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Dodgy Rads After Boiler Issues and Power Flushing

Postby Lulubradders » Mon Dec 17, 2018 8:34 pm

Ok so I have had issues with my boiler for the last 3 years, I recently had a power flush, all the rads were taken off and flushed through as well. That was 6 weeks ago and now only 3 rads work but are only lukewarm the rest don't come on at all, and every day another one fails. The hot water is fine, I have bled all the rads but nothing seems to be helping. Any ideas? Could it be the pump? as surely it cant possibly be sludge in the system still.
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Postby ericmark » Thu Dec 20, 2018 9:58 am

I will guess lock shield valves not set up correctly.

Starting with a radiator that works, nearest to boiler, turn off lock shield valve (tap opposite end to TRV) allow pipes to go cold then with boiler running and TRV set to max, open 1/4 turn at a time with couple on minutes between each turn, until you feel hot water in either of the pipes, then stop, normally around 2.5 turns.

Then repeat for each radiator slowly moving away from boiler, water takes easiest route, it's not the radiators which don't work that is problem, it's the radiators that are work have too much flow.
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Postby Browndoff » Sat Jan 12, 2019 3:35 pm

Ericmark might well be correct but another possible explanation does exist.
Apart from sludge [which is soft and relatively easily flushed-out], there can be hard limescale in the rads and/or the pipes between them. When the flushing was done, you mentioned the removal of the rads and individual flushing of each rad and the boiler - but you might have dislodged hard material from any one of these and THAT might now be blocking the pipes.
I had a similar problem some years ago and I flushed the rads & boiler and then reassembled the system and then flushed the WHOLE thing. Quite a lot more nasty stuff came out!
If there is not currently a drain fitted at the lowest point in the system, it's not difficult to add one and it's essential for flushing the whole system.
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