2 new rads not working

[favemuppet]

Have looked for a similar problem on this site but cannot find, so apologies if dealt with elsewhere!

Move into new house - built 1960s. CH system (combi) has big old rads and big steel pipes. 2 extensions were built last year by previous owner and these 2 rooms have new slimmer rads and thin copper pipes.

Problem I have is that these 2 new rads do not get hot. Plumber I know tried to balance the rads but no joy. He said that cos the old pipes were bigger the water was tempted to flow to these first so the new pipes would struggle. I do note that its not only the rad that stays cold but also the upright copper pipes.

He also suggested system needs flushing through as water in one of the new rads was black (which for some reason he couldnt do).

Does this sound plausible?? Is there actually another fault here?

[peter the plumber]

You’re dealing with a 40-year-old heating system.

Steel pipe is a sod and will need cleaning out.

The radiators are old and full of crap.

Power flushing would only cause the pipes/radiators to leak.

I don’t know how old your boiler is, but you should think about a complete renewal of your heating system.

New copper pipes, new radiators, new controls.

I hate to think what your heating costs are.

[favemuppet]

Couldnt say what the heating costs are as only been in a fortnight!

Boiler is only year and a half old.

[favemuppet]

What about a mains flush?

And how much typically to renew the system? Would need 5 rads and associated pipework.

[peter the plumber]

Power flushing on a new boiler less than 5 years old is unheard of.

They should have done it before they fitted the new boiler 18 months ago.

Has for replacing your current pipe work and radiators

It’s not the parts it’s the labour.

Good radiators start at about £100 each, then you will need trv and lock shield on each of them.

You will need new programmer, motorised valves and thermostats

Without looking at it, it’s hard to say

But a I think you are looking at about £800 for the new radiators, £300 for other parts and about 3 days labour.

About £3000, but without looking at your home it’s hard to say.

Look on your local trading standards web site for a good plumber and ask them round for a look.

[Manic Compression]

I would just like to add at this time that Power Flushing would not necesarily make the joints leak. Current Flushing systems increase the flow of the water in the system, not the pressure. This, combined with cleaning fluids left in the system a few days prior to flushing and agitating the radiators as flushing is performed, often makes a difference. Costs apx £300 - £400.

[favemuppet]

Someone has told me that this is a common problem with a "one pipe system". What is that?

[peter the plumber]

A one pipe heating system, means there is only one pipe.

Most have 2 pipes, one for feeding the radiators the other for used water.

On a 1 pipe system, the heated water go thru the first radiator and then back into the same pipe, by the time the water reaches the last radiator in you home, the water is not very warm and the last radiator does heat up every well.

The affect of this is simple, you boiler could be running at full power but after the water has gone thru 5-6 radiators it would have cool down and the last ones to get the water would be slow heating up or stay cold.

On a 2-pipe system, you have 1 pipe feeding the radiators with hot water, and a second pipe taking the use water back to the boiler for reheating that is better.

[Narc]

one pipe system is where you effectively have one flow coming from the boiler into the first radiator. the return of that radiator then becomes the flow of the next rad in the line and so on, very common in old houses.

Needless to say not great as it is not used today (generaly). one pipe systems are a pig when adding radiators to especially with the age of the heating system. even with a single pipe system you should be able to get some heat into the new radiators.

if its a single pipe system the pipes feeding the new rads should be the same as the rest.

[thedoctor]

See the projects section and read about central heating system. The one and two pipe system are explained with diagrams