Kettle making a loud popping sound for a while

[Rollerball]

I have a Morphy Richards jug kettle, it's about 2 years old.

One of these:

http://www.morphyrichards.co.uk/products/kettles/jug-kettles/43905-Accents-Jug-Kettle-Black.html

As of today it's started to make a fairly vigorous popping sound in the early heating stages - as the water heats up the popping sound disappears.

Is this indicative of a problem? Is the element about to burn out or explode?

The only 'change' in its use that I can think of is that yesterday my water supply was off for a number of hours so I had to resort to using bottled (still) water in the kettle. Would this have made a difference?

Today, whether I use bottled or tap water, the popping sound is still present.

Thanks

 

[DetlefSchmitz]

It's caused by an effect called cavitation. If so nothing to worry about, but might be time to de-scale your kettle.

 

[Rollerball]

Many thanks.