Drainage scheme for washing machine in garage.

[pete m]

I wonder if I can get some advice on a washing machine drainage layout?
I plan to install the machine in an outside garage. The difficulty will be arranging a drainage scheme to a near-by open grill drain outside the kitchen.
Waste pipe was planned to be 40mm, but I understand 50mm is recommended for modern machines.

The 1000mm section, effectively 40 / 50mm below ground would form a trap (rather a long one). The proposed arrangement is to not have a pipe blocking the walkway between house and garage.

Thanks for reading this – Pete.

 

[AC Power]

If it were myself doing this, without hiring a plumber, I would do what your thinking of:

And of course, if your in sub-zero temperatures, you'll have to install heat trace around that drain. Stick with the 50mm (2"). Some of the newer washers discharge quite a bit of water, and quickly at that! I am not sure you even need a trap here as your diagram shows the water dumping into a drain....the drain will have it's own P-trap already. If your drain didn't have a trap, you'd be getting pungent sewer odors emanating from it.

 

[pete m]

Many thanks for your quick reply.

I viewed the 1000mm section as a trap as it would most likely be always full of water.
If it syphoned out during the machine drain cycle it would certainly solve the possible freezing-up issue!

The drain its going into has indeed got a trap.
Thanks again for taking the time to reply

Pete

 

[AC Power]

The P-trap will only syphon when downstream water rushes by the washing machines point-of-attachment to the drain. In other words, your drawing seems to indicate your simply dumping the washing machine's drain water into an open floor drain. You might get syphon effect if you dumped a lot of water directly into the floor drain at a rate that it is "suffocated" with water.....under those circumstances, you would create a vacuum, thereby possible emptying the trap. You washing machine itself won't empty the trap.

 

[piglet11]

Burying waste pipe that is designed to be used above ground is not a great idea.
Nor is having a long trap underground a good idea.
I don't think I would worry too much about 2" instead of 1.5" as the latter has been used for large volumes like baths and kitchen sink wastes for years, but under the circumstances, it might be wise to use the larger size.
The bit that worries me is burying the pipe.
I think I would run the waste pipe in a duct, maybe 68-mm downpipe or 82-mm soil.
Use slow bends and maybe accommodate at least one access point for rodding.
Water regs specify supply pipe depth as 75-cm minimum to avoid freezing.
Good practice for pipe burial would include a gravel pack and a marker tape.
I once found a 4" yellow HDPE being used as a soakaway pipe.
HDPE is widely used for underground use, very tough, and much better than PVC and ABS for surviving the odd fork.

 

[pete m]

Thanks piglet11 - useful info.
Thanks AC Power for your follow up comments.

The eventual pipe route was thus:

I tried many rinse / drain cycles, and all functioned as intended.
I lagged the 50mm pipe (all solvent weld) from X to Y & put 25mm polystyrene underneath. Moveable paving labs cover that section so I can keep an eye on what's going if needed.

 

[AC Power]

I'm Happy for You.....Great!