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  1. #1
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    Default Water heater circulation pumps

    I had a weird thing happen at todays inspection. Place was high end home, new construction, vacant. The water heater has circulation pump, it was unplugged when I arrived. I did not plug it in at first, I could get hot water at one fixture right away. However it took about 20+ minutes before I got hot water in kitchen, still could not get hot water at fixtures that were furthest away from water heater. After I plugged in the circulation pump and waited for 15-20 minutes, I could then get hot water at all fixtures.

    I have never had a situation where I could not get hot water due the circulation pump not being plugged in. Wondering if there's a problem of if this is just how this particular system works?

    Inspection Referral

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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Trent Tarter View Post
    I had a weird thing happen at todays inspection. Place was high end home, new construction, vacant. The water heater has circulation pump, it was unplugged when I arrived. I did not plug it in at first, I could get hot water at one fixture right away. However it took about 20+ minutes before I got hot water in kitchen, still could not get hot water at fixtures that were furthest away from water heater. After I plugged in the circulation pump and waited for 15-20 minutes, I could then get hot water at all fixtures.

    I have never had a situation where I could not get hot water due the circulation pump not being plugged in. Wondering if there's a problem of if this is just how this particular system works?
    Missing or defective one way valve on the recirculating line

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  3. #3
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Trent Tarter View Post
    ... still could not get hot water at fixtures that were furthest away from water heater. After I plugged in the circulation pump and waited for 15-20 minutes, I could then get hot water at all fixtures.

    I have never had a situation where I could not get hot water due the circulation pump not being plugged in. Wondering if there's a problem of if this is just how this particular system works?
    Trent,

    You gave up too soon ... ... that's why the circulation pump was installed.

    You would have gotten hot water to those farthest fixtures if you had waited l-o-n-g e-n-o-u-g-h, but by then your client would have given up and called a plumber, who would have told your client that the home inspector should have caught that, who would then have called you ...

    All the circulation pump did was be patient and just keep pushing hot water through the hot water piping, after heating the copper piping up (if copper) the hot water finally got to the other end, the hot water piping for circulation pumps should be insulated (not sure if it is required where you are, but they still 'should' be insulated to keep the cost of heating the water down, many energy codes require insulation on those re-circulation lines.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  4. #4
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    Default Re: Water heater circulation pumps

    However it took about 20+ minutes before I got hot water in kitchen, still could not get hot water at fixtures that were furthest away from water heater.
    I agree, there is likely a defective check valve letting cold water bleed through when the pump is off. 20+ minutes should be long enough in any single family system.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  5. #5
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Jerry Peck View Post
    Trent,

    You gave up too soon ... ... that's why the circulation pump was installed.

    You would have gotten hot water to those farthest fixtures if you had waited l-o-n-g e-n-o-u-g-h, but by then your client would have given up and called a plumber, who would have told your client that the home inspector should have caught that, who would then have called you ...

    All the circulation pump did was be patient and just keep pushing hot water through the hot water piping, after heating the copper piping up (if copper) the hot water finally got to the other end, the hot water piping for circulation pumps should be insulated (not sure if it is required where you are, but they still 'should' be insulated to keep the cost of heating the water down, many energy codes require insulation on those re-circulation lines.
    Jerry the supply pipe is PEX and is insulated in crawlspace, this is a single story 3000 sq ft home, water heater is not that far from the furthest fixture. What I don't understand is why I could not get hot water after running water from over 20 minutes to a fixture (when circulation pump was off). Rick stated that there may be a missing or defective one way valve on the recirculating line.


  6. #6
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Trent Tarter View Post
    I had a weird thing happen at todays inspection. Place was high end home, new construction, vacant. The water heater has circulation pump, it was unplugged when I arrived. I did not plug it in at first, ...
    Quote Originally Posted by Jim Luttrall View Post
    I agree, there is likely a defective check valve letting cold water bleed through when the pump is off. 20+ minutes should be long enough in any single family system.
    No need for a check valve, the water heater should have a heat trap installed at its outlet and at its inlet, been standard equipment down here for decades.

    The system had not been containing hot water throughout the system - it was a high end home (indicating to me that it was rather large in sq ft) - both of those would lead to taking quite a while for hot water to get to a far away fixture. Add to that the if the piping is not insulated, running hot water a long distance will take a lot just to heat the piping, and then to keep it heated to continue getting hot water through the system. Copper systems are worse about that than CPVC or PEX as the copper dissipates the heat pretty quickly compared to the others.

