sink not draining but pipes clear??? All aspects of plumbing questions and answers, help, tips and information

[asacity]

Hi,
we have an issue with our en-suite basin which we cannot fathom! it was originally blocked in the waste pipe (toothpaste) but we have now cleared that, and if we put water directly into the waste pipe via a jug it drains away perfectly. When we connect the sink trap back to it and fill the sink, it doesn't drain any further than the trap???? we have done this with hot water and can trace exactly where the water gets to....no higher than the trap! We have tried different traps - now have a S type, but still no different. Is there some basic plumbing vacuum/gravity that we have missed????
Please help, its driving me crackers!

[fulfordroofing]

hi it sounds like you have an air lock in the trap very common problem there should be a small screw cap on the trap fill the basin place a bowl under the trap un screw the cap and remove the plug then re screw the cap