DIY Doctor

Help! Only some radiators work?

Postby dckt » Thu Jul 26, 2007 9:38 pm

Hi all,

I'm a newbie on this forum so apologies if this has been asked before. My wife and I are looking to buy a house and we tested the central heating. I'm pretty sure it's a Convential Boiler.

We let it run for about 30 mins and noticed that it quickly heated the kitchen, ground floor bedroom, ground floor toilet but not the 1st storey room, toilet or reception, or the 2nd storey room or toilet. So only about 4 were working out of the 10+.

Would there be any reason for this? the others were very quick to heat up, in a matter of 5-10 mins. My concern is that there's something majorly wrong and we'll have to fix it.

Would we have to bleed them to test it? (Just read about bleeding) Could it be anything else?

THanks in advance for any advice!

Rank: Labourer
Progress to next rank:
Posts: 2
Joined: Thu Jul 26, 2007 9:31 pm


Simply Build It

Postby DONFRAMAC » Fri Jul 27, 2007 2:10 am

Yes, it is very likely that bleeding is all that is needed. When a C.H. system is left unused for a while, rusting in radiators continues, liberating hydrogen gas, enough to cause airlocks. Bleed screws (grubs) are fitted at the top of all radiators, and release gas using a small brass or zinc key, but switch off the pump while bleeding, and repeat a few days later.
If the bottom of radiators are cold (you can check this now, before spending effort on bleeding), there is sludge build-up, which a plumbing firm would tackle best using powerflush pump & chemicals, which need to be rinsed out before they refill and prime the whole system for you, with anti-corrosion fluid. For £600 it saves you a lot of scuttering about, with DIY methods.
Rank: Ganger
Progress to next rank:
Posts: 195
Joined: Fri Mar 30, 2007 5:52 pm

Postby dckt » Tue Jul 31, 2007 11:42 pm

Thanks for the reply donframac!

Again being a total novice in plumbing, I went to the place again to check out the heating for 45 mins. It was the same story. I noticed that the heating system had a Grundfoss 15/50 selectric bare pump.

Question 1 - What is this pump for?

Question 2 - Without having to bleed the radiators, is there any other way to tell why some radiators aren't heating.

Question 3 - When I listened to the cold ones, it sounded like water was actually running through them. What does this mean?

I so need help!

Thanks in advance.

Rank: Labourer
Progress to next rank:
Posts: 2
Joined: Thu Jul 26, 2007 9:31 pm

Postby htg engineer » Wed Aug 01, 2007 4:00 pm

The pump is what pumps the hot water round the heating system. Upstairs radiators will get warm because of gravity but the water needs to be pumped to heat downstairs radiators and to keep all radiators hot.

The radiators will probably just need venting, the water might be passing through the radiators, but its probably the pump running that you can hear. Vent all radiators with the heating turned off until water is present at the bleed valve.

Not a major problem when buying a house. You know the boiler is working because some radiators get hot. The others might be full of air, blocked or maybe turned off.

Air, blockages etc can all be sorted later on.

The pump will have 3 speed settings, try turning it up. Or trying turning valves on other radiators down or off and see if the cold rads now heat up (known as balancing the system)
htg engineer
Rank: Project Manager
Posts: 3256
Joined: Tue May 22, 2007 5:22 pm

Display posts from previous
Sort by
Order by

  • DIY How to Project Guides
  • DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!

  • Related Topics