C/H Rad question

[JABB]

Our rads in out house heat up but only the top half. Why is this, and what can we do to get a full heated rad?
Thanks

[mrsxllifts]

Is it a new system or is it an established one and the problem has only just started?

Only ask as we have seen the flow and return fitted round the wrong way.

[JONSCZ]

Hi James.
Assuming it's an old system, then have a look here http://www.ukplumbersforums.co.uk/central-heating-... and you'll see that the problem is likely to be sludge in your rads. Sometimes a powerflush will fix it - prices vary widely British Gas charge upwards of £600 for it - so if you go down this route, then shop around - the forum link above suggests that £20 / rad + cost of new chemicals is a very rough starting price. If you only have 3 rads, then its going to be more / rad and if you live in a 15 bedroom mansion, then I'm sure there'll be room for negotiation!!!!!
HTH, Jon

[Ricky_M]

Top half heating is usually poor circulation.

Can be caused by an Air Lock, but if all of the rads are doing it, you probably have a build up of sludge in the system.

Bleed some water out of one of the rads and see what colour it is.

[JABB]

The system is probable 6 years old, although it has only been in use for 3 years ( Long planning story )
The liquid is black that comes out of the bleeder

[Ricky_M]

If its black, that is a good indication of sludge build up.

A powerflush is the quickest and most effective way of solving the problem, but is expensive.

Alternatively you can add a chemical to the system to break down the sludge, its a slower acting method, usually over a few weeks and you need to flush the system thoroughly afterwards to remove the chemical, which can be a pain if the downstairs rads pipework is supplied from above.

It could be a different reason though, get a decent Plumber to have a look and don't mention the word Powerflush until he makes a diagnosis!