What Happens During a Power Flush

What a power flush actually does

The problem a power flush solves is sludge, the black, magnetic build-up that forms as a heating system slowly corrodes. Over the years it settles in the bottom of radiators and in the pipework, restricting the flow of hot water so radiators go cold at the bottom, heating becomes slow to warm up, and the boiler works harder than it should.

A power flush clears that out. Unlike a gentle chemical flush that relies on the system’s own pump, a power flush uses a separate high-flow machine to circulate water and chemicals through each radiator at controlled high flow and lift the debris out. That is what makes it the more thorough clean, and why it suits systems that are genuinely full of sludge rather than just a little dirty.

That is the core of it. On a larger system we may spend more time on the radiators that are worst affected, and where there is limescale we may add a descaler. By the end, the water running out should be clear rather than black, which is the simplest sign the clean has worked. You can read more about the equipment and chemicals we use, or see what affects the price.

How long it takes and what to expect

Most power flushes take between three and six hours. A small flat with a handful of radiators is at the quicker end; a large house with ten or more radiators, or a heavily sludged system, takes longer. We will give you a realistic estimate once we have seen the system, and we confirm a clear quote for the agreed work before we begin.

On the day, someone needs to be home to give access at the start and the end, but you do not need to watch the whole thing. We protect floors and surfaces where we are working, and the dirty water is carried out through our equipment. You can read more about floor and home protection during a power flush. In most cases the heating is refilled and back in use the same day, and we will walk you through what we found and what we did.

What we check before we start

Before any flushing, we test the system water and check the radiators, the boiler and the pump. This tells us whether sludge really is the cause, how bad it is, and whether the system is suitable for a high-flow clean. On older or fragile pipework we adjust our approach, and if a system is genuinely too fragile we will say so rather than risk it. There is more on this in our guide to whether a power flush can damage old pipes.

If you are not sure whether you need a power flush at all, our symptom checker gives you an honest first read in under a minute, and you can send us a photo of the water when you bleed a radiator.