Difference b/t One-Way Check Valve and Tractor protection valve

Yes, you did make it difficult!

The compressor creates pressure which flows to your air tanks( reservoir). The check valve allows pressure into the tanks, but is closed by the developed pressure in the tank, preventing loss of compressed air back to the source.

That covers part one

 

tractor pro. valve is at rear of truck to keep air from leakn down if trailer air line leak.

 

The TPV prevents high volume air loss from the trailer. It is supplied air by the red knob on the dash.

I guess the short answer is, the one way is active all the time at the source of air compression - the TPV is activated by massive loss from the trailer.

Hope that helps? Comments, anyone?

 

Sounds correct to me! Yep, the tractor protection valve (TPV) is kinda a "balanced" valve and stays in normal position when the tractor air and trailer outlet air are stable, no matter if air pressure is 70 psi or 125 psi. However, when a sudden air loss is detected (say, a broken or disconnected air hose to the gladhand) it senses that the trailer side is quickly loosing air, at which point the TPV will "flip" to the closed position to protect air loss from the tractor itself.

The 1-way check valve between the compressor and tank would only prevent a leak before the check valve, which is the compressor. (correct)
It is mainly there (in the tank fitting or line) as a "one direction" valve to let air go from the compressor to the tank, but not from the tank to the compressor.
Without a 1-way valve (check valve) it would keep tank pressure (up to ~125 psi) on the compressor outlet head at all times, and thus make compressor work harder.
If a leak occurs after the check valve (tank side) it has no effect on the check valve. The check valve is not an issue at all, in this scenario.

blairandgretchen's info is nicely worded & "spot on".
All replies are saying the same thing, just each one of us rewording it... to make you even more confused.