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Just moved into this house, South Florida, two stories, the heater is leaking and I'm replacing it with a tankless. I'm not sure how to plumb it since now I realized I have more pipes coming and going from the existing tank than what I expected, and I don't see a pump. I'm suspecting there is some sort of recirculating but I don't see a pump anywhere.

I have five pipes that go to/from the wall

  • THREE behind the tank (top) - one pressure valve, one of the cold water, one hot water
  • TWO behind the tank (bottom) - another cold water, one that wraps around the tank and connects to the drain valve in front of it.

So, this is tankless heater I bought. How do I pipe this thing? My questions are:

  1. For the cold water, there is a T right now, do I keep the T and basically plug what's going into my existing tank into the tankless?
  2. Same question for the hot water, do I just do a one to one replacement and connect the output from the tankless to my existing hot water pipe?
  3. What do I do with the pipe that wraps around the tank now? Not sure what it does? Should I just cap it and call it a day?? I suspect this is just a drain line since both valves are shut off, the one of the left obviously is to drain out the tank but the valve on the right is also shut.

I also made this video that shows the whole thing.

THANK YOU!

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gnr5
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  • A hot water recirculation system perhaps?? – jwh20 Mar 22 '21 at 13:21
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    Pump may be hiding under a remote sink - fairly common to stick the pump at the furthest fixture, so it can pump until hot there, then stop. Still seems like an extra line, but we don't know what the last plumber was thinking. If you shut both of the cold valves on top does the cold water in the house stop, or not? Wondering if they have the cold feed passing through, to explain that extra pipe. You say both valves on the bottom are closed already... – Ecnerwal Mar 22 '21 at 13:29
  • @Ecnerwal - I cannot find a pump anywhere in the house, so in a turn of events, I turned off the cold valve and now I don't get hot water in the house. Both pipes on my tank, the hot and the cold one, feel warm to touch. – gnr5 Mar 22 '21 at 15:22
  • Added another picture. Thanks! – gnr5 Mar 22 '21 at 15:25
  • So, just realized that this thing is plumbed backwards (if shutting down that valve doesn't return hot water) – gnr5 Mar 22 '21 at 19:34
  • I hate to break this to you, but you're not allowed to use white wires for hot in conduit (unless they are part of cables that are in the conduit). Those white wires have gotta go, and be replaced with colored wires (and more black is fine). Also, you need to group or distinguish the 4 individual circuits... for instance one heating element can't be fed by the L1 off one breaker and the L2 off another breaker. 1 breaker per heating element. I prefer to use colored wires for that... – Harper - Reinstate Monica Mar 22 '21 at 19:43
  • FWIW if you flow about 2 gallons of hot water, the cold pipe should be outdoor-temp, and the hot pipe should be hot-water-temp. That should tell you definitively; I wouldn't care much what the last guy did. – Harper - Reinstate Monica Mar 22 '21 at 19:49
  • The wires are all 8/2 gauge wire, I bought a big roll and inside they happen to be black and white. They are separated by breaker – gnr5 Mar 22 '21 at 20:45
  • @gnr5 -- they're 8/2 cables (NM/Romex(tm)). If you're working in conduit, you need to use individual 8AWG THHN wires instead (for instance: two blacks, two reds, two blues, two yellows) – ThreePhaseEel Mar 23 '21 at 00:24
  • Yes you can... https://diy.stackexchange.com/questions/31149/can-romex-nm-b-cable-be-run-through-conduit – gnr5 Mar 23 '21 at 02:37

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