    Pleases explain the need for a check valve and where it would be installed which would keep that from happening (I am presuming that the water heater came with heat traps for inlet and outlet, although heat traps are not necessary if the cold supply to the water heater and the hot from the water heater both turn down, that stops hot water flow by gravity as the hot water rises to the top of the piping traps and stops where the piping turns back down at least 6" before going out horizontally (but the installation of the heat traps solves the need to even those heat traps).

    Do water heaters in your area *not* come with heat trap fittings? They are steel looking nipples which have a groove around them near the middle, one is for the cold inlet and one is for the hot outlet.

    Jerry Peck, Construction / Litigation Consultant
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  7. #7
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    Default Re: Water heater circulation pumps

    I don't know much about recirculating pumps, but..
    several years ago a friend of mine installed one in his home. After he installed it seamed like he had the same problem. He asked me if I knew what was wrong, but I did not know. Later he told me he had to install a check valve and that fixed it.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  8. #8
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Rick Cantrell View Post
    Later he told me he had to install a check valve and that fixed it.
    But where, for what purpose? That is what I am inquiring about.

    About the only reason I can see to have to install a check valve is if there are no heat trap fittings/heat traps installed at the water heater.

    For single story structures where the water comes up from the floor to the water heater then goes down into the floor from the water, the water heater and the piping serve as a heat trap.

    For two story structures where the water come up the floor to the water heater, that serves as the cold-side heat trap; where the water goes up from the water heater, either a heat trap or heat trap fitting needs to be installed (all water heaters brought into Florida come with heat trap fittings, one for the inlet and one for the outlet) - without a heat trap I can see needing a check valve to stop the gravity-fed hot water circulation generated by the hot water itself.

    A 'heat trap' at a water heater is typically just a 6" piece of pipe going vertically up, an elbow, a 6" piece of pipe going horizontally, another elbow, and at least a 6" piece of pipe going vertically down - that 'traps the heat' and stops loss due to gravity circulation of the hot water.

    A 'heat trap fitting' is a fitting supplied with water heater, and available on their own if not supplied with the water heater, which is installed in the cold inlet fitting and the hot outlet fitting - the cold and hot are different so each must be in its correct fitting and installed with the arrow matching the direction of water flow ... install them backwards or install the inlet and outlet in the wrong fittings and they won't work to trap the heat from flowing by gravity from/to the water heater through the piping system.

    Heat Trap Fitting - Vertical or Horizontal Style | Bradford White Water Heaters. Built to be the best.

    http://www.americanwaterheater.com/s...ns/6500253.pdf

    Elster Perfection - Heat Trap Fittings

    Camco 3/4 in. x 2-1/2 in. Metal and Plastic Heat Trap Dielectric Nipples (2-Pack)-15132 at The Home Depot

    Last edited by Jerry Peck; 12-28-2013 at 06:33 PM. Reason: added links for heat trap fittings
    Jerry Peck, Construction / Litigation Consultant
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  9. #9
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Jim Luttrall View Post
    I agree, there is likely a defective check valve letting cold water bleed through when the pump is off. 20+ minutes should be long enough in any single family system.
    I agree Jim, there must be some type of defective valve in the system.


  10. #10
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Jerry Peck View Post
    But where, for what purpose? That is what I am inquiring about.

    About the only reason I can see to have to install a check valve is if there are no heat trap fittings/heat traps installed at the water heater.
    Perhaps the WH was installed without the heat traps, or the heat traps were defective,I just don't know.
    He lives in Texas now, but if I can get in touch with him I'll see if he remembers anything more.
    I could be remembering it wrong, or he explained it to me wrong.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  11. #11
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    Default Re: Water heater circulation pumps

    I've seen the red and blue plastic pieces, I thought they helped to isolate the heat from getting to the supply pipes. I did not know they had check balls inside.
    From your link: Heat Trap Fitting - Vertical or Horizontal Style | Bradford White Water Heaters. Built to be the best.( Removal of these caps allows the balls to travel through the plumbing system creating restriction or blockage. )
    I don't know if this could cause the problem described.



    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

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    Default Re: Water heater circulation pumps

    New construction, something is wrong, have the plumber back in to repair it. Even 5 minutes is too long to wait for hot water.

    Maybe a piece of PEX is floating around, blocking a valve. Maybe lots of things but something is wrong.

