Most of the time it’s just air bubbles – not dangerous and your cloudy hot water is nothing to worry about.
Usually cloudy hot water is caused by air getting into your hot water pipework. This can happen when you have fitted new hardware such as a tap or hot water system. This will normally right itself as air purges from your system. Another explanation could be from pressure changes when cold water enters your system. You have nothing to worry about if a newly poured glass of hot water appears cloudy but settles within a few minutes (this is when the tiny air bubbles dissipate).
However, if the water remains cloudy once it has cooled, you may have problems elsewhere. If so, give Arrow Plumbing & Gas a call… we’ll sort out your cloudy hot water quick-as-a-flush!