If you have been using your Keurig brewer for a while, you may have experienced a problem with a build-up of scale within the narrow tubes in the brewer. This is particularly prone to happen in areas with hard water.
Fortunately, the display screen on the brewer will tell you when it is time to descale.
You can descale your brewer either by running vinegar through the brewer, and then rinsing with a few cycles of water, or with a product called Dezcal.
But what if you do all this, but you still have a problem? Some people descale their brewers and find the descale message remains, or they are still not getting a full cup of water coming through when they brew.
The answer is very simple, and has been the subject of a discussion over on the CoffeeDetective.com website.
Sometimes coffee grinds from the K-Cup back up into the steel needle that pierces the top of the K-Cup. If the needle becomes clogged, then it gets harder for water to pass through when you are brewing.
Simply take a toothpick or paperclip and gently scrape away any build-up of coffee grinds in the needle. Then run water through the system to flush out the loose grinds. Be careful when you do this, as the needle is very sharp.
Anyway, this seems to do the trick.