Condensate drain details

[davidj]

The vent on my tankless water heater has a connection for draining condensate.  The venting kit also included some 3/8 ID silicon tubing, which apparently I tie in a loop to make a baby S-trap.  The bit I'm stuck on is where do I take it from there?  I get the impression it needs to go into the DWV system, but I'm not sure where to connect it in.  Does it need an addition dedicated P-trap in the DWV?  Or do I somehow tap into an existing trap, perhaps in the vanity?  Or can I just connect it straight to the DWV system, e.g. the vertical drain behind my vanity?  Note I haven't got any floor drains in the cabin, just a toilet, vanity and bath.

Alternatively I can take it to the outside, but I guess that'll probably freeze and I'm not sure dripping out acidic water by my deck is the best way to go...

[Shawn B]

If the plumbing will not be inspected I would drain it into the lav drain DWV pipe. To do this drill a hole in the pipe, then tap it with a 3/8 NPT or  1/2" NPT (National Pipe Thread). Drill this hole on the top side of the pipe. Tap the hole as needed. Screw in a threaded hose bard adapter, use teflon tape or thread sealant, hose clamp the tube and your done. Be sure to form a Loop trap up at the water heater vent. zip tie it so it won't come undone.


If in a code compliant area I would drain the condensate under the lav sink, but inside the lav cabinet. To do this get a dishwasher Y fitting and one of those stepped rubber connectors. The one that has multiple sizes and has hose clamps on the ends. You remove the old P-trap install the Y fitting then reinstall the P-trap as required. The down side is you will probably need a condensate pump for this type of application, unless you can gravity drain it?

I have done many, many furnace and A/C condensates this way.

[davidj]

Thanks a lot for the info Shawn - just what I wanted to know.  I'm gonna be inspected but the good news is I can easily gravity-drain it to the lav P-trap (the water heater is right next to the lav, and the heater's at head height).  However I guess I'm not allowed to put polyethylene or vinyl pipe in the wall (for maybe 12"), so do I need to transition to pex for a few feet?  I was originally planning on flexible copper, but apparently that's not good for the acidic condensate from a vent...

[Shawn B]

I would transition to 1/2" sch 40 pvc for the length in the wall. Pvc is less likely to clog up than the smaller I.D. pex pipe. If you use pex go with 3/4", though the pvc should be less cost.


I'm thinking is this the only condensate drain for the water heater? Or is it a secondary drain? The reason I ask is some furnaces have a secondary drain just for the vent, plus the main drain for the unit.

[davidj]

I would transition to 1/2" sch 40 pvc for the length in the wall. Pvc is less likely to clog up than the smaller I.D. pex pipe. If you use pex go with 3/4", though the pvc should be less cost.

I'm thinking is this the only condensate drain for the water heater? Or is it a secondary drain? The reason I ask is some furnaces have a secondary drain just for the vent, plus the main drain for the unit.

It's the drain just for the vent, so I think it's pretty low throughput.  There's no condensate drain on the main unit as far as I can see (it's a Takagi TK-3 with z-flex venting).