    I never see heat traps at the water heater here, but can now say I know about them, thanks, JP.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

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    Default Re: Water heater circulation pumps

    Trent,
    It is a quirk of that system as to how it was installed. The pump will/should act as a check valve for the circulation piping. It is possible/probable that the plumber took a short cut in the installation where the circulation line was not carried to each faucet. But stops short and branches/splits to different faucets. If the pump is not acting as a check valve then there is a possibility that some faucets water is being diverted before arriving to that faucet and is being drawn back to the HW heater. As a side not you may see a circulation system without a pump and only a check valve, on a T, at the HW heater cold water input line.


  14. #14
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    Default Re: Water heater circulation pumps

    You did your job, you found an issue that needs correction. You do not need to solve the issue, we are not plumbers. "Further evaluation and correction from a licensed plumber is needed"


  15. #15
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    Default Re: Water heater circulation pumps

    Sounds like the water heater is on the same floor as the fixtures or above them, unless it hangs in the crawl space? For a return loop to work without a pump, you will need the water heater on the lowest floor possible. If you are on the same floor or higher a pump is needed. Without the pump running you might be siphoning cold water from the bottom of the tank as the cold water enters.

    My water heater is in the basement without any check valves or pumps and it works just fine using the good old gravity loop method. I also have a shut-off valve on the return that is slightly cracked open which allows the effect to happen, this also limits the amount of water that can flow backwards.



  16. #16
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Jerry Peck View Post
    Trent,

    You gave up too soon ... ... that's why the circulation pump was installed.

    You would have gotten hot water to those farthest fixtures if you had waited l-o-n-g e-n-o-u-g-h, but by then your client would have given up and called a plumber, who would have told your client that the home inspector should have caught that, who would then have called you ...

    All the circulation pump did was be patient and just keep pushing hot water through the hot water piping, after heating the copper piping up (if copper) the hot water finally got to the other end, the hot water piping for circulation pumps should be insulated (not sure if it is required where you are, but they still 'should' be insulated to keep the cost of heating the water down, many energy codes require insulation on those re-circulation lines.
    I recently replaced a 10 yo water heater that had check valves [added] to the inlet and outlet. However, those valves may have been supplied by the mfg. I suppose anything supplied by the mfg probably would be threaded into the heater. It would be bad news if the valves were embedded, and then failed. Maybe not bad news to be embedded, because a replacement valve could be threaded in anyway.


  17. #17
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Garry Sorrells View Post
    Trent,
    It is a quirk of that system as to how it was installed. . . . . It is possible/probable that the plumber took a short cut in the installation where the circulation line was not carried to each faucet. . . . ..
    I lean towards Garry's statement above that it is a bad install. But I do think a check valve on the discharge of the recirc pump is necessary just before it ties back into the cold supply to the water heater. If the check valve is not installed, cold water could flow back thru the pump and sometimes even when running does not have sufficient head to overcome the pressure of the city water when a valve is open. Ideally the flow thru a recirc pump is just a trickle and is only required when water is NOT flowing to the faucets.WATER HEATERl.pdfWATER HEATERl.jpg

    Last edited by Rod Butler; 01-13-2014 at 01:00 PM.

  18. #18
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    Default Re: Water heater circulation pumps

    If the "comfort valve" is defective, what you can be getting, is cold water running back and out the hot side. Not actually coming from the Water Heater!
    This would only be true for the faucet where the actual comfort valve is located (normally the furthest from the WH, and may be more than one in a home.

    Turn on the pump and it will force the check valve open and hot water will be supplied.

    Another thing you need to watch for is being too quick on the draw in calling out hot and cold reversed. It is normal for warm water to travel into the cold line and get a few seconds of warm water. And if the water temperature is turned down as in 'Vacation setting' you are more likely to make this mistake. Water from the hot side will run into the cold side till it reaches a sufficient temperature and if it is not hot enough you can get a lot of warm water into the cold supply side and not distinguishable from the hot side.

    Last edited by Larry Morrison; 12-30-2013 at 09:51 AM.

  19. #19
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    Default Re: Water heater circulation pumps

    Hi, all &

    Seems clear an un-powered pump could act as a 'dam' or at least a restriction to water flow. It was obviously installed to boost water flow, by its presence & so it needs to be running...


    Cheers &

    Happy New Year !!!

    -Glenn Duxbury, CHI

  20. #20
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Glenn Duxbury View Post
    Hi, all &

    Seems clear an un-powered pump could act as a 'dam' or at least a restriction to water flow. It was obviously installed to boost water flow, by its presence & so it needs to be running...


