Central heating chemical flush

[Justwingingit2005]

Hi all

I noticed one radiator has not been getting as hot as it did previously. Hot at top colder towards bottom.
Plumber came out. Said thinks it's sludge and put a chemical treatment in. We switched heating on for 2 hours while he was here then then had it running as normal.
He is due back in just under 2 weeks to finish.
Here is my question. When should we know if it's worked? Over the next few days? When he's flushed the system out?
Maybe I'm expecting it to work instantly 😕
But I do think some of the other radiators without an issue seem hotter.

.

How old is the system?
Have you had the boiler replaced ?
Do you have a magnetic filter in the system ?

I would probably just get the radiator replaced if it was sludged up.

Provided you haven't got some sort of stupid expensive radiator the radiators are actually quite cheap and I doubt whether the labour charge for the chemical flush (which probably just moves crap around the system from one place to another) is much less than fitting a new one.