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Discuss Whether to power flush a 40 year old central heating system? in the Central Heating Forum area at PlumbersForums.net

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Tim Hardy

I’m currently looking into replacing my 20- year-old Ideal Classic FF 360 gas boiler in a 70s semi and have been getting various quotes for a condensing conventional boiler, as we don’t want a combi.

The current boiler works well, we have it serviced every year via British Gas Homecare, but it’s less efficient than new condensing models and we’re concerned at it breaking down during the winter and parts being unavailable to fix it.

Our radiators are always red hot, no cold spots, only one small bedroom one and the tall bathroom towel rail needs regular bleeding.

My question relates to the system cleanse/powerwash options being offered by the different quoters.

All installers would drain the system and give it a chemical treatment to clear it out, but British Gas have recommended a power wash too, whilst one reputable local firm says they wouldn’t recommend power washing our older piping as it could cause leaks.

That makes sense, as one reason for avoiding the combi system is that we’ve been advised the pressure on the system would be too great.

The local firm’s method is to drain and put in a chemical treatment, have us use the heating an hour a day for a month so the chemicals can clean the system, then come back and drain the system before adding inhibitors.

British Gas seem to want to do everything in one day, which is perhaps why they want to power wash it, though they’re happy to just do a chemical treatment in one day and say it might be enough.

I’d appreciate any comments as to whether a power flush is inadvisable for us and also whether the British Gas method without the power flush would work, or whether leaving the chemicals a month is better.

Thanks.
 
Go with the local firm and the gentler method, a powerflush would probably be ok too but I wouldn't want to be overly reliant on a chemical flush done in a few hours unless the system isn't very dirty.
 
I would prefer the dose it and let t do its work method. Powerflush is fine and I wouldn't think twice about doing it but it isn't always necessary and it can cause issues on occasion.

Out of curiosity, how much more efficient are you expecting a new boiler to be?
 
It's a fair point by LP as you won't recoup any efficiency gains anytime soon (approx 78% v 90%) and a quick search reveals the availability of parts. Have BG Homecare been on about the age and availability of parts cos that's their usual M.O?


If it ain't broke...
 
I would prefer the dose it and let t do its work method. Powerflush is fine and I wouldn't think twice about doing it but it isn't always necessary and it can cause issues on occasion.

Out of curiosity, how much more efficient are you expecting a new boiler to be?
As the ops rads etc are operating perfectly I would do nothing, even if it invalidates a new boiler's warranty, I would install a good quality combined magnetic/particle type filter and motor on, I have a 50 year old OV system with some rads > 40 years old and my system is, like above, operating perfectly and wouldn't dream of any type of cleaning apart from a flush down if I was installing a new boiler.
 
@ John g... the OP's boiler has a cast iron hex as I suspect is yours so it would probably still work if you ran sludge through it. Unfortunately with increased efficiency comes design and materials that are less robust so system cleanliness and PH are far more critical to the longevity and function of a modern hex.
 
As the ops rads etc are operating perfectly I would do nothing, even if it invalidates a new boiler's warranty, I would install a good quality combined magnetic/particle type filter and motor on, I have a 50 year old OV system with some rads > 40 years old and my system is, like above, operating perfectly and wouldn't dream of any type of cleaning apart from a flush down if I was installing a new boiler.
I would take a water sample look at the turbidity, test pH, and see how corrosive it seems before deciding whether or not it needs to be cleaned. I would think that after 20 years, it will at least need a chemical flush but that is just my view. It may well be fine just emptying it as you said and installing a good filter.
I was commenting on which method as opposed to whether it had to be done or not. Obviously each situation should be taken on its own merit.
In my part of the world, boiler manufacturers Engineers are keen on water sampling. I would prefer they had no comment to make than tell my customers that the water quality is poor and their installer is to blame.
 
It's a fair point by LP as you won't recoup any efficiency gains anytime soon (approx 78% v 90%) and a quick search reveals the availability of parts. Have BG Homecare been on about the age and availability of parts cos that's their usual M.O?


If it ain't broke...
Agree if it aint broke ..... I am still persevering with my old system ..... and trying to sort out its problems.
 

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