Problem with radiators - help needed (PigletJohn???)

[HortenMarket]

We have just moved into a detached house (from a terraced) and are trying out the radiators big time today (as it's bloody freezing outside). We have a problem where most of the rads are hot at the top and luke warm at the bottom. We have an open vented heating system (megaflo for the water). We have changed 5 rads upstairs recently and there was a power flush completed on the system in June before we moved in. Do we have a sludge problem or an airlock or is there something else going on? I hate being cold and obviously realise we have a larger house to heat so want the heating tuned to perfection. Any ideas out there?

First though was sludge but you've had them done

Is it all the radiators?

New ones need to be balanced to let the right amount of water through to heat up properly, insufficient water flow or pressure from the boiler will cause the problem you describe

Did you get any guarantees on the work you had done?

We have a receipt from the power flush but don't know the plumber but could call and ask. The rads were changed by another plumber so not sure regarding a guarantee. A couple of rads are ok and completely hot but majority are hot at top and less so at bottom. Can balancing be done by us? DH very good at doing stuff and fixing problems.

It's most likely air in the radiators. Do you have a radiator key? If not any hardware shop will sell one (I'm assuming you have normal ish radiators - then the key goes in at the top at the side).

If you turn the key slightly you should hear air hissing out (hold a cloth beneath the key) - don't completely turn it or you'll have water pouring out - just do it gradually and let all the air hiss until you feel water dripping - then tighten it up. You should feel the radiator getting hot all over.

I think you're supposed to start at the top of the house (but I could be wrong). In older systems this should be done every year!

Ok I thought if air was in the radiators and they needed bleeding the tops were cold rather than the bottoms. Could try this though as it may help.

It's not air, air makes it cold at the top and hot at the bottom

You can balance them yourself if its water flow due to the valves on the radiators (look up tutorials on YouTube) but if its the boiler then you need a professional, it's not just a case of topping up the pressure manually

Ok DH is having a go at balancing them. Also wondering if the problem could be the thermostatic controls on some as the pipe leading the a few rads are really hot and the rad itself lukewarm. Thanks for the info.