Hello,

We are installing a new washing machine in an upstairs apartment and I have some questions about running a drain. The easiest route for a drain is to run it down our outside wall, into the basement, and hook into the laundry tub basin that is down there. This would require about a 25ft vertical drop and a 14ft horizontal run.

1st question: is there any requirement as to how close we need to install a trap for this drain? Could we install the trap in the basement?

2nd question: will we need to account for a venting system for this drainpipe? The laundry sink feeds directly into the basement floor and is not vented itself.

Thanks in advance for any help

You're going to love my answer!

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1st question: is there any requirement as to how close we need to install a trap for this drain? Could we install the trap in the basement?

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This hook up requires no trap. (Explanation later)

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2nd question: will we need to account for a venting system for this drainpipe? The laundry sink feeds directly into the basement floor and is not vented itself.

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Ya don't need a vent either.
You laundry indirect wastes into a floor drain and requires no vent. Think of the drain line that you're draining from the washer into the laundry sink, through a indirect waste, as a extension of the discharge hose of the washer, because in effect that's what it is. The only drawback might be bacteria growth in the drain after it's been in use for some time but bleach will take care of that. Good luck, Tom

Thanks for the quick answer!

1 clarification though-- you are assuming that I am emptying directly into the laundry sink in our basement - correct? My only concern with doing this is that our washing machine (the new washing machine is for a tenant) also empties into that laundry sink. If they both ran at the same time, wouldn't that create a problem with overflow?

As I phrased my question, I meant that I would be running the drain line directly into the drain for the laundry sink (underneath) -- and thus would need a trap & vent.. correct? I did make an interesting discovery in our basement -- there is a roof vent that runs into our basement that must have been old -- it is not attached to anything. So, if the first situation (running into the sink itself) does create a problem, couldn't I run the drain line to the basement, run a trap, and right after the trap hook into this existing vent -- then into the sink drain pipe? I hope that's not too confusing...

Thanks again for your help!

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you are assuming that I am emptying directly into the laundry sink in our basement - correct?

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Correct.

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My only concern with doing this is that our washing machine (the new washing machine is for a tenant) also empties into that laundry sink. If they both ran at the same time, wouldn't that create a problem with overflow?

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This would depend on the volume of discharge from both washers, the capacity of the laundry sink and the size of the sinks drain.

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So, if the first situation (running into the sink itself) does create a problem, couldn't I run the drain line to the basement, run a trap, and right after the trap hook into this existing vent -- then into the sink drain pipe? I hope that's not too confusing...

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Well, it's confusing to me! Is the vent you're planing to hook the washer drain into capped off at base forcing you to install a sanitary cross connecting trap to vent to sink drain? That doesn't make any sense. And if you hooked to the sink drain what would prevent a back up if the two washers discharged at the same time. You're still using the same drain for both, just discharging the upstairs washer a tad downstream from the other.
If the unused vent's connected to the main and if you could get to it from the upstairs apartment I would cut in a sanitary tee, trap and stand pipe and keep it all up stares.
Good luck, Tom