Washing machine hose below floor level

[choco777]

Hi everyone,

I re-arranging my kitchen and would like to install the washing machine with the following setup. I will cut a trench in the concrete below the wooden floor to fit the hose.
Do you think that would work?

Thanks for your help and advice

 

[Zanne]

NO. Big fat NO.
Why?
1. The sink drain is already a code violation by creating an S-trap. The sink needs a vent.
2. The hose needs to be drained by gravity so it needs to go in to a standpipe with it's own vent and the drain it dumps in to must be at least 2" (5cm) diameter. It drains by gravity so the entrance to the standpipe needs to be higher.
3. Sink drains are of insufficient diameter to accommodate the flow of water from a washing machine- combined with no vents and the hose not being in a proper standpipe, the water isn't going to flow properly & will probably overflow & make a mess.
4. Furthermore, the water will be siphoned out of the trap so it won't form an air seal to keep sewer gases from coming back up.

Each fixture should have it's own auxiliary vent that connects with a main vent that goes out through the roof.

Just to clarify: When you say washing machine, you mean a laundry washing machine, right? Not a dishwasher?

Even with a dishwasher this would still be a "no" because of the S-trap under the sink.

 

[choco777]

Hi Zanne,

Thanks for your answer.Yes I mean a washing machine, not a dish washer.
I have now updated the setup to make it more accurate. We actually do have a sink vent (although not a roof vent). Right now here is the setup we currently have and seems to be working fine. So the new setup wouldn't be so different apart that the hose will have to travel 1m80 just below floor level.

 

[frodo]

a wye branch tail piece is 5/8'' in diameter
your washer hose is 1 1/2'' in diameter,

your idea will not work for a clothes washing machine
you would be better off to put the hose in the sink, put a weight on it to keep it from flying around


please provide a picture of the actual sink, your drawing leaves out important detail

 

[Zanne]

No problem. I think one of the experts should weigh in- but that setup is still not right. The vent needs to come AFTER the trap, not before. That sink vent is useless-- and it needs to go up and out of the house to allow sewer gases to exit the home. Otherwise, you will have a sewer gas problem- and sewer gases can make you very ill or even kill you if it builds up in large enough amounts.

Look at your drawing and tilt your head to the left. You see how the drain in black under the sink forms an S? It should go straight after the U part and then have a vent before going down. If the sink is a large utility sink, some people just secure the hose to the sink basin and let it drain. But it looks like you have a different configuration.

Here's a thread on another forum discussing the laundry & laundry tub plumbing https://www.opia.info/index.php/code-tech-database/17-fixtures/79-13-25-standpipe-to-laundry-tub but that is Canadian code, I don't know the code in London.
But the drawing would have the sink with a 90 sweep instead of a trap and it would go to the standpipe and then have a trap.


So the recommendation is to tie the sink in to the standpipe rather than tie the laundry hose in to the sink. It is also recommended to have a cleanout on the vertical pipe with the vent (somewhere above the sanitary tee- probably best to be above the flood level rim).

Caveat: I am not an expert. I have just studied plumbing but am not an actual plumber. Frodo and the others would know more so if they disagree with me, listen to them (if they weigh in).

Keep in mind that the trap arm needs to be within certain parameters: too short and it siphons, too long and the air gets blocked, which interferes with water flow.

If you absolutely can't connect to the main vent pipe, then you might be able to get away with using an Air Admittance Valve (if it is allowed in your jurisdiction) but it is not recommended. In the drawing, you would put the AAV at the top of the vent pipe. I altered your drawing, but again, one of the experts should weigh in before this is finalized.