I am trying to install a new washing machine, but I found that the sink drain pipe is closed. Please see the pictures below.

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My questions:

  • Should I cut the top of this plastic or is there a component I need to buy?
  • Is it something that I will need to ask permission for from the house manager?
  • Where's the trap in this jungle of piping?! Jul 5 '18 at 11:37
  • 2
    @ThreePhaseEel It's there. Think through the water flow. Starting at the top it goes right, down, left, UP (ie: trap), then 45 down left into the flex hose. Remember a trap doesn't have to be curved, it just has to have a point where the water goes down and up again. Jul 5 '18 at 12:59
  • @TheEvilGreebo -- I was thinking the flex hose was another inlet, with water going out to the right. :P Jul 5 '18 at 23:17

And for a clothes washer...

Based on comments, this is apparently really a clothes washer rather than a dishwasher.

  1. It varies a bit depending on the particular machine, but a clothes washer typically uses more water than a dishwasher, and therefore drains a LOT more at one time. A quick search found 6 gallons for a typical dishwasher and 15 - 30 gallons for a high-efficiency clothes washer. YMMV, but both machines have wash & rinse cycles, so that indicates somewhere between 2 and 5 times as much water being drained at one time from a clothes washer as a dishwasher. I would not count on the typical kitchen sink drainpipe being able to handle that much water. I suggest checking with the manufacturer of the washer for information/installation recommendations. Typical installations that I have seen have a rubber drain hose either into a laundry tub - which effectively buffers the water by having just enough space to hold a full machine-load of water as it drains down through the drain pipe slower than it comes out of the machine - or into a larger drain pipe. I'd be a bit uneasy about putting a clothes washer drain hose into that sink drain pipe.

  2. Lint is a big issue in general. It is even more of an issue draining into the kitchen drain pipe which will be more likely than a typical laundry room pipe to have a coating of grease. The flexible corrugated pipe makes this even worse. The solution to the lint problem is to install what we call in my house a metal meshie. There are a few varieties, metal, fabric or plastic, but the basic idea is to catch the lint in a removable/disposable mesh so that the water going down the drain is (relatively) clean of fibers that would eventually clog the pipes.

  3. Water usage is even more of an issue with a clothes washer than a dishwasher. I know of plenty of apartments (USA) that have dishwashers (which properly used can actually use LESS water than washing by hand) but have strict rules against installing clothes washers (due to water use) and dryers (due to electricity use).

  • Thanks for your reply. But now I bought it and I need to install it (the kitchen is the only option I have), Would placing the drainer over the sink helps (so the water has more time to be drained down). The machine is very small (5kg) : otto.de/p/…
    – M20
    Jul 6 '18 at 7:11
  • What is the model number? Jul 6 '18 at 12:06
  • hanseatic.de/produkte/auflistung/detail/product/296878 Sorry I could not find any information about it in English.
    – M20
    Jul 6 '18 at 12:09
  • I think I will buy a Y drainage pipe and connect it to the main drainage pipe.
    – M20
    Jul 6 '18 at 12:20
  • Drainer over the sink may be your best option. That would allow a few gallons of "output buffer" (using computer term here - not sure if that what the right term is for plumbing) so that the washer can drain safely. Jul 6 '18 at 14:14

That connection you are referencing is for an automatic dish washer not a clothes washer But to answer your question, all you need is a razor knife commonly called a box cutter, a hack saw either manual or electric, or anything that will cut plastic. Just cut off the plugged piece at the top only not close to the drain line.If, as you say, you are installing a clothes washer you will need access to a larger drain pipe so the water will not back up the drain when the washer pumps out the water.

  • To clarify, just cut the thin cap end of the barbed fitting. Leave the tapered barbs in place to hold the drain tube.
    – isherwood
    Jul 5 '18 at 16:04
  • Can I do this adaptation by myself with the need of a plumber? (For the clothing machine)
    – M20
    Jul 5 '18 at 23:33

Dishwasher Inlet

First of all, I assume we are talking here about a dishwasher and not a machine for washing clothing. It is unusual to connect a "washing machine" (as opposed to a "dishwasher") under the kitchen sink, though not impossible. I believe this is a difference in terminology between the USA and other parts of the world. Continuing based on dishwasher.

  1. In the USA, many (most?) people have a disposal under the kitchen sink. I understand that is not nearly as common in other parts of the world. Most disposals (all the ones I've worked with, but I am not a professional plumber so my experience is limited) have a dishwasher inlet that looks very similar to the capped pipe. I believe the capped pipe is a dishwasher inlet. You should be able to remove (cut off if necessary, as close to the top as possible) the cap and attach the dishwasher hose directly to the pipe. The ridges on the pipe help to keep the dishwasher hose attached, though you can put on a clamp if it does not seem to be secure enough. If the dishwasher hose and the pipe are not compatible (the dishwasher hose should be just large enough to fit snugly over the pipe) then you will need an adapter - measure the hose and the pipe and go to your favorite hardware store.

  2. When you install the dishwasher hose, it can be connected in one of two ways:

    • Air gap - a metal/plastic gadget that is typically installed next to the faucet. One hose goes from the dishwasher to the air gap. Another hose goes from the air gap down to the pipes. These are a pain (they often break over time, leaking around & under the sink) but in some places they are still the only legal way to install a dishwasher.
    • High hose loop - the dishwasher hose loops up to just under the counter and then down to the pipes. This has the same general effect as a traditional air gap - preventing sewer water from backing up into the dishwasher - but is much simpler and easier to install.
  3. As far as asking permission: If the landlord already knows you are installing a dishwasher then there should not be an issue. If the landlord does NOT know you are installing a dishwasher, then I recommend checking with him first. Cutting the cap off the pipe is no big deal, but installing a dishwasher - which can affect water usage and which (typically, unless you are using a portable unit, in which case cutting the pipes would not even be an issue) normally involves replacing a cabinet with the dishwasher - is something the landlord would expect to be consulted before installation.

  4. While you're at it, the pipes look a bit strange. As already noted in comments, the trap is not a typical P-trap, though logically it should work. In addition, the pipe coming out of the trap is a flexible corrugated hose. That is generally not recommended as it can collect grease & debris in the folds and clog more easily than a regular pipe. (You may say "but isn't the dishwasher hose the same?" and the answer is "the dishwasher doesn't get as much as the main drain pipe and the dishwasher hose is easily removable to clean if it gets clogged".)

  • No we are talking about a washing machine.
    – M20
    Jul 5 '18 at 23:22
  • A clothes washer in the kitchen next to the sink? In that case, a different set of issues come into play. The biggest is LINT. Jul 5 '18 at 23:32
  • It is not directly next to the sink, there is small separation between them. I had the same set up in my old flat.
    – M20
    Jul 5 '18 at 23:35

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