Can anyone show me a diagram of a "crossover" line for quik hot?

Discussion in 'Water Heater Forum, Tanks' started by bsa_bob, Sep 1, 2012.

  1. bsa_bob

    bsa_bob DIY Member

    Messages:
    56
    Location:
    britton mich
    Please ignore the 6 gallon thread i posted below. I couldn't find how to delete it, This is my preferred thread. I am an "ole retired journeyman plumber".

    I need someone to post a diagram of a "crossover" installation to get quick hot water. and what parts i need to install. i don't want a re-circulation pump, situation if this cross over will serve me and her, and stop wasting 120 feet cold cold water every morning
    please feel to share what you have on this. My email can be use also scharpr@ymail.com thank you fellas bob s
    Last edited by a moderator: Sep 30, 2012
  2. Gary Swart

    Gary Swart In the Trades

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    7,387
    Location:
    Yakima WA
    This is a product that installs under the sink that works pretty well. I thing is called, "Ready Hot" or something similar. I assume you have a reason for not installing a recirc with pump, that really works great, but of course it does need a return line which might be the problem in a retro fit.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,270
    Location:
    New England
    You need to the water to circulate if you want 'instant' hot water. If you can afford to wait, and request it, you don't need to run the pump constantly. There are ways to activate the pump from multiple locations, if that's an issue.

    If your piping layout will support it, it is possible gravity convection will keep the water warm (not hot, especially over 120-feet!). This would require a dedicated return line and a check valve back to the WH.

    IF, and this can be a big if, you can get power underneath the sink in the furthest location, you could install what I have - a RedyTemp unit in about 10-minutes for a typical install. It is a self-contained pump, cross-over, check valve system. It's on the higher end, but it is really easy to install. I have one, and it has been working fine for pushing 8-years now with no maintenance. I have it on a timer, so it doesn't run while I'm typically sleeping, but it is fairly easy to setup to work via remote, or to bypass the timer entirely.

    All systems require a cross-over, and you may need or want more than one. The more typical units have the pump back by the WH, since there's room and typically power nearby. Then, they put a cross-over at the needed sink(s). If you don't have dedicated return line(s), and you use a pump, it uses the cold water line as the return via the cross-over/check-valve. This means that when the valve is open, the cold water will end up warm until the aquastat in the cross-over closes the valve (and for awhile as it cools). The RedyTemp unit has a user adjustable cutoff point. I have mine set to have warm water at the sink...my shower is closer to the supply, so gets nearly instant hot. And, flushing the low-flow toilet pretty much clears the warm water from the cold line since I have it set to only get warm to the sink instantly (hot isn't far behind, though).

    To make a gravity convection system work, the lines have to be sloped properly with no jogs (at least no upwards excursions) in the return line, or that will stop the convection. This can be hard to do, especially over 120-feet as you also need to slope it for best results. Without a temperature gradiant, there's no density difference, thus, no convection - just conduction, cooling the pipe off along with the water.

    Personally, I think you'll find it really hard to get a convection, pump-less system to work over 120-feet from the supply to the point of use.
  4. bsa_bob

    bsa_bob DIY Member

    Messages:
    56
    Location:
    britton mich
    Thank you jadnausha..Ill make a copy of this to read awhile and think about. s they say old plumbers never die they just fade away .....or was that indians anyway thank you for the help This job will refresh the "plumber in me" bob s
    Last edited: Sep 1, 2012
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,270
    Location:
    New England
    If this is a ranch, and things are all on the same level, you may never get enough flow from convection to make it work...you'll need a pump.
  6. bsa_bob

    bsa_bob DIY Member

    Messages:
    56
    Location:
    britton mich
    Thank you all for the help.believe me i hadn't realized how much knowledge i had forgotten being a plumber.I am now thinking on a instant hot.
    / tankless water heater mounted in the basement under the k/s. This is the only thing on the far end of the house[from the water heater]---that she needs hot water rather quickly. Is this 2 gallon set-up-or what do you recommend in size] going to work for her and i....maybe a handful of people on the holidays. I mean ...will this suffice for the clean-up and the preparation of meals for her and i mainly?If so how much should i put into this small wall mounted w/h???
    thank you can for helping me. bob s

    ps thanks jad the convection set-up is now off the table.for cosideration bob
    Last edited by a moderator: Sep 30, 2012
  7. LLigetfa

