Gravity Fed CH System Question

Postby J4mes » Thu Feb 21, 2013 2:12 pm

I inherited an old gravity fed central heating system when I just moved. Its weird but the top up tank fills with hot water from an overflow pipe (not the cold feed controlled by a ball valve). This can't be right but I can't work out why this is happening. This makes the converted attic as hot and humid as a tropical rainforest and we have the constant sound of trickling water! Any ideas whats causing hot water from the system to constantly overflow and can anyone suggest how to fix the problem. Thanks in advance if you are able to help.
Rank: Labourer
Progress to next rank:
Posts: 1
Joined: Thu Feb 21, 2013 2:02 pm


Simply Build It

Postby 2tellytel » Fri Feb 22, 2013 11:56 am

Obviously not there to see exactly what set up you have but the pipe you describe as over flow, sounds like the vent pipe which goes to feed and expansion tank via the boiler and is installed to vent the system if it over heats. You can go to and click on "my plumbing" to see drawings etc.
However if you have a pump on the circuit, in some cases having the setting too high can cause water to pump out the vent especially if small no of rads.

Need to know more about your system to give definitive answer
Is your boiler solid fuel, oil or gas.?
Rank: Apprentice
Progress to next rank:
Posts: 16
Joined: Wed Dec 19, 2012 11:08 am

Postby collectors » Fri Feb 22, 2013 3:19 pm

Could be one of many things, but it sounds like the boiler stat is not working properly & making the system to hot. When this happens it will send the over heated system water up the expansion pipe into the loft top up tank.
Is the system very noisy & is the hot water taps giving out scolding water?. If so! get a boiler engineer to change the boiler stat.
Rank: Foreman
Progress to next rank:
Posts: 247
Joined: Mon Dec 01, 2008 7:26 am

Postby stoneyboy » Sat Feb 23, 2013 10:10 pm

J4mes ,
If you have tried turning the pump speed down and the overflow still occurs try increasing the height of the invert on the vent pipe.
Rank: Project Manager
Posts: 2715
Joined: Wed Dec 10, 2008 6:44 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