Why do I get terrible static in my phone mic / recording when my phone is charging from the mains?
From what you have described it sounds like your phone charger is carrying a lot of noise from the mains to your phone.


Noise on your power source can come from a variety of causes, for example the one you have listed in your question: a washing machine. Electro-mechanical systems that take a lot of power are difficult to regulate, and can thus push noise back on to the mains voltage.
AC-DC converters then typically try to remove this noise in the form of filtering, but some are made better than others.
Again, your phone will probably be filtering the DC that is supplied, but in this case it sounds as though it is not filtering it sufficiently and is actually letting it effect other subcircuits, in this case your microphone circuit. Microphones (I'm presuming an analogue mic) are very sensitive to noise as the signal they produce are very low amplitude.


When you are just on your battery the noise will not be present as batteries are generally very quiet power supplies.

The noise shouldn't be damaging, but if you are very concerned there are additional filters you can get in the form of power strips that could reduce this issue.