The blue wax mixing valve is front and center. As it sits it receives hot water (165) from boiler on the left and mixes it with incoming (80) pool water on the right to send tempered water down to the pump and into the boiler.

It’s purpose is to reduce condensation in the boiler combustion chamber..

Point is it’s all 2 1/2 and is the mixing valve is supplied by the seller of these “systems”...

If you follow the pipe going away from the right side you can see back where it reduces down from 4 to 2 1/2, so in regards to increasing suction side.. it technically could be done. But I’m not convinced that would accomplish anything?
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She never made it past the bedroom door, what was she aiming for...?
She's gone shootin..