Washing Machine Waste

[Readingplumber]

Hi,

What is the reason that the washing maching waste pipe when it comes out of the trap has to(loop) higher than the sink waste?

I always thought it was to stop kitchen sink water draining into the machine, but on googling this it says to stop the washing machine waste being syphoned out?

Also if installing a washing machine waste into a seperate stack pipe does the waste from the machine have to be pinned up in the air or can it be slanted straight downwards?

Thanks

 

[Readingplumber]

Hi Thanks,

What is the reason for that?

 

[davetheplumber]

it creates a trap in the bottom of the machine stopping smells etc coming back