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Hot Water recirculating line

Kal Row
Kal Row Member Posts: 1,520
every notice how it's usually the hot water line that freezes rather then the cold water line, that’s because the cold water lines (usually exposed) can convect 45 degree water up from the street, form from exposed areas, whereas the insulated hot water line is thermally trapped – and the water doesn’t move so cold spots freeze

think "density" – cooler water/air is denser thus heavier than warmer water/air and will gravity displace it even in a single pipe – I maintain that if you have a well insulated 2” (maybe even smaller) hot water riser – pitched so that you can single point drain it, then just the uninsulated branches under the sinks will give you enough convective velocity for instant hot water – "a loop in a single pipe" – let gravity be you friend

heat doesn’t rise – it radiates and conducts in all directions – hot air and water has gravity mass and wouldn’t rise either, except that, it gets displaced upward by heavier cooler air or water – that’s the “dirty” little secret of radiant heat, because there is almost no air convection in the room the dust settles and it looks like the house has be unoccupied for months in only one week

had a case with a riser going up an uninsulated brick outside wall, everything was fine because the basement ceiling was exposed and allowed for convention – however the was a 1ft run from the riser to a speedy under the sink at a 10 degree down angle – which of course froze and broke since it could not convect it cooler water away – I don’t shut my hose connections for the winter - I piped them all upwards and just open a panel underneath them and let gravity do it’s thing - before I did that, I had a feeze bust in the line behind the inside shutoff that wasn’t pitched right – if all houses could be single point drained – there would only be a freeze bust during a complete power

this is why we liberally sprinkle our heating systems with spring check valves , imagine the heat from the boiler and indirect hot water system migrating up unchecked zone returns, wasteful in the winter, really really gets customers mad in the summer

Comments

  • John Fernandez_2
    John Fernandez_2 Member Posts: 40
    Hot Water recirculating line


    I am installing the plumbing in a two story home, domestic water lines are to be type-M hard copper, heating system is to be radiant with a hot-water maker attached to the boiler, which will be installed in the basement. Question is this, what is the best way to make certain that I have hot water at the upper fixtures without running /wasting alot of water, in other words i need to do a recirculating line but I DO NOT want to use a circulator pump, how do I do this ??????
  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    Newtonize it!!

    Here's a link to Dave Yates article addressing this very need. http://www.contractormag.com/articles/column.cfm?columnid=62

    And here's a link to a host of other articles written by the Yatester himself. http://www.contractormag.com/articles/columnist.cfm?columnistid=1

    Enjoy!

    ME

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  • ScottMP
    ScottMP Member Posts: 5,884
    Marks got it.

    Read Daves articles and use gravity to circulate your domestic. Insulate your hot water lines, you can loose alot of temperature on the re-circ. line.

    I would think hard and long about switching to type L copper for your domestic water. Unless of course your interested in re-piping in fifteen years or so.

    Scott

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  • Kal Row
    Kal Row Member Posts: 1,520
    another advantage of a gravity loop is freeze protection...


    every notice how it's usually the hot water line that freezes rather then the cold water line, that’s because the cold water lines (usually exposed) can convect 45 degree water up from the street, form from exposed areas, whereas the insulated hot water line is thermally trapped – and the water doesn’t move so cold spots freeze

    think "density" – cooler water/air is denser thus heavier than warmer water/air and will gravity displace it even in a single pipe – I maintain that if you have a well insulated 2” hot water riser – pitched so that you can single point drain it, then just the uninsulated branches under the sinks will give you enough convective velocity for instant hot water – "a loop in a single pipe" – let gravity be you friend

    heat doesn’t rise – it radiates and conducts in all directions – hot air and water has gravity mass and wouldn’t rise either, except that, it gets displaced upward by heavier cooler air or water – that’s the “dirty” little secret of radiant heat, because there is almost no air convection in the room the dust settles and it looks like the house has be unoccupied for months in only one week

    had a case with a riser going up an uninsulated brick outside wall, everything was fine because the basement ceiling was exposed and allowed for convention – however the was a 1ft run from the riser to a speedy under the sink at a 10 degree down angle – which of course froze and broke since it could not convect it cooler water away – I don’t shut my hose connections for the winter - I piped them all upwards and just open a panel underneath them and let gravity do it’s thing

    this is why we liberally sprinkle our heating systems with spring check valves , imagine the heat from the boiler and indirect hot water system migrating up unchecked zone returns, wasteful in the winter, really really gets customers mad in the summer
  • Dave Yates (PAH)
    Dave Yates (PAH) Member Posts: 2,162
    Newtonize it!

    I like the sound of that phrase(G). Thanks guys. Newtonian physics. It ain't rocket science, it's applied science.

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  • PLUMBERPIERCE
    PLUMBERPIERCE Member Posts: 9


    yes sir, thermalsyphon physics is never wrong and i would use grade L tubing.
  • Kal Row
    Kal Row Member Posts: 1,520
    i did want to mention \"L\"...

    only those of us with real world experiance know about prematur failure and pipe erosion - a HomeOwner will think your just trying to "sell them something" - i never us M and stay away from those thin chinese fittings - eapecialy now that the chinese have forced NIBCO's prices down
  • BillW@honeywell
    BillW@honeywell Member Posts: 1,099
    An alternative...

    Check out the package Grundfos has. Its a timer, pump and a by-pass valve. The bypass is installed on the fixture that is last in line and the pump & timer get installed on the water heater. The timer starts the pump at a pre-set time, circulates the water, and then shuts down at another preset time. Team this with one of our AM or AMX mixing valves & you have a safe, comfortable & water saving system. Don't forget to insulate the pipes!
  • ALH_3
    ALH_3 Member Posts: 151
    Occupancy

    Depending on your reason for not wanting a pump(off grid?), you could use occupancy sensors in the bathrooms to turn on a small recirc pump for a preset length of time. If you dont walk in the bathroom you dont keep the lines hot. This saves energy in the form of standby loss in the recirc line, which can be significant. Using a pump gives you a lot of control you dont have otherwise.

    -Andrew
  • BillW@honeywell
    BillW@honeywell Member Posts: 1,099
    Great idea!

    An occupancy sensor is a fantastic idea, only drawback I could see is a lot of cycling, especially with kids.
  • Joe Mattiello
    Joe Mattiello Member Posts: 703
    Try Taco D'mand system

    The D’mand pump is perfect for retrofit applications. Circulator is installed under the vanity, with a push button activator. Circulator energizes pumps water into the cold water supply line as the return back to the heater. There is a thermistor in the pump that will shut the pump after a 5 degree temperature rise, so hat water is not wasted. For your reference I have attached a catalog.

    Taco, Inc.
    Joe Mattiello
    Technical Service Technician
    [email protected]
    401-942-8000 X 484
    www.taco-hvac.com
    Joe Mattiello
    N. E. Regional Manger, Commercial Products
    Taco Comfort Solutions
  • Jimmy Gillies
    Jimmy Gillies Member Posts: 250
    Gravity HW return line.

    Dave,
    Could you(or anyone) kindly email me your drawings showing the HW return lines & the brass swing check valve. I read your article with great interest.
    It's funny, here in the UK it's only over the last 8-10 years that we stopped using vented HW systems(with copper cylinders & plastic tanks in the attic, being the order of the day).
    We are now looking for good reliable HW return systems for our larger homes.
    Thank you very much.
    Regards.
    Jimmy Gillies (Scotland)
This discussion has been closed.