Central Heating Question

Having new combi boiler fitted. is it ok to have the old gungey water running around new boiler? or should radiators be drained?

will the gunge and old water affect the effectiveness of new boiler?

9 Answers

Best Answer

When you fit a new boiler it is best practice to flush the system to clear any resideu and solder from installation, regards Terry.

Answered 6th Oct 2011

tm property services

Member since 9 Mar 2011

The system should be tested and power flushed if necessary. Benchmark requires all systems to be flushed.

Answered 6th Oct 2011

BDF plumbing and heating services

Member since 12 Nov 2008

No feedback

the one thing that will kill a new boiler is crap,gunge,black iron call it what you will!!or the installer!!!! it needs to be drained,flushed cold,sludge remover put in run on max for a few hours then drained again hot,then flushed for a while with fresh water.then you put sentinal X100 inhibitor in to protect the system,and the boiler.look at the instructions that come with the boiler (it tells you that)you can also fit a magnaclean that will continually pick up for years anything that is left,and they do work!!!!a sick of repairing bad instalations plumber.tom clydebank plumbing&heating.

Answered 6th Oct 2011

clydebank plumbing and heating

Member since 14 Apr 2011

When your boiler is fitted the system will be drained and flushed, also your should have a magnaclean or similar to keep the system clean

Answered 6th Oct 2011

House Doctors

Member since 13 Jul 2011

Your installer should ensure that the boiler is fitteed, as per manufacturer's instructions ! ! !

This would include, either, chemically flushing, or power flushing the entire system, prior to connecting / commissioning new appliance .

Old, as you say Gungey water, running around system is not good, though the hesating / hot water may still work !

It's all about the reaction between the different metals used within the system. :
Primarily the reaction between the copper &m Iron components.

These ususally allow the water to start forming ferous oxide, which I believe is the Gunge you are talking about.

Post the full job on this site ! !

I am sure you will receive approrpiate responses.

Adrian Hagger,

Answered 6th Oct 2011

Southsea Plumbing, Heating, Electrical & Gas Services

Member since 8 Nov 2010

If you are having a new boiler fitted be it combi or conventional the existing system must be power flushed with chemicals and treated with a water inhibitor on completion,this is something that is recommended to be carried by all boiler manuafacturers such as wocester etc,if this work is not carried out most boiler manuafacturers will not honour the warranty on parts and labour,and make sure your installer is gas safe registered

good luck

Answered 6th Oct 2011

The Bathroom & Heating Co Ltd

Member since 12 Nov 2010

All systems should be cleaned before a new boiler is fitted this should be in with the price that you have been quoted and yes the system will be drained.

Answered 7th Oct 2011


Member since 1 Jun 2008

I always powerflush when replacing boiler and install fernox f1 in primary return to filter any future metalic and non metalic debris from entering heat exchanger of new boiler.

Answered 8th Oct 2011

Rayhills Heating and Construction

Member since 26 Aug 2011

you should always flush out old water content as you dont want sludge to deposit in new heat axchanger , then fill with suitable inhibitor to protect new boiler and system.

Answered 7th Oct 2011

Total property maintenance

Member since 19 Sep 2011

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