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Thread: On demand hot water recirculation pump

  1. #1
    DIY Senior Member Homeownerinburb's Avatar
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    Default On demand hot water recirculation pump

    Hey,

    I am looking for a recirculation pump that only works on demand.

    I want to mount it under the kitchen sink (the furthest distant from the water heater) where I have power. And I want for it to only run if I tell it to. I want for it to push the cooled hot water into the cold water pipe until it raises the temp at the hot water faucet to a reasonable level.

    I also need to be able to cause it to run from a point in one of the bathrooms.

    I have been researching a bit, and thus far pretty much everything I find has at least one page of people who have used one or another and found it to be worthless.

    Can anyone recommend a particular brand/model?

  2. #2
    DIY Member SAS's Avatar
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    I have the Metlund D'Mand system. I took a quick look and I believe it is also sold as the Taco D'Mand System. Here's the website where I bought it. http://www.hvacquick.com/howtos/howto.php
    I installed it in 2006 and have been very happy with it. It's installed under the vanity in the master bedroom bathroom (farthest point from the hot water heater). I have a wired button on the wall (with a pilot light I added to tell when it's finished running - although you could probably just listen for the pump). I also have two wireless buttons in other bathrooms. It takes a minute or two to warm up the water, and it does mean that your cold water tap will have slightly warm water after the pump runs. My 93 year old father in law loves it. When he gets up in the middle of the night he hits the button before using the toilet and when he washes his hands he doesn't have to do it with ice cold water (we're in CT with our own well, so the cold water is very cold). Except for changing the batteries on the wireless buttons, it has been maintenance free for nearly 8 years.

    Edit: It looks as if the Metlund S70, which is what I have, is no longer available.
    Last edited by SAS; 02-04-2014 at 06:37 AM.

  3. #3
    In the Trades Gary Swart's Avatar
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    You should consider a system with a pump. These do require a return line which might be a problem for you, but these will give you true instant hot water. They can be on a timer, but I run mine 24/7.

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    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by Homeownerinburb View Post
    Can anyone recommend a particular brand/model?
    I have no first hand experience with one so cannot make a specific recommendation, but have found many on the internet with a variety of features, including timers, motion sensors, and push buttons.

    If you want manual activation from two places, then a push button at each should be possible but of course would require running wires.

    Why not just go with a Grundfos Comfort system and use the timer? Alternately, you could plug it into an outlet that is controlled by a wireless motion sensor and/or wireless key fob. I have a Carlon Lamson and Sessions motion sensor that would do the trick.
    http://ca.grundfos.com/content/dam/G...02_UP10-16.pdf
    http://www.lamson-home.com/ProductSu.../HS3605_im.pdf

  5. #5
    DIY Senior Member Homeownerinburb's Avatar
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    Possibly I did not define my purposes adequately.

    I am after the maximum conservation effect.

    I'm tired of dumping water to get hot water.

    And I don't need a pump to move water around when it is not needed.

    One that just makes sure that you always have hot water at all taps at all times wastes both gas and electricity.

    Plus, these pumps don't last forever. The more they work, the less they last.

    I want a pump to move the cold water back to the heater when anyone needs to wash the dishes or take a shower.

    I don't need the system to do anything else at any other time.

  6. #6
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by Homeownerinburb View Post
    And I don't need a pump to move water around when it is not needed.
    Most of the POU units I researched shut themselves off once the water is hot and don't continuously recirculate. If they did, you would get hot water from the cold tap but all you get is tepid water. If you get the type with motion sensor or push button, they don't run at all until someone enters the room/pushes the button.

    Of course the central type such as the Grundfos are different than the POU types but then that is why they have a timer.

  7. #7
    In the Trades Gary Swart's Avatar
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    I use a Laing, and I think the Grundfos is fairly similar. The hot water circulates through the regular hot water line and back to the tank through the return line. Since I run my system 24/7, there is always instant hot water when I want it. No purging cold water. Now, the same system could have a timer on the pump, and would provide instant hot only when the pump was running. Other times you would have to purge the cold. I, and most folks using a return line insulate both the hot water supply line and the return line, but I can't verify how much actual savings this amounts to. These pumps do not draw a lot of electricity, so I doubt you would notice much if any change in your power bill. As I said in my previous post, installing a return line could be a problem or not depending on your home construction. My system has been operating for about 12 years, non stop with zero problems. I imagine one day the pump will go out, but it will be easy to replace. So. that's my biased opinion.

  8. #8
    DIY Member SAS's Avatar
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    Quote Originally Posted by Homeownerinburb View Post
    Possibly I did not define my purposes adequately.

    I am after the maximum conservation effect.

    I'm tired of dumping water to get hot water.

    And I don't need a pump to move water around when it is not needed.

    One that just makes sure that you always have hot water at all taps at all times wastes both gas and electricity.

