Purging a Central Heating System...

Adrian_J

To summarise a long story....

About 8 years ago, whilst I was away on annual camp with the TA, our Central heating failed. According to the engineer who my gf at the time (now Mrs) called, the system needed de-sludging and cost an arm and a leg, but she had it done for obvious reasons.

Now recently my boiler has started to play up, making noises etc and the Ch doesn't always work, other times it does. We have homecare200 (guess I should find an alternative in these forums) and they sent an engineer and things improved.

But still doesnt always work - unless the radiator valves are fully opened in most of the rooms. Obviously heating empty rooms is not a sensible plan...

So I am guessing that the system needs purging or cleaning.

Any one recomend and simple DIY sites on how to do it?

As far as I understand, I have a closed system, as I leave in a flat. The boiler is a Potterton Puma combi boiler approx 15 years old suppling 6 radiators. it is a one floor flat we live in.

BG have recnetly quoted us a new boiler install about £2300 before the various offers kick in. The quote includes £204 for a powerflush. So options are:

• Get a new boiler installed including powerlush
• Get BG or a local plumber to do a clean of the system cost - unkown
• Investigate doing it myself - ut not sure when before Christmas

Any advice suggestions would be most appreciated.

Adrian

ormus

http://www.vhsdirect.co.uk/site/product.cfm?id=D84FB850-AAAF-1188-EBFB9E903504A105

the chemicals cost about 20 quid. so diy about 100 quid total.
plumbers charge 200/500 to clean out a CH system.

Adrian_J

ormus wrote: »

http://www.vhsdirect.co.uk/site/product.cfm?id=D84FB850-AAAF-1188-EBFB9E903504A105

the chemicals cost about 20 quid. so diy about 100 quid total.
plumbers charge 200/500 to clean out a CH system.

Thanks for this.

Would I need to drain the system first to try and remove some of the sldge from the system?

Would it be worth while draining as much of the system first, then add the ferrox chemical before re-pressurised the system?

Then leave it for a week r so before repeating te process?

Adrian

ormus

i usually drain the system and refill and drain again. that gets rid of some muck. flushing with cold water is free!
then do the chemical bit.
you will have to drain the system a little bit, to fit the stuff in. see instrucions to how long to leave it. some say only run CH for 15 minutes. then flush again and add the protector.

http://www.diydoctor.org.uk/projects/drainch.htm
this is a how to, for an open vented system.

Adrian_J

Thank you again, most appreciated.

What protector do you use?


Just been looking in the cupbaord where the ch system is.

There is very little clearance between the floor and the tap. So what is the best way of emptying the system?

Is it just to open the ale and let hs system rain into some suitable receptacle ?

Sorry - whilst my DIY skill are above average, I have not done much plumbing

Adrian

Adrian_J

Found this site which looks useful

http://www.diyhowto.co.uk/plumbing.htm

Only problem is that I live in a secod floor flat so disposing the liquid into an external drain is not an option.

But I will have a think, any suggestions?

Adrian

Stompa

You may find some useful info here:

http://forums.moneysavingexpert.com/showthread.html?t=83083

adaze

Adrian_J wrote: »

Found this site which looks useful

http://www.diyhowto.co.uk/plumbing.htm

Only problem is that I live in a secod floor flat so disposing the liquid into an external drain is not an option.

But I will have a think, any suggestions?

Adrian

hosepipe?!?

Mutton_Geoff

I agree with Ormus, with the added bit that if your pump has selectable speeds, whack it up to full speed and run the heating with all radiators fully open (both valves on each side, one will require a small spanner or "borrowing" the knob from the adjustable side to open it). The idea is to try to get the sludge into solution and around the system.

Drain from the radiator valve into the toilet with a hosepipe. If you are careful you should be able to get all the water out except the last bit in the pipe which can then be decanted into an oven tray and poured down the loo.

Repeat the exercise (as Ormus said, water is free). Then add the cleaner and follow instructions! Don't be tempted to leave it in a week.

Repeat again then refill adding Fernox or equivalent inhibitor. Bleed all the radiators and run the system. Once it's all working, make sure you balance the radiators. This is the most effective Moneysaving thing you can do as it makes the boiler work most efficiently and gets those cold radiators (usually furthest from boiler) piping hot.

unless the radiator valves are fully opened in most of the rooms

As above, make sure you balance the system once you finish and the system will perform never as before. Most plumbers don't know or have the time to properly balance a system (it takes several hours) but the results are worth the time.

Adrian_J

Thank you all for your suggestions.

I have an idea for discarding into the commuanl waste pipe - I have access via the kitchen waste pipe.

I am still unsure how to set the setting on the various valves to allow me to flush the system with mains water afterwards.

I have BG coming this afternoon to give me a quote but the heating is currently working - but this either off or too hot at the moment; as soon as I close the valves to reduce the temperature, the system fails

So I have some reading to do but I am very tempted to at least flush the system myself first before adding the Inhibitor. Just need to buy/hire the pump thing in the original reply to my first post.

But if I buy it I can do it annually I guess


Adrian

Mutton_Geoff

if I buy it I can do it annually I guess

It shouldn't really be a routine maintenance item, and certainly not an annual task! If the system is sludged it's because of lack of inhibitor or stuff has lost it's potency over time.

I wouldn't bother with a powerflush, just drain and refill as suggested above. It's a cheaper option to try first.

As for the heating being too hot and/or shutting down, sounds like a symptom of a poorly balanced system. A radiator that is too "open" will pass very hot water back to the boiler causing it to shut down. A temp drop across the system/radiators (usually 12 degrees C) is required not only for boiler efficiency but to assist in it's cooling during operation. Your boiler handbook will have the required temperature drop stated.