I had some new plumbing added to a cloakroom/utility room for the washing machine. I have about 18 inches of waste pipe coming out of the floor (connected straight onto a boss in the soil-pipe under the floor). What type of trap do I need before adding the washing machine spigot?
https://www.screwfix.com/p/floplast-wc11-universal-compression-waste-bend-90-40mm/35203 OR https://www.screwfix.com/p/floplast-push-fit-waste-knuckle-bend-white-90-40mm/18679
Cut the pipe a bit closer to the floor and fit S Trap with an upstand pipe for the machine drain hose.
Just source a S-trap with 40mm compression fittings on both connections but why make more work when purpose made wm/dw stand pipe kits are available and are known to work using the correct fittings has advantages
I'm all for using the correct fitting, but I just don't know what that is! The stand-pipe kit has a horizontal connecition and I have a vertical pipe. Do I just add a 90 degree elbow to the pipe and then connect it to the stand-pipe? This will effectively form an s-trap anyway. Are s-traps bad? I keep seeing info on US websites suggesting that are the wrong thing to use.
Seriosuly though, the suggestion seems to be that they can allow the trap to be siphoned empty? Not sure why. if I fit the standpipe, can I attach a washing machine spigot at the top (like the one under my sink)? Or would this cause a venting problem?
Only if the vertical is too low, the pipe to the drain hasn`t the correct "Fall" on it or has a restriction in it.
It also should only go into the standpipe a short distance of I would say approx 6” (150mm) To push it in too far can cause a syphon effect on machine. Best way to achieve keeping the hose correct distance is to use the U shaped plastic former that the waste hose snaps into