Hi John,
Your thinking of an internal bypass, I would't reccomend one on any machine but hey...
The water doesn't actually get more and more compressed thats why it bypasses to stop that, if it didn't it would do damage like this. In this example the valve capmthreads gave way, and noone was injured, it can actually fire the caps off and bury them in the ceiling or someones head!

The reason it gets hot is because the pump must always pump water and when underloader goes into bypass the bypass water goes round from outlet back to the inlet, therefore no fresh colder water is introduced into this short circuit after a few mins of running like this the small quantity of water keeps picking up the heat the pump is generating. A bit like running car engine with the radiator removed from the circuit
In an extenal or back to tank bypass the pump will have to heat the whole tank up to do any damage, that would take forever.
Of course the bypass could just vent onto the floor but that would waste water.