cold water line if possible. I imagine there may be more than one way to resolve this, but I'm just the homeowner. Unfortunately I seem to have a better grasp of the situation than my plumber who told me this setup should work.

  2. #2
    Master Plumber master plumber mark's Avatar
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    Talking thats a great story

    I dont know what you can do to solve this problem

    the tankless water heaters are nothing but trouble...

    and it looks like you plumber is getting his education in your home

    did your plumber mention that most of these units
    need to be purged every 2 months even when they are working
    correctly, .......

    I have heard it before....

    have you considered just putting in a a 50 gallon gas heater
    and saveing yourself a ton of greif???

    do you still owe the plumber any money???
    Last edited by master plumber mark; 03-29-2006 at 11:55 PM.

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default pump

    A pump always moves water "in a circle". The problem is that the heater has to be part of that circle. Unless you can find a way to incorporate the heater into the pumps's circulation loop, it is not going to work. I would think it would have been cheaper to run a gas line to the heater than to move it, but your house may not have been amenable to doing that.

  4. #4
    In the Trades Bob NH's Avatar
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    Default

    Putting an "on-demand" circulator pump together with a demand water heater in a system that doesn't work properly could probably be considered negligence subject to recovery from the "professional" who designed and installed it. I can't imagine any circumstance where it would make sense.

    It sounds like someone designed the system with pipe cutter and torch instead of with pencil and paper.

    I would want to see a complete diagram of the existing system before trying to fix it. It may require a new system designed around what you can salvage of the pipes that are in place.

  5. #5
    Plumber jimbo's Avatar
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    Default

    First, if the sales person at the plumbing store or box store did not discuss with you basic issues like gas requirements, you need to have a discussion with the manager. Then, if your plumber did not even open the insall intructions to page one, you should be having a discussion with his boss. I hope he didn't charge you to move the unit.

  6. #6

    Default Further information

    Thanks for the responses so far. There were a couple questions in the responses so I will clarify a few things ...

    I can always put in a 50 gallon tank in the original location (nothing bigger than that will fit), but then we will almost certainly run out of hot water at times since this is a large house with 5 bathrooms and 6 people. The tankless unit is spec'd at 9.6 GPM which has always been enough for a couple showers plus washing machine or whatever so far. We've been satisfied with that aspect of it.

    I feel I should do a better job describing the recirc loop and heater pump setup. The home is on a hillside and has a half walkout basement on the downhill side. The recirc loop is all in the ceiling upstairs. The pump (and original location of hot water heater) is at far end of house on uphill side. The water heater is now at far end of house on downhill side at ground level. So the plumber tapped into the line that ran from recirc loop upstairs to feed the two bathrooms downstairs. Likewise with the cold water line. So the entire loop is in the ceiling upstairs and the heater is mounted on the outside of the house at ground level downstairs.

    Running a gas line was not cost effective because it would have been around 150' of (probably) 2" pipe and there is no easy way to conceal it without ripping into the walls. Moving the heater was a simple matter of disconnecting four bolts and reinstalling it on the outside of the home and tapping into existing lines. That's why we moved the water heater.

    I get a sense of sympathy from everyone which is nice, but I'd like to know if anyone has any suggestions. I realize without knowing the pipe layout you can only go so far, but here is what I see as viable options to solve my problem. I'd like a "sanity check" if anyone has the time...

    Option 1: Disconnect the pump from the recirc loop and install it under the sink in the bathroom at the far end of the house. This would utilize the cold water line for the return. This is how the Metlund pump system is typically used so I know it should work. The downside is that I don't use the recirc that is already there. I'm not sure if there are any negatives from using the cold water as the return. Another downside is that the pump can be pretty loud when its going. Another downside is I think this might be a negative when I go to sell the home (its a high-end home and would seem strange to not have a dedicated recird line). I may be selling the home within the year

    Option 2: Move the pump to the other side of the house so it pulls off the water heater. This is where I have big gaps because of my lack of plumbing knowledge. If the pump activates the water heater and draws hot water directly out of the heater and pushes it up the pipe, it seems that it would eventually hit the recirc line (although I fear it might have to fill every side channel to each faucet en route) and then it should loop through the recirc, but I'm not sure what to do for the return path. I don't understand how the recirc loops in general. After the water completes the loop where does it go? Do you need it to drain somewhere? Anyway, is it possible to move the pump to the heater without having the recirc return directly tied into the pump?

    Option 3: As a variant to Option 2 ... We have used one existing hot water line that ran from the basement up into the recirc loop which is currently connected to the heater. If we find another existing hot water line that runs into the basement could we tie that to the return side of the pump and basically create a new path for the recirc loop?