    Cheers &

    Happy New Year !!!
    The pump is not where the problem is, it is at the "Comfort Valve" The recirculation pumps are not to increase the flow, but to get Hot water to the far away fixtures without waiting for it. Installing one of these in my house a couple years ago, has made me a lot easier to live with in the morning. And yes, it saves 3-5 gallons of water a day.

    Happy New Year!


  21. #21
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Larry Morrison View Post
    The pump is not where the problem is, it is at the "Comfort Valve" The recirculation pumps are not to increase the flow, but to get Hot water to the far away fixtures without waiting for it. Installing one of these in my house a couple years ago, has made me a lot easier to live with in the morning. And yes, it saves 3-5 gallons of water a day.

    Happy New Year!
    You do save a few gallons of water a day but you are paying for the pump to run and paying for the loss of heat from the piping. I wouldn't look at a recirc system as a cost savings but as a convienience.


  22. #22
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Derek Grace View Post
    You did your job, you found an issue that needs correction. You do not need to solve the issue, we are not plumbers. "Further evaluation and correction from a licensed plumber is needed"

    Figuring out that there is a problem is good. Understanding what caused the problem and how it can be corrected is way far better. Often a problem has a simple solution, but you have to be able to recognize what is required to correct. The more you know the better you will be able to recognize the less than obvious defects and how they may affect other things. Then there is the case where it looks like a repair has been made and all seems fine, without the ability to recognize the incorrect repair method you might just pass it over.


  23. #23
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    Default Re: Water heater circulation pumps

    For simplicity, envision a system with no pump, check valves, etc. just tubing from the water heater to the end use valves.
    There will be two water lines (in addition to the cold water line which I will ignore here) connected at the end use HOT faucet, one is the regular hot water line from the hot water tank to the faucet and another functioning as the return line from the end use water faucet and back to the cold water inlet pipe at the water heater.
    Envision turning on the end use faucet expecting hot water to flow out from the hot water tank.
    But there will be water flowing from BOTH the return line (cold) and the hot water supply line.
    The degree that water flows from each will depend on the restrictions in each line. Now install a running pump and the problem is solved unless there is enough of a pressure differential to overcome the head pressure of the pump.
    Turn the pump off and water can flow backwards through the pump as if there was no pump.
    A check valve in the return line solves the issue.
    The energy trap check valves are a moot point since the cold water return line connects upstream of the water heater connections.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

  24. #24
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    Default Re: Water heater circulation pumps

    Thanks for all the replies. Since the home was built last year, I recommended further evaluation by the plumbing contractor that installed the plumbing.


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    Default Re: Water heater circulation pumps

    You score the points Jim, that was a great explanation.


  26. #26
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Larry Morrison View Post
    The pump is not where the problem is, it is at the "Comfort Valve"
    Larry,

    Okay, new one on me here - what to heck is a "Comfort Valve"? You mentioned it twice, and asserted that it was the problem ... and I don't even know what a "Comfort Valve" is - never heard of it before.

    Jerry Peck, Construction / Litigation Consultant
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    Default Re: Water heater circulation pumps

    Larry may be referring to a Thermostatic Shower Valveor a Thermostatic control valve.


  28. #28
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Jerry Peck View Post
    Larry,

    Okay, new one on me here - what to heck is a "Comfort Valve"? You mentioned it twice, and asserted that it was the problem ... and I don't even know what a "Comfort Valve" is - never heard of it before.
    595926 - Grundfos 595926 - Comfort Valve

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  29. #29
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    Default Re: Water heater circulation pumps

    The water would take the path of least resistance.

    That path may have been backwards out of the bottom of the water heater, through the pump then to the fixture.

    The water displaced by the water leaving the bottom of the water heater is replenished by the cold water intake via a dip tube to the bottom of the tank. You would get mostly cold water at the pump fitting, if the pump was plumbed at the drain. That is where a check valve comes in handy.


  30. #30
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Garry Sorrells View Post
    Larry may be referring to a Thermostatic Shower Valveor a Thermostatic control valve.
    That is what I was thinking of, but if the valve is off there will not be any 'back flow from the cold into the hot'.

