I'm looking to replace "Nuvo Home" with a Aquasure salt-based water softener (Harmony Series 48,000 Grains). Installation process seems to be straightforward, but I'm not sure where the drain line should go in my garage. There's no floor drain, but my Navien tankless water heater's condensation drain line connects to a tube coming out of my drywall as shown on the picture.

There's actually another tube, which is cut and open (not connected to anything). The previous home owner had a salt-based water softener which he replaced with Nuvo home, so it's possible that the open tube was previously connected to drain of water softener.

My question is, what would be the proper way to connect drain line from water softener?

  1. Connect the drain line to this "open" tube, if it's connected to drain. Is it a common practice to leave a tube unconnected like this, maybe to function as an airgap?
  2. Put a Y-splitter in the green arrow so that drains from both water softener and heater are connected to the same tube?

My apologies for improper terms (I'm a newbie). Any help would be greatly appreciated!

enter image description here

  • 1
    did they fish that tube to something on the other side, both emptying outside perhaps? then you could just feed the softener into that cut off black piece, which is likely what it was before
    – P2000
    Sep 15, 2021 at 5:13
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    Thanks for your reply, @P2000. The problem is, I moved into this house after they did the plumbing, so I don't know what they did to install these two tubes. Is there any way to quickly test whether they're going to the drain?
    – Brian C
    Sep 15, 2021 at 6:33
  • 1
    Note that you will likely need a significantly larger hose for a softener drain than for a little condensate.
    – SiHa
    Sep 15, 2021 at 15:27
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    In terms of draining flow (as @SiHa points out for the softener), the Navien needs a 150psi pressure relief valve, ideally emptying into a 2in drain, but I don't see that drain in the picture.
    – P2000
    Sep 15, 2021 at 16:04
  • 1
    Thanks, @P2000. You definitely got me on the right track; turns out both tubes are connected to drain of bathroom sink behind the wall.
    – Brian C
    Sep 16, 2021 at 0:05

1 Answer 1


Since you don't seem to have any problems with leakage from the condensate drain, you know that line goes somewhere safe - i.e. through plumbing and out of the house.

The purpose and destination of the other cut piece of tubing is speculative on your part, and there's no telling where it may go. It's possible that the other end was cut and left loose in a wall somewhere. It's also possible that it too goes into a drain line and safely out of the house.

You could, as suggested in a comment, pour water into that open end to try to listen for where it goes. However, you have to be willing to accept that it could have been cut and left dangling in a wall somewhere, and the water you pour in here could be dumped out into a wall cavity somewhere else. The likelihood of this is probably low, but you would have to assess your willingness to take the risk of potential drywall damage and repair vs opening up drywall to trace the line (with guaranteed drywall repair).

Based on these conditions, I would use the known good line and tap into the fitting indicated by your green arrow. Note that you would need to install a Tee fitting, as I don't believe they make Wye fittings for this size tubing. (If they do, I'd use a Wye, but I don't recall ever having seen one at my local big-box stores. Maybe a plumbing outlet would have one.)

Do be sure that the tubing size meets the requirement specified for your new water softener.

  • "the water you pour in here could be dumped out into a wall cavity " yes, be cautious. Good to see an answer...;)
    – P2000
    Sep 15, 2021 at 15:54
  • 2
    Thanks! I was able to trace the tube and turns out both of them are connected to drain of bathroom sink behind the wall
    – Brian C
    Sep 16, 2021 at 0:06

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