The figures on this page are indicative ranges based on typical Belfast and Northern Ireland pricing. Every installer quotes independently, and the exact figure depends on your system, access and the amount of sludge. Use these numbers as a sense-check, not a fixed price.
Typical Belfast pricing
A power flush on a straightforward domestic system with up to 8 radiators typically falls in the £500–£700 range. Most quotes include the chemical dose, a fresh inhibitor after flushing, a written before/after report and a warranty certificate.
Systems with 9–12 radiators more commonly run £700–£900. Larger properties, systems with suspected pump or heat exchanger issues, or badly neglected black-water systems are quoted case-by-case after a site visit.
Where a flush is bundled with a new boiler installation (often a manufacturer warranty requirement), installers typically discount the flush because they're already on site and set up. Expect the bundled price to be £100–£200 less than a standalone flush.
What moves the price
- 01 System size, more radiators mean more water, more time and more chemical.
- 02 Sludge severity, lightly dirty systems flush faster than black-water systems.
- 03 Access to the boiler, tight cupboards and awkward pipework add time.
- 04 Whether a new pump, magnetic filter or fresh inhibitor is needed on the day.
- 05 Whether the flush is bundled with a new boiler install (typically cheaper as a combined job).
When a flush isn't the answer
Cold radiators aren't always a sludge problem. A failed pump, a stuck motorised valve, or a poorly balanced system can cause the same symptoms for a fraction of the cost to fix. A good installer will run a short diagnostic first rather than flushing blind.
Diagnostic call-outs across Belfast typically cost £95–£150, and that cost is often deducted from any subsequent work. Spending £100 to find the real cause is better than £600 on the wrong fix.
Equally, if a boiler is 15+ years old and already struggling, a new installation usually makes more sense than flushing a system that's close to end-of-life. A reputable installer will say so, rather than quote a flush on a system they know is about to be replaced.
What a proper quote should include
A credible power flush quote breaks down into clear line items:
- Chemical flush agent and disposal.
- Fresh corrosion inhibitor on refill.
- Magnetic filter check or replacement where fitted.
- Written before/after readings on each radiator.
- A warranty or workmanship certificate.
Quotes that just list a flat "day rate" with no itemised breakdown are worth pushing back on — a proper flush is about what comes out of the system, not just time on site.