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Thread: looking for info on laundry room floor drain

  1. #1
    DIY Junior Member acr_scout's Avatar
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    Default looking for info on laundry room floor drain

    I guess this is a two part question.

    The first, the local code does not require a floor drain in the laundry but being paranoid as I am I want a floor drain. What are some of the pros and cons of a floor drain.

    The second, if a floor drain must have a P-trap for sewer gases how do you keep the trap primed? From what I understand, the floor drain needs a dedicated line to the main drain for the house.

    Now a side question but I believe this is legal, can I vent the floor drain back into the washer drain vent above the washer drain?

    Thanks,
    Fred

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    Forum Admin, Expert Plumber Terry's Avatar
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    The floor drain would have a p-trap to prevent sewer gas.
    It would need to be vented, and the vent can tie back into the washer vent, at 6" above the flood level of the fixture.
    The floor drain would need a trap primer to keep it wet.
    Two ways to do this are"
    A dedicated trap primer connected to the water supply.
    A tee on the standpipe of the washer that diverts water to the p-trap. Everytime you run a load, a bit of water would wind up at the p-trap from the water being discharged.

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    DIY Junior Member acr_scout's Avatar
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    Thank you for your input.

    Will the floor drain need to be plumbed all the way back to the main drain by itself or can it be run into the drain for the washing machine?

    The run back to the main drain is about 40 linear feet and at a 1/4" per foot that is a big drop. Any comments?

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    Plumber Esquire's Avatar
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    Quote Originally Posted by Terry View Post
    A tee on the standpipe of the washer that diverts water to the p-trap. Everytime you run a load, a bit of water would wind up at the p-trap from the water being discharged.
    Is this in the code or is it just another way that people have derived from years of experience? Would you just invert a tee or or even a dishwasher wye and then connect that to the trap seal primer inlet?

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    Moderator & Master Plumber hj's Avatar
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    Depending on where the floor drain is in the building, you could run a line from it to the exterior of the house, or into the garage (through the "step up"), and not need a "P" trap OR trap primer. If you do connect it to the house system, it needs to be done just as if it were a sink or any other fixture, with the added requirement for a trap primer. And since few trap primers work as advertised you might still have to pour water into it periodically.

  6. #6
    Homeowner geniescience's Avatar
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    Pro: water has a place to go, when you clean up which happens often, and if anything springs a leak which may only happen once but causes massive disturbance.

    I have floor drains in my bathrooms. I put them far off center so they are less visible.

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