    Jerry Peck, Construction / Litigation Consultant
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  31. #31
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Rick Cantrell View Post
    Thanks Rick,
    Should have scratched my head a little harder. May have been that I had put the valve out of my thoughts since it is costly(operation) and problem prone. Haven't seen one in many years. Locally in either new construction or a replumbing situation extra lines are run rather than cheeping out with the Comfort Valve. Did a search for diagram of how it actually works and came up with this that is a good explanation of the Comfort Valve.

    Comfort Valve Hot Water Circulators
    or
    Hot Water Circulation Need To Know Comfort Valve Bypass Valve Sensor Valve Inefficiencies

    The valve is an alternative from running a series of hot water return lines to the tank with a one way/directional valve or a circulation pump. But not a good choice.


  32. #32
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Larry Morrison View Post
    The pump is not where the problem is, it is at the "Comfort Valve" The recirculation pumps are not to increase the flow, but to get Hot water to the far away fixtures without waiting for it. Installing one of these in my house a couple years ago, has made me a lot easier to live with in the morning. And yes, it saves 3-5 gallons of water a day.

    Happy New Year!

    Thanks Larry. Had pushed that valve out of my memory. Kinda of like the bad date that you want to forget. Glad it is working for you. The question is the cost trade off of water against the fuel cost. Have you noticed anything?


  33. #33
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Garry Sorrells View Post
    Thanks Larry. Had pushed that valve out of my memory. Kinda of like the bad date that you want to forget. Glad it is working for you. The question is the cost trade off of water against the fuel cost. Have you noticed anything?
    I'm sure most of the cost trade-off is going to have to be the cost of my time standing there waiting for the shower to heat up...At 45 seconds to a minute a day, comes out to over 5+ hours/year or about the time it takes for an inspection... $400 x 2 (my wife) $800.00/ year. (well in my defense that is closer math than the claims made by the ant-incandescent light bulb greenies)

    And did I mention we live in a desert?


  34. #34
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Garry Sorrells View Post
    Thanks Rick,
    Ditto - never heard of a Comfort Valve before, always learning.

    The RedyTemp is similar to this: Laing AutoCirc Pump which have been around a long time.

    I had a large house in Miami years ago which had a wet bar in the middle of the family room, took about 20-30 minutes to get hot water there after the home was finished. The plumber forgot to install the piping for the recirculation pump loop, he installed one of the AutoCirc pumps after the fact and did the trick.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  35. #35
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Garry Sorrells View Post
    Figuring out that there is a problem is good. Understanding what caused the problem and how it can be corrected is way far better. Often a problem has a simple solution, but you have to be able to recognize what is required to correct. The more you know the better you will be able to recognize the less than obvious defects and how they may affect other things. Then there is the case where it looks like a repair has been made and all seems fine, without the ability to recognize the incorrect repair method you might just pass it over.

    Gary, thank you that is what I was thinking. If we understand an issue it can change what the recommendation is. I try to figure out things so the next time I run into it I have an idea what the problem is and how much of an issue it is. Of course there are always situation we will never know the correct answer. But if we are constantly trying to increase our knowledge of issues and situations then we are much better service to our clients.

    Don Hester
    NCW Home Inspections, LLC
    Wa. St. Licensed H I #647, WSDA #80050, http://www.ncwhomeinspections.com

  36. #36
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    Default Re: Water heater circulation pumps

    Quote Originally Posted by Jerry Peck View Post
    Ditto - never heard of a Comfort Valve before, always learning.

    The RedyTemp is similar to this: Laing AutoCirc Pump which have been around a long time.

    I had a large house in Miami years ago which had a wet bar in the middle of the family room, took about 20-30 minutes to get hot water there after the home was finished. The plumber forgot to install the piping for the recirculation pump loop, he installed one of the AutoCirc pumps after the fact and did the trick.
    I had a friend who put a pump under his sink, and then he got tired of waiting a minute, probably less, for cold water to get a drink, and didn't like the idea of drinking the water out of the tank, so he removed it. My gravity loop returns to the bottom of the tank and works just fine, and is pretty much the only way I see them installed around here, even with pumps, but basements are common. I haven’t encountered an under the sink unit yet, other than my friends, to see if what he said is common.

    Maybe I'm in La-La land, but think I remember reading something about turning the water heater up to 140 degrees, maybe more, to kill bacteria, and then using a tempering valve to get the water temp back to 120 if you use one of those under the sink units. It wasn't a requirement, more of a recommendation, maybe I read it in the literature of the product, or it was just something I read about making water safer. Heck, you probably absorb more water through your skin taking a shower or bath vs. a quick drink, so maybe I am in La-La land...




