This type of coupling relies on a rubber 'cone' washer that clamps onto the thing (called a spigot) that you've pulled out.
If you're relying on sealant with this type of coupling then you're doing it all wrong.
You need to unscrew the white nut, put it onto the spigot in preparation, then remove the parts inside the trap, then place them around the spigot, then push the whole caboodle back into the trap and do up the white nut.
If the rubbber washer looks worn, compressed, twisted or otherwise not serviceable, then you can buy a replacement washer, or, if you can't find such a thing in a hurry, then buy a multifit fitting and steal the washer from that.
leak where washing machine waste joins U bend.
it sounds like the rubber washer didnt come out with the spigot so it could be stuck in the pipe, i cant actually get into a position where i can see into the pipe because of the position of the joint in relation to the wall / cupboards.
The rubber i used as a temp. fix wasnt sealant it was literally just a thin piece of rubber so i can remove quite easily.
Whatever is needed to make it watertight must have been there before beacuse it was perfect before i messed with it
Thanks for the reply
What had happened is that the nut wasn't tightened enough (or became loose), then you pulled out the spigot, and when pushing it in again you've unwittingly pushed the rubber washer into the trap.
I recommend that you take the trap off (with a bowl underneath) to retrieve the old washer, because you shouldn't let it go down the drain and you shouldn't leave it in the trap to cause a blockage.
cheers softus that sounds like the most logical explanation, i will have a bash at it tonight.
no sign of the washer in the trap, it must have gone down the drain however i got a 90 degree joint for a couple of quid from B&Q so i could use a washer of it as you suggested and it is all back to normal now.