Low Loss Headers and Hydraulic Separation
A low loss header separates the boiler's own flow requirement from the system's.
A low loss header separates the boiler's own flow requirement from the system's. On larger or heavily zoned systems it stops the boiler and the circuits fighting each other for flow.
The problem it solves
When zones close, flow through the boiler collapses. A header keeps the boiler's primary circuit stable regardless of what the zones are doing.
Sizing and connection order
Get the connections or the velocities wrong and you get mixing, which drops return temperatures unpredictably and hurts condensing performance.
Where it is overkill
A single-zone domestic system with a modern modulating boiler usually does not need one. Fitting one anyway adds cost and a mixing risk.
Questions we get asked
Is a low loss header the same as a buffer?
No. A header separates flow; a buffer stores volume. They solve different problems and are sometimes both required.
Will it reduce efficiency?
Badly sized, yes, through mixing. Correctly sized, it protects both the boiler and the circuits.
Do I need one for a heat pump?
Heat pump systems often need volume and separation, but the design should decide, not habit.