Ej: Sub-nucleate boiling occurs on electric WH elements. When bubbles break off the element and collapse noise is generated.
Agreed, but it would very difficult to say which element the noise was coming from if not impossible much less the squeaking.
If both your washers supply hoses have hot water coming out of them then most likely there is a cross over at some point. A good place to start would be with single lever faucets that mix both hot and cold.