Draining Condensate into Sewer Line
Kenner55
| Posted in General Questions on
The mitsubishi split air manual suggests routing the drain tube to drip outside. Is it possible to drain the condensation into a sewer line with a “p” trap?
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Replies
Yes. I think it’s preferable.
Less moisture around your foundation and (if routed inside)less drain lines too look at outside.
Yes, the drain is fine for Mini-Split condensate, but not for gas furnace condensate.
But you want an air gap, not a trap. During the season when the MS is not used, the trap will dry out, and you don't want sewer gases back into the house.
You need both. The air gap won't stop the sewer gases from coming in the house so you need a ptrap. You can put water manually in the trap to keep it wet or install a trap primer.
The point of the air gap is to stop water from backflowing in your minisplit in case there is a clog in the drain.
Ideally, you can drain it via an existing trap so that the trap doesn't dry out when it's not producing condensate. My condensate drain is plumbed to an Oatey Moda washing machine box, for which they make a clever funnel to allow the same drain to take the washing machine output as well as a condensate drain from the top.
If you have proximity to a sink, you can buy a sink tail piece that has a fitting to accept a condensate drain line. Or, if it's a slop sink, just have it drop right in there.
FYI I have a condensation pump to drain my Combi propane boiler. It fed a small plastic tube outside, right next the the exhaust vent. It froze solid one year right at the tip of the tube.
I rerouted it to a drain in my slop sink, indoors.
You can drain the condensate into any handy drain -- a laundry tub, nearby sink, floor drain, etc. If you install a drain just for the condensate, you do need both a trap AND an air gap as others mentioned. The purpose of the trap is to keep sewer gases from getting into your home. The purpose of the air gap is to make sure you don't have any siphon issues or backflow into the condensate line. The usual way to accomplish the air gap is to put a short piece of pipe up from the trap, then tie the condensate line so that it pokes into that pipe a few inches or more, but not all the way into the water of the trap. You can also get very small bowls that you can glue into the pipe to create a sort of "sink" that condensate lines can drain into. Either way works just fine.
Bill
You can not drain into any handy drain, as you assume. In some areas this is forbidden on the assumption that sewer is for sewer only. Further, on large data centers condensate can be a considerable amount of water, and may be sent into sewer After It Is Metered, To Allow for Billing.
I like to see the condensate piped so that it keeps the floor drain trap primed, this kills 2 birds with one stone.