Is a power flush needed?

naughtysmurf · 10-11-2025 09:20AM #1

So we have gfch, house built in 1997, newish boiler approx 3 years old with magnetic filter, serviced every year, we’ve 12 rads, ONLY issue is one of them is not heating due to sludge I’m told, all others rads are piping hot

A gas service guy says we need a power flush, does this sound right?

Is power flushing common, never heard of it before & don’t know of anyone who’s had it done?

Thanks

Lenar3556 · 10-11-2025 10:16AM

https://www.boards.ie/discussion/2058428134/is-a-power-flush-needed

Maybe. Sludge forms from rust and other deposits that break down from within the heating system. It can affect circulation, and is a common issue.

Power flushing aims to pump that out using high pressure and chemicals. It’s usually effective, but there are risks - already weakened pipework or radiators can suddenly begin to leak afterwards.

If the issue is with just one radiator; I would first establish that it isn’t simply a balancing issue. Once that is ruled out, that individual radiator could be removed and flushed outside with a hose. The local pipework could also get some localised treatment and hopefully resolve the issue without resorting to a full flush.

It’s a good idea to add inhibitor to the system every couple of years. It can be easily done at the magnetic filter - it goes a long way to stop future sludge formation and corrosion.

naughtysmurf · 10-11-2025 07:56PM

The pipe ( I assume ) feeding the radiator is hot, no heat after that valve you turn to turn it on & off, all others rads hot. The rad in question is upstairs if that matters.

What I know about plumbing could be written on the back of a stamp

winklepicker2025 · 10-11-2025 08:00PM

if the pipe is hot going too the rad,pop the rad down and flush it out with a garden hose.

Do both top & bottom.

While rad is off flush the pipe work out via the filling loop.

naughtysmurf · 10-11-2025 09:01PM

Filling loop?

naughtysmurf · 10-11-2025 09:22PM

I’m confident enough to do the following,

Close the valves either side of the radiator, loosen the nuts either side, remove the rad to the back of house & hose it out as best I can & reattach. Open the two valves, after that I know nothing & I’m just hoping for the best & that I haven’t negatively affected the heating system as it’s 99% working currently or I’ll be getting it in the ear from the mrs, it’ll be a job for Saturday.

NickNickleby · 10-11-2025 09:23PM

This happened to my mother recently. Identical symptoms. The pipe feeding the hot water into the rad was hot, but the rad was cool. So I checked to see if it needed bleeding, but only water came out of the bleeding valve. So then I suspected the thermostatic valve. I removed it and looked at the pin sticking up out of the valve body. On a whim, I used a large pliers to press it down and let it back up slowly and very gently, and after a couple of goes, it popped up all the way (probably less than half a centimeter) the water started flowing through the radiator - i could hear it rushing through and the rad started heating immediately, Now, having said all that, I'd be amazed if your plumber hadn't tried that already.

Be aware, I'm not a tradesman, just a very lucky diy'er.

Edit to add, YouTube for tips on removing the thermostat.

winklepicker2025 · 10-11-2025 09:44PM

filling loop is what tops the heating system up with water,normally located in the hot press or beside the boiler.

Once you open the radiator valves the system will empty so you then open the filling loop and it refill the system but leave it open and it will flush out any build up that may be in the pipe work.

The pressure may not be great but it’s better than nothing.

A picture of hot press would identify the filling loop for you

Lenar3556 · 10-11-2025 10:20PM

https://www.boards.ie/discussion/comment/123978599#Comment_123978599

Install is from 1997 - more likely to be an open vented or semi sealed system.

naughtysmurf · 11-11-2025 07:44AM

So if I do what I said I’d do, after I reconnect the rad, is there something else I have to do before turning on the gas boiler? Will the water just automatically start flowing into the now empty rad once I reopen the valves at either side?

Thanks for the inputs by the way.

Its an ideal logic system s24IE if that matters

Yes the installation is 1997, no thermostatic valves, just the old turn on / off ones same as what I grew up with in the 70’s & 80’s

winklepicker2025 · 11-11-2025 10:31AM

you’ll have too top the rad back up once it’s reconnected

naughtysmurf · 11-11-2025 11:26AM

https://www.boards.ie/discussion/comment/123979400#Comment_123979400

how do I do that?

naughtysmurf · 11-11-2025 10:38PM

There is a top up valve just below the boiler, after refitting the radiator, I’ll open this fully, there is another smaller yoke feeding this top up valve to turn until I hear water flowing, keep an eye on the gauge & shut off water before gauge reaches 1.

sound about right?

If so, only other thing I’m not sure of is the original position of the lock shield valve, not sure what to do about that?

Is a power flush needed?

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