    LLigetfa DIYer, not in the trades

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    4,158
    Location:
    NW Ontario, Canada
    I don't know why you are dismissing a recirc pump. They use very little power and there are different versions available. If you don't drink cold water straight from that tap, then the existing cold water line can be used for the return. One version of recirc gets installed at the sink and can be activated by a push of a button. It will pump from the hot line into the cold line, stopping when it senses hot water. Another version gets installed at the HWT and remote "crossovers" get installed at any sink you want instant warm water at. The remote crossovers sense the heat and stop the crossover flow.

    A tankless water heater requires a large gauge electric cable under the sink.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,270
    Location:
    New England
    If you can provide enough slope and a return line, if the WH is below the floor where the kitchen is, you might get by with a gravity/convection loop. The supply pipe probably makes too many jogs to allow it to work, though. But if it did, the flow would be slow, and over 120-feet, it probably would only get warm, not hot. Having a dedicated return line IS a good idea, though, even with a recirc system. By far, the simplist thing would either be a small under counter WH, or a recirulation system. The tank size would have to be big enough to surivive the dilution of the incoming water before hot arrived. Depends on the size of your supply line how big that would need to be. This assumes that you need enough to exhaust the tank. For small draws, you could get by with a smaller tank. The recirc system I have would only take 10-minutes to install assuming you have a spare outlet under the kitchen sink (fairly common, or easy to add). Basically, you disconnect the hoses to the shutoff valves, attach them to the outlet of the recirc system, then install new hoses from the shutoffs to the inlet of the recirc system, then plug it in and you're done. WOrks great, lasts a long time, uses little energy.
  9. bsa_bob

    bsa_bob DIY Member

    Messages:
    56
    Location:
    britton mich
    Hi jim Would you elaborate on the model you have, brand ,etc and where i can get one. Ithink it will serve me and her well thanks jim bob s ps my pc has been down a long time ......reason for not returning your reply
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,270
    Location:
    New England
    http://www.redytemp.com/main.php They have more models than when I bought mine (the Optimizer). I bought it direct, but there may be other resellers now where you might get a better price. It requires you have power where you want to install it, and you may need to add an outlet underneath the vanity. In my case, I was remodeling, and it was easy to just drop down from the existing box to a new one in the back of the vanity. This is the easiest one to install around, has some advantages, but does cost more than many of them. Mine's in the order of 7 years old and going strong. I have an electronic timer hooked up to it programmable with 7 individual days. You may not need that flexibility, and I don't now since I'm retired.

    Most systems get installed near the WH, and the cross-over device(s) get installed at the desired fixture(s). I liked this one because of the adjustability (on-board aquastat) and the ease of installing a timer. On most, the pump runs constantly, and the cross-overs open/close as needed to maintain the set temp of the water there. You can put the whole thing on a timer. This one only runs the pump when the aquastat calls for it. This means more wear and tear since it is turning on/off all the time. In my case, it seems like it runs for maybe 60-90 seconds about every 15-minutes, but I have it set to provide warm water at the vanity...the shower is closer to the WH, so it is hot almost instantly. I find that if I flush the toilet, once that has refilled, I then have cool water in the cold line, prior to that it is warm. This is fine with me, as most of the time the toilet does get used before I need to use the sink, and the shower gets hot right-away, regardless.
  11. bsa_bob

    bsa_bob DIY Member

    Messages:
    56
    Location:
    britton mich
    I have decided on a 3 or 4 gallon ,heater just under the floor beneath the k. sink. Can you suggest any national preferred brands to me jim. If they don't let this note go thru Please email me at scharpr175@ymail.com thank you/ bob
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