Existing pipework can often be reused

In many retrofit installations, the existing heating pipework can remain in place.

Modern central heating systems typically use pipe diameters that are suitable for heat pump flow rates.

However, the final decision depends on system design and heating demand.

Flow rates are important

Heat pumps operate with lower temperature water compared with gas boilers.

To deliver the same amount of heat, systems often rely on higher water flow rates.

Pipework must therefore allow sufficient circulation without excessive resistance.

When pipe upgrades may be needed

In some older systems, pipework may be smaller or arranged in ways that limit flow.

• Very old microbore pipe systems
• Poorly balanced heating circuits
• Complex pipe layouts

In these cases, certain sections of pipework may be upgraded to improve performance.

Radiators are often more important than pipework

In many retrofit installations, radiator sizing has a bigger impact on system performance than pipework itself.

Heat pumps operate most efficiently with larger radiators or underfloor heating systems that can deliver heat at lower temperatures.

Why system design matters

Professional installers usually perform room-by-room heat loss calculations before designing a heat pump system.

These calculations help determine:

• Heat pump size
• Radiator sizing
• Required water flow rates
• Pipework suitability

Key takeaway