What is this strange valve/trap from my boiler to condensate pump?
Actually, that cast iron piece is called an &quot;air gap&quot; which is used so contaminated water of a sewer pipe or drain  will never be drawn up that discharge pipe to contaminate anything above. This is usually how  water cooler is drained so the discharge of water to the drain or sewer discharge pipe could never cause a negative pressure on the drain and pull water up onto the water cooler surface. Google the words &quot;air gap&quot;