Twang

[Big G]

I too have had these twangs.....all be it depending what type of beer I brew. Since I have started treating my water these have all disapeared.

[coatesg]

Soda crystals are good for cleaning, but you'll probably need to use a sanitiser too. You could blitz the entire keg (dismantling the tap, lid, etc) with thin bleach and rinse thoroughly. The cheapo Sainburys thin unscented bleach at 30p or whatever for 2l is perfect. Or something like VWP will do the same.