    Option 4: Lets just say I spring for a new 50 gallon water heater and put it in the original location (of course I would really rather not incur the cost). Is there any way to use that in tandem with the tankless so the tankless only kicks in when the supply in the 50 gallon tank is depleted? If this is possible at all does it matter where the tankless heater is installed (current location vs original location)?


    $$$ Dilemma: I apologize for the length of this post. Anyone who has even read this far is my hero. I'd like to ask one more question. The sense I got from the original responses was that the plumber should bear most of the responsibility for this problem. Of course I had considered that, but did not know how much to pin on him. When we built the house I did it as an owner-builder so acted as the general contractor. I did provide the specs to the plumber (who is a licensed contractor), but I chose the location of the heater and pump. The original configuration would have worked great if there was sufficiently sized gas line running to that end of the house. He should have seen it in the specs (its clearly called out there), but perhaps I should have pointed it out specifically? I'm not sure on that one. For this more recent SNAFU I have no problem pinning it on the plumber. I had him come out and look at the situation to make sure it would work with the on demand pump before moving anything. He told me it would work, and obviously it does not. I have not paid for moving the water heater or any work after the original install, but I had agreed to pay some of it originally. How much of the bill should I be responsible for?

    Thanks so much for everyone's responses. What a great board this is!

  7. #7
    In the Trades Bob NH's Avatar
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    Default If I Had What You Have . . .

    If I couldn't get my money back from the plumber for a modification that doesn't work:

    1. I would leave the instant hot water heater where it is.

    2. Forget the circulator. Take it out of the system.

    3. Put an electric Point of Use heater at the end of the line; something like the Ariston GL4, but at least 5 times the volume of the water in your hot water pipe between the Demand Heater and the POU heater.

    The system would work as follows:
    When you demand hot water at the end of the line, the POU heater provides it instantly. The Demand Water Heater will supply hot water to the POU heater, which will get cooler but still be hot until the hot water arrives from the demand heater.

    Maybe your plumber will pay for the POU heater and the cost of installing it. They are not expensive and need only a 115 Volt circuit.

  8. #8
    Master Plumber master plumber mark's Avatar
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    Talking a 5 bathroom home--cant work..

    honestly , I doubt itwill ever make you happy with

    5 bathrooms to feed.....and how many people???


    The plumber should have cried FOUL when you said you wanted one...
    and read the instructions.....

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

    Basically , once the wife has had her fill with all the

    tweaking and tinkering , eventually she is going to take her last pisswater

    shower.

    Then YOU will have something like

    "the mutiney on the Bounty" happen with your family........

    they will threaten to go to a hotel for a hot shower and force

    you to bend to the pressure.....

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

    Just install a 75 gallon heater....that will certanly do the job.....

    I think a brad white 75 gallon is not that big,, 22 inches round

    and even if you have to take out some dryallll to make it fit into the space

    at least the problem is solved and you can move on


    closure is good with your plumber too....


    THEN that recurlulation line will work great>>>>
    ----------------------------------------------------------------------

    I honestly doubt that you can even get a good enough
    FLOW RATE through that tankless unit for people to take two showers at the same time in this house....it simply aint gonna happen

    even if you changed over your whole house to a 2lb wardflex gas system
    you would probably have to run at least 3/4 or maybe a one inch line from the mainfold

    but honestly its just a matter of time before it fails you anyway...


    so I suggest you just bite the bullett --and get a 75 gal

    Just look at this as a learning experience and try to mend fences with
    your plumber......
    I am sure he would like to tear out that piece of
    junk too and get the job completed the right way.
    Last edited by master plumber mark; 03-31-2006 at 05:03 AM.

  9. #9
    Moderator & Master Plumber hj's Avatar
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    Default heater

    We cannot really address options #2, 3, and 4, because they require more knowledge about your system than we have. With option #1, you would have to have a device to shut off the flow into the cold water pipe when the hot water arrives or it will fill with hot water. If we were there, we might be able to say, "Boy, this is simple. All you do is ................................".

  10. #10

    Smile thanks everyone

    Thanks everyone for your responses. My plumber is coming back out to take a look at our options. Hopefully between his knowledge of plumbing and my common sense we can figure something out. Your responses helped let me know some of my limitations and gave me a better feeling of where the responsibility should lie.

    One last comment for master plumber mark. I understand that you don't like tankless heaters. That is evident from your previous posts. But I have no complaints with this heater. The heater itself has worked great. The only problems have been the setup. We have been able to run two showers plus body spray and a dishwasher at the same time with no noticable impact to water flow or temperature. I'm sure it helps that I'm in Tucson, AZ and the ground water coming in is probably much warmer than where you are. This is the highest GPM unit I could find because I knew we had a big house with high demands. The way I see it we could have 20 bathrooms, but as long as we are only doing 2-3 showers (or other sustained water use) at the same time it doesn't matter. I got it so we could theoretically take 10 showers in a row for as long as you want and not have it run out. In short my tankless has been great for my needs. I understand that it may not be right for everyone though

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