Central heating flush needed?

poppellerant

I've been decorating and had to remove a radiator from a bedroom, upstairs, to decorate the wall behind it. I closed the valves either side of the radiator, unscrewed the pipe on the lockshield (?) side of the radiator on the bottom, opened the bleed valve, then unscrewed the thermostat side of the radiator to empty it. So I didn't really have any issues emptying or refilling the radiator.

But what concerned me is that while emptying the radiator, almost black water with black bits came out. When I took the radiator off the wall, I tipped out even more of the water and bits away. The water was not sludge like at all and was power flushed around 2 years ago when a new boiler was fitted.

I'm not sure on what to do next. Refill the system a few times with plain water until it runs clear, then add some of central heating cleaner, flush a few weeks later then add inhibitor? Or just use the cleaner straight away and follow with a flush a few weeks later?

It's a Baxi DuoTec combi boiler which heats 5 radiators with no storage or hot water tanks.

I'd really appreciate any help and pointers to get this sorted.

phil24_7

I would drain it right down, refill, then put some sentinel cleaner in for a week or 2. Then drain the system fully and fill it up again.

Then run the central heating whilst filling and draining at the same time (try to balance in and out) until the water is clear.

Shut the filler tap off, then the drain. Add some sentinel inhibitor as you normally would the do you final bleeding/pressurisation.

Regards
Phil

unclebulgaria

Where Phils idea might shift some of the sludge the majority will be left at the bottom of the Radiator. If you're on a budget you could remove all the Radiators and manually flush them through with a garden hose. Then when they're back on you could try some X800 or F5 cleaner for a week, its a strong cleaner but not corrosive. Make sure to use the same manufacturer for the Inhibitor when you've drained the cleaner out.

poppellerant

I'm really considering this bundle of both cleaner and inhibitor. i just don't know how to introduce it into the central heating system from the bottles.

The express Fernox products are more expensive, but perhaps at a convenience.

phil24_7

Unless radiators have cold spots then there is unlikely to be a build up of sludge. Black water whilst not great isn't indicative of sludge build up and I doubt you would have it after just 2 years. Poor flow or hot & cold spots would be more of a concern.

I had similar to what you had and doing what I described cleaned it right out.

Regards
Phil

phil24_7

poppellerant wrote: »

I'm really considering this bundle of both cleaner and inhibitor. i just don't know how to introduce it into the central heating system from the bottles.

The express Fernox products are more expensive, but perhaps at a convenience.

You can buy a kit that has a lid and some tubes that will help you put it in the top of most radiators.

southcoastrgi

Sorry to disagree with UB but if you are going to do a manual flush ie without using a powerflush machine I wouldn't use X800 unless you manage to get all this out it will wreak your pump

unclebulgaria

southcoastrgi wrote: »

Sorry to disagree with UB but if you are going to do a manual flush ie without using a powerflush machine I wouldn't use X800 unless you manage to get all this out it will wreak your pump

Agreed its not brilliant to leave too much cleaner in the Heating Circuit but, When I spoke to Sentinel they told me that allowing the water to flush through for a decent time and adding there Inhibitor neutralises the cleaner. I know the cleaner isn't good for the Baxi/Potterton/Main brands as it makes the Thermistor fibre washer leak.


Just to add Phil, you don't need cold spots in the rads to have too much dirt/sludge in the system.

phil24_7

I still think it's highly unlikely to have a large sludge build up in the rads just 2 years after a power flush.

poppellerant

Today I flushed out the Fernox TF1 filter and the water was barely grey in colour and only a few black bits came out of it - compared to a few days ago, where I repeatedly flushed the dark water with lots of bits in until it ran clear.

So I'm hoping that the rubbish from the radiator was dislodged and caught in the filter and that the was the last of it.

southcoastrgi, in my position what you would do? I am prepared to drain the system using the lowest radiator in a few days time. But I would value your advice on what to use to clean the system before hand, before replacing the water with fresh water and inhibitor.