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Central Heating

Combi boiler install

I have y plan system in home and want to change to combi . But few engineer said chances are there u may have leak with pipe because my house is 50 year old, some said not. Can anyone advise pleas

5 Answers from MyBuilder Heating Engineers

Best Answer

You have old imperial copper pipe with old soldered joints. So in simple terms Adding a Combi boiler will increase water Bar pressure pressure through the cold / hot water supply pipes (not the heating pipes) and can easily burst old soldered joints.
Your current H&C water to your bath and basin etc (excluding your kitchen sink tap and a loo possibly) is fed from a black tank in the loft (cold) and a cylinder in the airing cupboard (Hot) and neither produce no more that 0.5 bar head pressure at a guess. No idea how your house is set up though.

My advice is remove all pipes and start over. I bet you have lead pipe still in the loft too.


Answered 17th Jun 2020

My advice would be as follows..yes there is always going to be a risk of leaks changing a system from being tank fed to being pressurised etc however As far as I am concerned wether the pipe work is imperial or metric makes no difference if anything the copper was a lot thicker.. Should you be unlucky and solder joint fails.. Happens to 1 in 10. I would recommend to change all old rad valves at a least and use a engineer / company with experience hope this helps kind regards Daniel


Answered 16th Jul 2020

this is because of the increase in pressure that a combi boiler would increase the working pressure of your central system,this could lead to leaks on pipework and radiators ,also most installers would not want to power flush a system of this age as this may also cause leaks,most systems of this age are actually not fit to be converted to a higher pressure system.a combi boiler will up the pressure in your central heating system from atmospheric to 1.5 bar and can lead to leaks in the system,as it will also increase pressure in domestic hot and cold services that could lead to leaks,not as jack the plumber states it will increase pressure in both systems.


Answered 17th Jun 2020

The answer which pipe can start leaking is possible, but the chances are minimum. The systems has been changed in millions property and probably only 1% chance could happen. For 1% chance could happen the don’t have to start ripping off the pipe work. They can start changing the system in worst case they may have to repair one or 2 leak 1% chance. I changed more then 100 System never happen too me.


Answered 12th Jul 2020

I’ve done a lot of these system change overs and never had any problems your pipe work as obviously stood the test of time and the increase in pressure should not make much difference.
Hope this helps


Answered 16th Jul 2020

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