New combi boiler-risks

teddysmum

We have a 40 year-old semi with a 35 year-old central heating system and the boiler needs replacing. We are considering a combi , as there are only two of us and it would be nice to have the extra space in the airing cupboard. However, I am alarmed to have just read a thread where someone had burst pipes, following installation and people have commented that this could be due to the extra pressure in the system.


Is this common and does it tend to affect properties much older than ours ?


Amended question: Is it common with a property of the age ours is ?

southcoastrgi

teddysmum wrote: »

Is this common and does it tend to affect properties much older than ours ?

yes & yes

weak joints, weak pipes & weak rads could all lead to leaks when changing to a sealed system

Knill

I don't believe pipes could burst from from the pressure in the system, there are safety features in place, such as a pressure relief valve, which would release the pressure from the system once it has reached a certain amount (Normally around 2.5 to 3 bar).

I recently went to a plumbing convention with college and one of the stands were showing off their fittings, which failed at around 70bar from what I can remember, the fittings were on copper pipe which was perfectly fine even after that extreme pressure.

The only pipe bursts I have seen are from pipes freezing, which puts a split in the pipe.





Edit -
When I read burst, I imagine water gushing out non-stop.

Yes you can get leaks like southcoastrgi said but from my experience, it does not happen all that often.

We change radiator valves when we do a conversion so that eliminates rad valves leaking from the extra pressure, unless they drip in which case they just need a tighten up

Only ever seen 2 rads which leak from the actual radiator, which is just a pin-hole hole in the radiator which dripped very very slowly.

Never actually had any pipes split when we have changed a system.

Weak joins can leak but it isn't as bad as you may think, its a simple drain down and re-solder or re-pipe that little bit.


As long as you get someone that do a proper job and properly check after they fit the boiler, you should be fine.

southcoastrgi

but it can happen, the trouble is that people replace boilers, sometimes rad valves & pumps, rads, but they very rarly replace the pipes & fittings, most old systems are dirty & full of sludge which will create pin holes & weak points,

I'm not saying it will happen with the OP's system but it would be amiss of anyone to say it's not gonna happen when changing from an o/v to a sealed system

Knill

Yeah I agree but like I said, different opinions of what's classed as a burst

diywhynot

Pressure test the system then you'll know.;) It is not always possible to visually check system e.g buried/boxed in/concealed pipework etc.We would be lacking in due diligence if the customer was not advised that conversion of an open vented to sealed central heating system can reveal pre-existing weaknesses in the pipework, radiators and associated valves. We attach a disclaimer to all conversion or powerflushing quotes. Example here.

teddysmum

So a good installer would pressure check the system and that would immediately show any problems ?


I'm already in a tizz over this as I'm dreading the disruption of having the job done anyway. Today is the first time I've heard about possible problems, so I'm near panic, but we have to have a boiler as ours is broken, so we are using kettles for hot water.

southcoastrgi

tbh no i wouldn't, if your heating system is full of sludge the last thing you want is black dirty water leaking out, if the customer wanted a pressure test done prior to deciding on a new boiler then i would do it after a flush then it would be clean water if it leaked & also the flush may uncover weak points on the system which might not be there before the flush

I_have_spoken

The problem is to get the guarantee on the Combi you'll likely need an expensive power flush and chemical clean which will also open the pinholes in old pipewotk and valves.

Even after a clean, sludge can migrate and quickly block the heat-exchanger on the new boiler which are shoddily made in China. With an old system, you should also install a magnetic filter in the 22mm pipe return to the combi.

Also insist the condensate drain is run to internal waste, don't allow them to bodge a 22mm pipe to an outside wall where it'll freeze an knacker the boiler.

teddysmum

How old is 'old' pipework ?

diywhynot

I_have_spoken wrote: »

Even after a clean, sludge can migrate and quickly block the heat-exchanger on the new boiler which are shoddily made in China.

For benefit of all, could you please identify which boiler brands are 'shoddily made in China'?