  37. #37
    Join Date
    Feb 2011
    Location
    Upstate N.Y.
    Posts
    116

    Default Re: Water heater circulation pumps

    Quote Originally Posted by Trent Tarter View Post
    I had a weird thing happen at todays inspection. Place was high end home, new construction, vacant. The water heater has circulation pump, it was unplugged when I arrived. I did not plug it in at first, I could get hot water at one fixture right away. However it took about 20+ minutes before I got hot water in kitchen, still could not get hot water at fixtures that were furthest away from water heater. After I plugged in the circulation pump and waited for 15-20 minutes, I could then get hot water at all fixtures.

    I have never had a situation where I could not get hot water due the circulation pump not being plugged in. Wondering if there's a problem of if this is just how this particular system works?
    Trent,
    I have wired circulation pumps into the hot water plumbing loop to facilitate “demand” hot water systems. Where this has been a practice, the circulation pump is generally wired to a timer so that the water circulation occurs only during times when there may be an actual demand for such. Otherwise, the circulation pump would defeat the purpose of the demand heater by continuously circulating water throughout the plumbing, eventually cooling such by conduction to the copper, etc. and causing the demand heater to heat water that is merely circulating but not being utilized.


  38. #38
    Join Date
    Mar 2007
    Location
    Spring Hill (Nashville), TN
    Posts
    5,847

    Default Re: Water heater circulation pumps

    Quote Originally Posted by Richard D. Fornataro View Post
    Trent,
    I have wired circulation pumps into the hot water plumbing loop to facilitate “demand” hot water systems. Where this has been a practice, the circulation pump is generally wired to a timer so that the water circulation occurs only during times when there may be an actual demand for such. Otherwise, the circulation pump would defeat the purpose of the demand heater by continuously circulating water throughout the plumbing, eventually cooling such by conduction to the copper, etc. and causing the demand heater to heat water that is merely circulating but not being utilized.
    If we are talking about a tankless water heater with just a recirculation pump, this is a problem. In order for a tankless water heater to work properly with a recirculation pump you need to also install a small water heater 5-10 gallons to act as a holding tank. The water actually circulates between the small holding tank water heater and the fixtures throughout the home. The tankless unit only turns on when water is taken out of the loop, it fills the small holding tank water heater....

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  39. #39
    Join Date
    Nov 2007
    Location
    Chicago
    Posts
    548

    Default Re: Water heater circulation pumps

    Quote Originally Posted by Scott Patterson View Post
    If we are talking about a tankless water heater with just a recirculation pump, this is a problem. In order for a tankless water heater to work properly with a recirculation pump you need to also install a small water heater 5-10 gallons to act as a holding tank. The water actually circulates between the small holding tank water heater and the fixtures throughout the home. The tankless unit only turns on when water is taken out of the loop, it fills the small holding tank water heater....
    You can have a recirculation pump on a tankess water heater system without a holding tank. There is two things needed to do this properly. First is a timer set for the demand time of the day. Second is an aquastat, to turn off the pump when the water reaches the set temperature.

    As for any recirculation system be it gravity or pumped, it I ideal to install a swing check(one way valve) If the pump stops running and the inlet water pressure from the cold is strong enough it can flow through the recirculation loop. On proper designed gravity systems, this is unlikely to happen since the return loop is much smaller in size than the hot water supply pipe.


  40. #40
    Join Date
    Mar 2007
    Location
    Ormond Beach, Florida
    Posts
    26,248

    Default Re: Water heater circulation pumps

    Quote Originally Posted by Ron Hasil View Post
    You can have a recirculation pump on a tankess water heater system without a holding tank. There is two things needed to do this properly. First is a timer set for the demand time of the day. Second is an aquastat, to turn off the pump when the water reaches the set temperature.
    Three things needed: Third - the use of a circulation pump which does not state not to use it on a tankless or point of use system.

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  41. #41
    Join Date
    Nov 2007
    Location
    Chicago
    Posts
    548

    Default Re: Water heater circulation pumps

    Quote Originally Posted by Jerry Peck View Post
    Three things needed: Third - the use of a circulation pump which does not state not to use it on a tankless or point of use system.
    Most tankless systems state not to use a recirculation pump unless it has the timer/aquastat installed. I did leave out one part, a properly sized pump to flow the water fast enough to turn on the tankless water heater, but not to fast as to wear a hole in the piping.


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