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Conflicting advice received from two plumbers regarding new combi boiler fitting. who is right?


My boiler is over 10 years old, some of my pipes are copper and the radiators are old. I decided to get a new boiler as they current one keeps losing pressure and needs refilling over few days. Its a two bed mid-terrace and I might want to get a power shower in one day as my shower has useless pressure. The ceiling are 16foot high so the house is cold. My heating bills are about £100 a month.

Plumber 1 who quoted £1850 for a Worcester Junior said he would only need one day for the job. he said he would do a 'Combi flush' and that it took about ten minutes on each radiator.

Plumber 2 said he wouldnt put a Worcester on my existing system as they are 'A bit like Jaguar cars, the best there are but they need everything else working perfectly or else they dont like it. ' He said the system would need a flush the ay before which would take 5-6 hours, using chemicals to break down the gunge in the radiators. he showed me the pyramid shapes cooler spots on the radiators (was on 3 radiators), he didnt sound overly excited about this recomendation and when i pushed him about it, he said really if i was going to be spending around 2k on a new boiler and flush, he'd suggest a complete system change. I'm waiting for his quote on that.

I told plumber 1 and he said plumber 2 was conning me. He said a flush of the radiators didnt take anywhere near a day's work. It was ten mins per radiator. The entire boiler fit and flush could be done in one day. He said and there was no need for me to have a system change. My radiators were fine.

Who do I believe? And what is a 'combi flush' plumber 1 is telling me he'll do? Is this the same thing as what plumber 2 is talking about?

5 Answers from MyBuilder Heating Engineers

Best Answer

Put these two quotes and get another one. The cost of the boiler alone on the first quote is excessive for the heating requirements of your property.
Power flushing should be carried out using system cleaner and then a suitable inhibitor , so therefore should be started the day before.
I would be inclined to side with plumber no 2 advice.


Answered 1st Mar 2015

All boiler manufactures state that the heating system MUST be clean prior or after commissioning of the new boiler installation, we as heating engineers have to decide whether the existing heating system needs to be power flushed or just chemically dosed preferably before the boiler is replaced, this time period gives the cleaning agent long enough to breakdown any solids (sludge) and other debris. A heavily contaminated (poor circulation) heating system is easy to recognise, the boiler is kettling (loud noises) some or all of the ground floor radiator are only warm or even cold. In this instance power flushing is strongly recommended, as being the most effective way of cleaning your heating circuit including all radiators.

But if you have not identified these symptoms previously mentioned then a pre or post chemical clean is sufficient. I would also highly recommend that your installer fits a magnetic filter, this valuable piece of equipment will not only help keep your heating system clean but will also ensure that the heating system runs more efficiently thus saving on fuel costs.

Plumber 2 seems to have a better grasp of the situation than Plumber 1. As for your comment 'system change' I think you mean complete 'system clean'

To effectively power flush an average heavily contaminated heating system
takes me 4 to 5 hours, and on completion I issue the customer with a certificate and a 1 year warranty guaranteeing my work. Ask number 2 plumber if he too offers this warranty, if I interpret his recommendation correctly!

A final query, you call them 'Plumbers' I hope you mean Gas Safe heating engineers? Check if they are Gas Safe registered if not already done so!


Answered 1st Mar 2015

10 plumbers, 10 different schools , 10 different boilers recommended :-)
Connect machine 1hr, flush 10-15min each rad, total 4-5 hours including cleaning mess. "PowerFlush" as far as I know is registerd trademark of British Gas, but we all call hoover a Hoover. Combi flush may refer to combination of flushing machine and MagnaClean attachment, which make cleanig procedure much more eficient (and quicker). If you have very old panel radiators without convector ribs on the back, replacement is recommended, as they will be not as efficient with new boiler (lower work temperatures).


Answered 1st Mar 2015

Plumber 2 sounds like he is doing the job properly, an old system would need a power flush which can take a full day.

Plumber 1 is likely going to remove the radiators and run a hose through them which is not going to flush the system


Answered 1st Mar 2015

Plumber 2 is on the correct path. Too many plumbers want to cut corners and rush jobs and do everything in one day. A proper powerflush 4-5 hours minimum.


Answered 12th Mar 2015

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