You've probably just got some slimey build up in the u bend under the sink. Try taking it off & giving it a good scrub with some bleach. Mine 'burps' every time the washing machine or dishwasher is on so i think that is normal!
K & A recomend you to put a handful of washing soda crystals and then a kettleful of boiling water..this will keep your draind running clear..do this about once a month.....
Get yourself a bottle of sink and plughole unblocker, go to Wilkos and dont wast your money on brand names, the stuff I use is 99p a bottle and is brill I used it on the bath because its so hard to get at the drain to unblock it, I waas so plesed with the result I now keep a few bottles under the sink just in case, I also used it on the kitchen sink because it smelt like the dogs breth it worked a treat.
Another thing you could try is a cup of bicarb followed by a cup of white vinegar, leave for a couple of hours and flush through with hot water. Add the vinegar slowly as it fizzes up.
That's what I was going to suggest Mad Rat. I'm having to do my bath and shower plugholes on a regular basis. I'm taking drugs that is making my hair fall out and the plugholes are filling up with hair Having hair cropped tomorrow - hope it doesn't reveal any bald patches
it worked a treat.