    Plus, these pumps don't last forever. The more they work, the less they last.

    I want a pump to move the cold water back to the heater when anyone needs to wash the dishes or take a shower.

    I don't need the system to do anything else at any other time.
    Here's the one I have. It is pricey, but it does exactly what you want and has proven very reliable.

    Metlund D'MAND Sts-70T Hot Water Circulation System

    In my new house I have a pump that circulates whenever the hot water in the pipes gets too cool, and while it is more convenient than the on demand unit, if I were in your shoes I would still buy the Metlund unit. The exception I would make is if your house is empty all day and/or no one gets up in the middle of the night. In that case the circulating pump and timer would make more sense.
    Last edited by Terry; 02-04-2014 at 10:59 PM.

  9. #9
    DIY Senior Member Homeownerinburb's Avatar
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    Quote Originally Posted by Gary Swart View Post
    I use a Laing, and I think the Grundfos is fairly similar. The hot water circulates through the regular hot water line and back to the tank through the return line. Since I run my system 24/7, there is always instant hot water when I want it.
    Please see my comment up the page.

    I don't want a pump that pumps to maintain the heat.

    That is grossly wasteful of energy.

  10. #10
    Moderator & Master Plumber hj's Avatar
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    quote; I don't want a pump that pumps to maintain the heat.

    ANY of the systems will do what you desire, IF you plug them in to a wireless switched outlet, such as the X-10 unit that you operate with a remote control from ANYWHERE in the building
    Licensed residential and commercial plumber

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    The Redy-Temp unit does what you want to do and would be an easy install since you already have power. http://redytemp.com/ Mine is about 9-years old. I have it on a timer so it only runs when I'm up, but it is easy to patch in whatever control (wireless, always on, timer) you choose. It has a user adjustable aquastat so you can set your desired shutoff point. I have mine set to warm (the shower is closer to the supply so it's hot faster) and in the winter, it tends to run maybe 60-seconds every 15-minutes or so. That would depend on where and how your pipes run and how well they are insulated. The basic install should take literally, less than 10-minutes, depending on the model you choose.

    If your pipes are well insulated, the pump size is quite small, so it really doesn't draw much even on those models that run continuously.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  12. #12
    DIY Senior Member Homeownerinburb's Avatar
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    Quote Originally Posted by jadnashua View Post
    The Redy-Temp unit does what you want to do and would be an easy install since you already have power. http://redytemp.com/ Mine is about 9-years old. I have it on a timer so it only runs when I'm up, but it is easy to patch in whatever control (wireless, always on, timer) you choose. It has a user adjustable aquastat so you can set your desired shutoff point. I have mine set to warm (the shower is closer to the supply so it's hot faster) and in the winter, it tends to run maybe 60-seconds every 15-minutes or so. That would depend on where and how your pipes run and how well they are insulated. The basic install should take literally, less than 10-minutes, depending on the model you choose.

    If your pipes are well insulated, the pump size is quite small, so it really doesn't draw much even on those models that run continuously.
    Jim,

    It is not so much the electricity to drive the dratted thing that is wasteful, but to be constantly heating water when there is no demand for it.

    I want to only cause the pump to run when someone makes the deliberate effort to turn the pump on, with the aquastat shutting it off until signaled again.

    These things are pricey. But I'd admit that quality comes at a price.

  13. #13
    Retired Defense Industry Engineer jadnashua's Avatar
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    It somewhat depends on how often you use water and how much you need to run before you get the hot or warm where you need it. Keep in mind, also, that at least during part of the year, and heat given off from the water pipes is also helping to heat the space as well. If it takes 90-seconds to get hot, and you dump 3-4 gallons of water down the drain multiple times during the day, keep in mind you're also putting warm water back into the WH from the recirculation verses potentially MUCH colder water than if you dump it down the drain. Also, by recirculating it, you're not dumping it down the drain to go to the sewer, which may have it's own costs. At least one test I saw said that with a timer, the actual energy and sewer charges, a recirculation system is actually less expensive.

    BTW, pretty much all of the systems can be setup the way you want. But, having it there when you want it, especially if you have guests, it's nice when just on a timer rather than potentially having to wait a couple of minutes for it to be warm or hot there. You can have it both ways, too...have it on a timer during the day, and on-demand, momentary at night.
    Last edited by jadnashua; 02-05-2014 at 09:26 PM.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    In the Trades Gary Swart's Avatar
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    Hope you can find what you think you want. I will leave you with this last comment. You are way over thinking that there is a huge waste of energy with a recirculation pump. The water recirculates back into the tank and has lost very little heat. Even with mine operating 24/7 I can not determine there is any significant expense. With a timer, there would be even less, but the trade off would be having to purge the cold water if I wanted hot water during the off period.

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