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Thread: Laundry drain conundrum - drain CWM into bathtub?

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    DIY Junior Member vga4life's Avatar
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    Default Laundry drain conundrum - drain CWM into bathtub?

    Pardon my ignorance - I'm a professional computer geek, not a plumber.

    I recently bought a condo apartment in Seattle and want to install a compact ventless clothes washer dryer combo unit to avoid trips to the basement laundry room. (Nothing in the bylaws limits my right to do this, fortunately.)

    Naturally, the drain's the rub.

    I have a walk-in closet that happens to be directly under the water heater (overhead in the storage loft so access to hot and cold supply is not a problem) and shares a common wall with the foot of the bathtub.

    This gave me the idea of fixing the drain hose to a "dummy" tub spout (or otherwise running the hose through the wall) to drain into the bathtub. It seems like this would adequately provide for an air gap and the tub's ample capacity (many times that of the small front-loading washing machine) would adequately buffer the drainage flow over time.

    Would this be a realistic alternative to spending many kilobucks cutting willy-nilly into the walls and/or subfloors to find and plumb into drains and vents? If not, why not?
    Last edited by vga4life; 04-23-2006 at 07:09 PM.

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    In the Trades Bob NH's Avatar
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    The essence of engineering is to find the most economical way to satisfy the functional requirements while ensuring safety and all that stuff. Just make sure the washer drain is adequately secured so you don't flood anyone downstairs.

    Now I'm sure there are lots of reasons such as the fact that it isn't permitted by the Universal Plumbing Code, but I can't think of a technical reason that it wouldn't work fine. Just don't tell anyone in your condo about it. And make sure that you regularly check the tub drain to make sure it doesn't plug with lint and overflow on the fourth load.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    The drain should work, but I'd be worried about the moisture from the drying cycle. That can be significant, and the lint trap doesn't catch everything, either. Blowing lint into the house can be a health hazard. Is there a window you could put it out on a temporary basis?
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member vga4life's Avatar
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    Quote Originally Posted by jadnashua
    The drain should work, but I'd be worried about the moisture from the drying cycle. That can be significant, and the lint trap doesn't catch everything, either. Blowing lint into the house can be a health hazard. Is there a window you could put it out on a temporary basis?
    The units that I'm looking at use condenser dryers that don't vent the moist air - it's condensed out and sent down the drain (hence "ventless"). Quite common in Europe and Asia, virtually unknown in the US.

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    Moderator & Master Plumber hj's Avatar
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    Default dryer

    IF you can find a dummy tub spout that will handle the washer's discharge flow, and can live with the lint in the tub, then go ahead. But since your "drain" is the open tub, the dryer's condensate is going to be in your bathroom, not down the drain with the lint.

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    Plumber jimbo's Avatar
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    hj, these things actually work quite well. The moist air is condensed into water, so no matter if you put it into the tub, it is still water and drains away. You do not have moist air going into the room. There is of course energy cost, and probalby some waste heat, but the units are small and quite functional.

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    Homeowner geniescience's Avatar
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    Default You found the best solution possible

    Vga

    I admire your ability to hit on the right solution considering all the constraints. In a little while you may have figured out how to get the drain hooked into your bathtub plumbing so you won't need to break the drywall (or tile) to put a hole in the wall to let your washer dryer drip into the tub. This will bypass the tub, but still make noises since it will put the water into the drain above the tub's P-trap (siphon). Technically still not up to code.

    To get to code, you'll need another P-trap, at any height you like, with its drain going into the tub's drain below (downstream, past) the tub's P-trap. Assuming your condo building is not so big that the code would ask for a separate drain line for the Washer-dryer. Since a person can only have so many drains on a single line of a certain diameter before they are required to run a new separate line or else replace the entire line with a wider diameter pipe. And a washing machine counts for more "Units" than just a sink.

    So in practical terms your washer might just cause the drain line to be overloaded some day when everyone else is draining their tub or shower. It could happen. That is what code is for. Nonetheless, don't let me scare you off. I'm just sharing with you the information I think I know, trusting that you will soon find it out anyhow some other way, and that you will make your own judgements and assessments.

    David

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    DIY Junior Member vga4life's Avatar
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    Quote Originally Posted by geniescience
    I admire your ability to hit on the right solution considering all the constraints. In a little while you may have figured out how to get the drain hooked into your bathtub plumbing so you won't need to break the drywall (or tile) to put a hole in the wall to let your washer dryer drip into the tub. This will bypass the tub, but still make noises since it will put the water into the drain above the tub's P-trap (siphon). Technically still not up to code.
    Even if the common wall was on the same side as the tub drain, I'd worry about plumbing the CWM directly into a tub drain that might not be able to handle the flow rate.

    Unless by some miracle there's a 3" drain line and vent in that closet wall, I think i'll be going the tub spout route if I can find a good plumber willing to help me run the supply lines down. I can't afford to learn to sweat copper myself on this project and risk flooding the commercial tenant below me.

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    In the Trades Gary Swart's Avatar
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    Just a comment about sweating copper. This is extremely simple and should cause you no problem whatsoever. There is of course the expense of a torch, solder, and flux. I think soldering is easier than compression joints which also require some equipement.

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    Homeowner geniescience's Avatar
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    Default Same size diameter for Tub drain and washing machine drain

    vga

    Seems like neither one of us is an expert on the plumbing Code.

    I do know this much: the diameter (i.e. size) of a drain is designed by code to be truly sufficient and even a little bit too much in order to handle the worst situations. Each drain is the size it is for a reason. I also know that it is against Code to put in a drain that is two or three sizes larger than the prescribed size. I also know that a 1.5" diameter drain is the size for 1. a tub, 2. tub-shower cominations, 3. a washing machine, and 4. a washing machine with a laundry sink nearby plumbed into the same drain. I also know that each available size carries about twice as much volume as the smaller size pipe.

    So I conclude that it is against Code to use a 3" pipe as a drain for a tub or a washer. Hope this helps.

    All washing machines drain into a pipe which is 1.5" in diameter. The 1.5" diameter pipe that is already in place, for the tub, is the same pipe. When a tub drain AND a washer drain, both 1.5", combine, the next size up, 2", is used to carry the two drain flows together. That 2" pipe flows into a bigger pipe whic carries your waste water with other neighbors' too.

    Also, please realize that copper sweat solder is not a challenge, and drains do not carry pressurized water which is the kind that causes floods. Flooding is not a risk. You can make a seal with copper, and let drain water flow though the pipe, without worrying about a future flood. You can inspect your seal visually. You can test run it. You can keep coming back to it and checking for minor leaks. That is the extent of the risk. My opinion.

    David

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    I thought I read that washing machines require a 2" drain...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    In the Trades Bob NH's Avatar
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    I think the first idea of dumping the water in the tub is the best one. The tub has plenty of capacity to avoid overflowing. When the water gets deep in the tub it will have more head to discharge through the 1.5" drain. Anything else is more complicated, more expensive, and unnecessary.

    Since laundry is an occasional use vga4life could get a flexible hose that is a bit larger than the normal washer hose and run it over the floor on wash day, and roll it up and put it away later. But I thing the first idea was best.

  13. #13
    General Contractor Carpenter toolaholic's Avatar
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    yes laundry sinks and washers require a 2' trap , but

    this is a bootleg suggest you invest in a good rubber mat to keep the washer vibration down.

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