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Washing machine drain solution

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  • mattmia2
    mattmia2 Member Posts: 16,462

    you would support the cast iron stack be fore cutting it then leave the support after you're done

  • hot_rod
    hot_rod Member Posts: 27,329

    the trap arm is the length from the trap to where the vent takes off. Codes vary, but 5-8’ is typical length.

    In your case the is no vent before the WC connection, so when you flush the shower trap may siphon some. If so you end up with sewer gas smells.

    The vent taken off a horizontal grain line should be above the centerline if the drain, also.

    IMG_1437.jpeg

    you could cut a 2” y into the shower trap arm, wet vent the washer into it. Not exactly legal but it solves two issues. It gets you a 2” washer drain and vents the shower drain.

    1-1/2” washer drains were allowed in codes for many years. If the washer discharges 9 gpm or less, they work.

    Many washers drain into laundry sinks in basements.

    But you have options to correct that rube.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • azward
    azward Member Posts: 53

    This is the existing washing machine drain in the basement. The drain hose is tucked into a 2" stand pipe.

    The existing PVC pipe inside the vanity is a standard 1.5". The steel pipe that it ties to looks also like 1.5". Due to the concerns on overflow, the planned washer drain inside the vanity cannot use a standpipe. Question is how to connect the corrugated drain hose to the planned T via a control valve as you mentioned?

    Years ago, I used to manually drain the washer into the sink or bathtub each time. What I'm looking for is probably a semi permanent solution.

    IMG20260207171428.jpg
  • mattmia2
    mattmia2 Member Posts: 16,462

    i believe the manufacturer of the washer says it has to drain in to a laundry tub or standpipe, it can not directly connect to the drain pipe.

    Intplm.
  • azward
    azward Member Posts: 53
    edited February 8

    the wye cut into the pvc pipe.. can it be hub x spigot? So spigot end should use a fernco coupling to join to the PVC pipe?

    When the washer drain brings into the other hub, it naturally forms a wet vent for the shower drain?

    image.png
    Intplm.
  • azward
    azward Member Posts: 53

    The next question would be how to break the siphon on the washer drain, so that the shower water is not siphoned into the washer.

    I don't understand why the air break kit could be installed there.. the water will not be pumped out of that vent?

    image.png
  • mattmia2
    mattmia2 Member Posts: 16,462

    the siphon break is a vacuum breaker, it is a check valve that only lets air in, it doesn't let air or water out.

    azward
  • azward
    azward Member Posts: 53

    A relevant question is, need to drill about 1 1/2" hole through the wall. After renovation, the outer part of wall is still plaster wall, made by stacking up horizontal wood strips, with plaster spread between layers, and a plaster finish covering on the outside.

    Does anyone have experience drilling through this type of wall?

    IMG20250723192500.jpg IMG20250723192349.jpg
  • mattmia2
    mattmia2 Member Posts: 16,462

    a screwdriver and oscillating tool is probably the best way to cut through plaster on wood lath. use an old screwdriver and hammer to tap the outline of the hole you need somewhat gently and break out the plaster then use the oscillating tool to cut the lath. if you do it too violently you'll break the part of the plaster that is keyed between the lath and then the plaster will come loose. if you use a different type of saw to cut the lath it is best to cut almost all the way through one side then cut through the other side then cut the last of the first side. that keeps the saw from grabbing the lath and shaking it around when you cut the second side.

    azward
  • azward
    azward Member Posts: 53

    I will check if the washer already has a built-in air break, in that case I wouldn't add a second one

  • hot_rod
    hot_rod Member Posts: 27,329

    A carbide or diamond hole saw works for the plaster, also for wood if you go slowly. Dirt cheap at Harbor Frieght.

    Screenshot 2026-02-08 at 3.36.47 PM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • hot_rod
    hot_rod Member Posts: 27,329

    Here is an option.

    Cut a 2" combo into the shower trap arm. turn up into the wall, then about 8" above the floor a 2 X 1-1/2 san tee.

    2" facing out for the washer trap, 1-1/2" up, tie into the 1-1/2' horizontal circuit ventcircuit vent

    Technically the vertical should increase 1 size when you wet vent, but this would work fine for a washer drain.

    Now you vent your shower properly and have a 2" washer drain. Without messing with the CI soil pipe.

    It could be two stud spaces to the right, 1st pic, if that helps. Cut off the last right ell on the horizontal 1-1/2 vent couple the new pvc vent on there. Then remove piping below to the tee in the floor. A Fernco cap on the 1-1/2 where you cut it.

    Looks like that was an old tub drain and vent?

    Screenshot 2026-02-08 at 5.06.55 PM.png Screenshot 2026-02-08 at 4.49.59 PM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Intplm.
  • azward
    azward Member Posts: 53
    edited February 9

    Yes, the end stub of the L is the original shower drain.

    Why does the number of stud spaces matter?

    Access to where the wall joins the floor might be difficult. Using a rubber hose may overcome this difficulty. Is a type a1 hose up to standards?

  • Intplm.
    Intplm. Member Posts: 2,994

    No…do not pipe it like that. Too much chance of drain issues with the toilet and the high velocity discharge from the washing machine.

    I believe the original post does not want to demo the new bathroom.

    The washing machine. Where is it going to be placed if not in the newly renovated bathroom? Next is where I mentioned above on where to discharge the unit. That would be the cast iron stack pictured above.

  • Grallert
    Grallert Member Posts: 1,105

    I can't imagine that the copper is connecting to steel. More likely threaded brass. I could be wrong

    Miss Hall's School service mechanic, greenhouse manager, teacher, dog walker and designated driver

  • mattmia2
    mattmia2 Member Posts: 16,462

    around here there is still lots of galvanized supply around.

    Grallert
  • pecmsg
    pecmsg Member Posts: 7,024

    I believe the OP has already closed in the walls and floor!

    Intplm.
  • azward
    azward Member Posts: 53

    it's a pipe to sweat cup adapter, right?

    so threaded copper does exist. probably only in an adapter to other materials.

    image.png
  • azward
    azward Member Posts: 53
    edited February 9

    it's planned in the bedroom right behind the wall

    there's some hope to do the cutting from the lower floor ceiling.. in that way in the bathroom i only need to open part of the USG DUROCK cement board (11 posts earlier).. but access is still challenge which is why i asked if reinforced rubber hose can be used to substitute pvc

  • Intplm.
    Intplm. Member Posts: 2,994

    Rubber re-enforced hose for a sewage drain is not recommended. Only the hose supplied by the manufacturer as a drain to a properly installed house drain meant to receive the discharge of a washing machine. You seem to be looking for short cuts. There are none here. You need to do this properly.

    mattmia2
  • Grallert
    Grallert Member Posts: 1,105
    edited February 9

    I personally have never run across threaded copper plumbing of any kind I have run across threaded brass. I misspoke when I said of any kind. Of course I've seen used and adaptors But never tees elbows nipples etc.

    Miss Hall's School service mechanic, greenhouse manager, teacher, dog walker and designated driver

  • Larry Weingarten
    Larry Weingarten Member Posts: 4,067

    Hi @Grallert , I was just going from the somewhat fuzzy picture of the piping early in this thread, but it looks just like galvanized steel transitioning to copper via a copper female adapter, as pictured above. I've seen people do this around here, and it always either leaks or plugs up with rust. If it were exposed and accessible, maybe it could be left alone for a bit. But being inside of a wall is a guarantee of problems that will be unpleasant to fix. 😈

    Yours, Larry