CH System flush


My heating system is fully pumped with back boiler.When heating comes on the radiators upstairs are slow to heat up and I have been thinking that a flush out of the system may improve things.I have in mind just to open the discharge valve and get the pump running.Can anyone please tell me the pitfalls if any with this move and perhaps suggest a better way.Someone I know did something like Im going to try and got an airlock in his system and had to call gas engineers to get system ok again.I obviously dont want that but to get gas company to do a complete flush is very costly.I would appreciate any suggestions.
allan
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Logic and common sense should tell you that the last radiators in the ‘loop’ will be the least to warm.
Now, you tell me that your back boiler is on the first floor?
Wake up! This is normal and applies to every heating system.
tOTALLY bRAIN dEAD http://www.justservices.com/open/i/diy.html
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wrote:

Logic and common sense should tell you that the last radiators in the ‘loop’ will be the least to warm.
Now, you tell me that your back boiler is on the first floor?
Wake up! This is normal and applies to every heating system.
tOTALLY bRAIN dEAD http://www.justservices.com/open/i/diy.html
Well I have had system for a long time and had not noticed the long delay until the last couple of years but I think you are telling me to leave it alone so I will do.If it clogs up completely I will let you know :-)
allan
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It might well. Does each radiator heat up evenly across the whole surface eventually? During the period of slow heating, is the return pipe from the radiator cold/warm/hot? I presume that being a back boiler, it's probably a vented system (with a small radiator header tank)?

Only if the system isn't balanced, or has become blocked.
How dirty is the water in the system if you bleed a bit out?
It's probably worth doing a simple flush through. Do something along the lines of draining and refilling. Then run the pump with just one radiator on at a time, which may generate enough flow to stir up settled sludge. Ideally you want to fully open the lockshield valves, but this will lose the system balancing and you'd have to rebalance it afterwards. Then drain again. Don't let the pump run dry as you might be suggesting above -- pump bearings are water lubricated and will be damaged by running dry. (Pump is also water cooled, even though the water is normally hot.)
Other options which you could consider in bad cases are to hire the power flush kit yourself (it's not that expensive), or to remove each radiator and take it outside and clean out with a hose or pressure washer.
When you've got the bulk of the free sludge out, you could run the system for a while with a sludge cleaner additive in it, and then drain and refill again. That usually means running the system hot for some time, for which this probably isn't the best time of year! On the final refill, you should add an inhibitor, which prevents the corrosion which causes the sludge. In an vented system with a small header tank for the radiators, you should replace this once a year. For a sealed system, it will last much longer providing you don't need to top it up frequently.
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Andrew Gabriel
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wrote:

Thanks Andrew I was thinking along the lines of draining and refilling.I have tank in loft so if open drain valve and leave water to flow without the pump running would this get rid of some of the sludge without causing any problems.
allan
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If you open the drain valve and let the header tank carry on filling, you could leave the pump running. The occasional period with air in it probably won't do much harm, but you don't want to do that for a long time.
The sludge suspended in the water isn't actually whats going to be doing harm -- it's the sludge which has settle out. You will need to get this stirred up as I suggested above to get it into the water and thus ejected from the system.
However, you didn't answer any of the questions above, so it's not clear if this really is the problem at all.
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Andrew Gabriel
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