Dishwasher, washer-dryer, no air gap, and flooding! (long...sorry!)
Posted by Roscoe on May 25, 2003 at 20:52:08:
Hopefully I can get some good advice here -- searched the site and didn't quite find an answer to my newly occurring problem. I'm gonna call my plumber soon but figured I'd post first, just to see if I can solve this myself. This post is really long because I want to explain everything clearly and thoroughly.

I'm in a condo, efficiency kitchen, with very little room to spare. My kitchen sink is really just a large bar sink (14" x 16"), and it mounts through a granite countertop into a non-standard sink basin cabinet (non-standard because it's only 18" wide -- it's actually just a regular cabinet that I'm using as a sink basin). On one side of the sink, under the granite countertop, is an 18" dishwasher (which I very rarely use -- maybe 2 times per year, just to run it). On the other side of the sink, under the granite counter, is an Equator combo washer/dryer (ventless, single box, runs on 110V). All of this stuff hooks in below my sink, along with a garbage disposal and refrigerator ice dispenser water line. So, it's REALLY crowded under there, and I have basically no room to maneuver.

I have no air gap. Instead, when my plumber installed the dishwasher, he just looped the drain hose pretty high under the sink basin, so it's almost as high as the top of the sink. I assume this is fine (right??).

My problem is, how do I drain the Equator washer/dryer? Can I drain this just like I drain the diswasher, into the same 7/8" intake line that's built into the garbage disposal, taking care to loop the washer/dryer drain line high under the sink basin? [The inside diameter of the Equator's flexible gray drain hose is 7/8", which I think is the same as the dishwasher's drain hose.]

Here's the deal. When I did all the remodeling about 3 years ago, I jury-rigged a standpipe under the sink that connected, via a 1.5" PVC "T", to the garbage disposal's drain line. In other words, the middle of this "T" connected to the garbage disposal drain, the bottom of the "T" goes to the sink trap/sewer drain, and the top of the "T" was connected to a makeshift standpipe that I was barely able to sneak up the inside wall of the undersink cabinet, almost to the top of the sink (standpipe was about 33" from the floor). The gray rubber/plastic Equator drain hose rested just inside the top of this standpipe. [Hopefully all of this makes sense].

This seemed to work fine for the past 2 years or so -- no flooding or leaks or anything -- even though I had always been concerned that the directional PVC "T" that connected the Equator washer/dryer to the disposal drain and sink trap/sewer wouldn't allow enough of the washer/dryer water to flow. This is because the directional downspout -- the PVC shape inside the "T" that makes it directional, by "pointing" the disposal/sink waste water downwards and letting the Equator wastewater flow in from above -- takes up a bunch of room inside the pipe (of course). This partially blocks the inside of the 1.5" PVC pipe and doesn't seem like should let all the Equator wastewater to drain at the proper rate. In fact, I still don't really understand why this ever worked without flooding, because when the Equator drains, the water comes out of that hose with tremendous force. But for whatever reason, it DID work.

Recently, I've had a problem. Now, for some reason, whenever the Equator washer/dryer tries to drain, water gushes out the top of the standpipe and floods the entire undersink cabinet. Since it used to work fine, I thought there must be a blockage somewhere, so I took off the entire standpipe assembly and inspected it -- all clear, although there was some gray crap near the bottom part of it (very little, though -- just enough to coat the inside of the PVC pipe). There were are few globs nasty crud/food waste that built up around the top and sides of the directional downspout inside the PVC "T" connector, but I don't THINK there was enough of this stuff to block the flow too much. [Just for kicks, I also undid the little PVC screw cap at the very bottom of the undersink trap, to see if the trap was clogged. I didn't think was the problem, since the sink drained fine, and indeed the trap was all clear when I stuck my finger up in there.] Since the only obstruction I could find was the few globs of crap that accumulated around the directional downspout (inside the "T" connector), I ASSUME this caused the problem -- maybe there was just barely enough clearance inside this connector to prevent a flood in the first place, and those globs caused just enough of an additional occlusion to flood the standpipe.

I never liked that directional "T" connector in the first place, but it's what the plumbing supply store guy told me to use. I just don't understand what good it does, for my purposes. I COULD just replace it with a regular, non-direction, PVC "T" connector and see if that works. However, this means I'd also have to reinstall the whole standpipe assembly, which is a MAJOR pain and which I'd like to avoid if possible.

So here's what I was thinking:

(1) Get rid of the directional PVC "T" and replace it with a normal PVC elbow, so the garbage disposal drains into the undersink trap like it typically should.

(2) Get rid of the standpipe and attach the Equator drain hose directly to the garbage disposal's dishwasher input. Of course, the dishwasher still needs to drain there too. I guess I'd connect both drain hoses to the garbage disposal's dishwasher input by buying some sort of 7/8" (inner diameter) PVC adapter (like a "Y"-shape, to avoid right angles -- hopefully such a thing is readily available). So, this would allow me to connect both the dishwasher AND Equator drain hoses to it.

(3) Remember that I have no air gap, so I'd need to make sure both the dishwasher and Equator drain hoses loop as close to the top of the undersink cabinet as possible (i.e., as high as possible). That's all I need to worry about, right? [Note that I don't fully understand the concept of the air gap enough to know how high it needs to be, how it really functions, etc.]

(4) I'd want to ensure that no wastewater from the sink or 1 of the 2 appliances (dishwasher, Equator) can back up into the other appliance. I assume the only way to do this would be to have 1-way check valves on each appliance's drain hose, ideally as close as possible to the disposal's dishwasher input. 1 of these check valves would be inline with the dishwasher's drain hose, and the other would be inline with the Equator's drain hose. I don't think the Equator has a built-in 1-way valve. The dishwasher, an 18" Frigidaire MRD251RHR, supposedly does have a built-in check valve. However, this check valve is inside the dishwasher rather than at the far end of the drain hose, which doesn't seem ideal (you wouldn't want random wastewater, especially under pressure, sitting in the hose, right?). So can I get small, in-line, 1-way check valves that'd still give me about the full 7/8" of inside clearance for the dishwasher and Equator wastewater to flow freely and forcefully? I assume such things exist. Is the check-valve thing a good idea, or is it totally unnecessary overkill? [Basically, what I think would be ideal, would be a 7/8" "Y"-shaped device with 1-way check valves on both forks of the "Y," to prevent backflow into these forks.]

Would this work? What would I need to be careful about? Thoughts, comments, creative ideas, etc.? Being as specific as possible would really help!! Again, my main concerns are: (1) ensuring adequate, free-flowing drainage, (2) preventing flooding under the sink, and(3) preventing wastewater from backing up into any of the appliances. Also, VERY important: nothing I do can take up much space, because there's so little room in the undersink basin, and I REALLY don't want to have to detach the garbage disposal and other stuff to finish this job (there's essentially zero room to maneuver under there).