Power Flush vs Magnetic Filter
One cleans the system, the other protects it.
These two often get confused, but they do completely different jobs. A power flush removes the sludge that is already in your system, while a magnetic filter stops new sludge building up afterwards. They are not really alternatives, they work together. Here is how they compare and when you need each.
A power flush and a magnetic filter are not rivals; they do opposite jobs. A power flush is a one-off deep clean that removes sludge already in the system. A magnetic filter is permanent protection that captures magnetite as it forms, so the system stays clean. A dirty system needs cleaning first, then a filter keeps it clean. On an already clean system, a filter plus inhibitor may be all you need.
Power flush vs magnetic filter at a glance
| Compared | Power flush | Magnetic filter |
|---|---|---|
| What it does | Removes sludge already in the system | Captures new magnetite as it forms |
| When | A one-off deep clean | Ongoing protection while fitted and maintained |
| Fixes existing sludge? | Yes | No, only catches what circulates |
| Prevents future sludge? | No, on its own | Reduces future sludge build-up by capturing magnetite before it settles |
| Best for | A system already full of sludge | Keeping a clean system clean |
| How they pair | Clean the system first | Then fit the filter to protect it |
When you need a power flush
A power flush is for a system that already has sludge in it. If radiators are cold at the bottom, the water runs black when bled, or the whole system is slow and noisy, the magnetite has settled and needs removing. A filter cannot do that, because it only catches what flows past it. The deep clean comes first, which is what our power flushing in London service does.
When a magnetic filter is enough
On a system that is already clean, newish, or has just been flushed, a magnetic filter plus a proper dose of corrosion inhibitor may be all the protection it needs. The filter sits on the return pipe and captures magnetite as it forms, before it can settle in radiators or reach the boiler. It is the low-effort way to keep a clean system clean, emptied once a year at the boiler service.
Why they work together, not instead
The honest answer for most sludged systems is both. A filter fitted to a dirty system cannot rescue it, because the settled sludge never moves past the magnet. And a power flush with nothing fitted afterwards leaves the system to slowly corrode and dirty again. Clean the system, then protect it with inhibitor and a filter, and it has a much better chance of staying clean long term.
A common and costly mix-up
Some people fit a magnetic filter to a sludged system hoping to avoid the cost of a flush, then wonder why the cold radiators stay cold. The filter is doing its job, catching what circulates, but it was never going to clear sludge that has already settled and stopped moving. The opposite mistake is paying for a power flush and then leaving the system unprotected, so it quietly dirties again over the following years. The sensible approach is to spend once, in the right order: clean out what is already there, then protect against what forms next. Diagnosing the system first is what tells us whether you are starting from a clean system that just needs protecting, or a dirty one that needs both.
Cost, and what to do next
A magnetic filter is the smaller spend, a one-off install. A power flush costs more because it does more. But on a sludged system the filter does not replace the flush you would still need, so the right question is what your system needs, not which is cheaper. See what affects the price, or send your symptoms and we will tell you whether yours needs cleaning, protecting, or both.
Power flush vs magnetic filter, answered
Is a magnetic filter as good as a power flush?
Do I need both a power flush and a magnetic filter?
Can a magnetic filter replace a power flush?
Will a magnetic filter clean my radiators?
Is a magnetic filter cheaper than a power flush?
What keeps a system clean after a power flush?
Clean it, protect it, or both?
Tell us about your system and we will say honestly whether it needs a power flush, a magnetic filter, or the two together. Clear quote before any agreed work.
