When was the last time you had the milk leaking between the plastic ring and bottle? You are wondering why sometimes it leaks, and at times it doesn't. Twisting it tightly or loosening it doesn't help. You have searched Avent website, and asked around 'is there a special way' in using Avent feeding bottle, other than putting the nipple, plastic ring and bottle together. Well, I think I have the answer for you.
When I first started feeding my son, I had the same exact problem. It left me in confusion as to why it leaks sometimes. Instead of feeling frustrated, the 'mysterious' leak got me really curious.
The Avent bottle nipple has three air valves near the base of the nipple. As we all know the valve lets air into the bottle to prevent any vacuum build-up.Alright, now take a look at the plastic ring. If you look closely, there are four sets of fins around the plastic ring.
Now you just need to place and align the nipple with at least two of the air valves within the fins before putting it together. Voila! That's it no more leaks!
Take note, if you twist it too tight the valves won't work properly and therefore creating a vacuum in the bottle and milk won't flow out that easily. I can't tell you how tight is tight enough for you, so some trial and error is needed. Or you might want to checkout my method here. I'd like to add that over tightening it will affect the alignment ( credits and thanks to 'adhis' for her tip ).
Despite this, my wife and I still use Avent bottles and in fact we've bought over 18 bottles to date and still using it for our little baby girl. Avent feeding bottles is still one the best bottles around.
So I hope this little trick helped you, and happy feeding! :)
*Update: 27 Nov 2008
Here are some new photos I took today. Added some descriptions as well ( click on the photos for a bigger version ).
ps. I have seen some sites and blogs posting up my method, I'd appreciate it if you give credit where it's due, that's all I ask =).
*Update: 08 October 2009
Avent has started selling a newer version of the Avent BPA free bottles more than a month ago. This new bottle has an extra blue/white ring and it's anti-colic system is a two piece system ( instead of one-piece originally ). People who bought these did not experience any leaks. Checkout the 9oz dual pack on Amazon.com.