How do I descale my central heating system

[Nick]

My central heating is controlled by a combi boiler. Occasionally the hot water doesn't come on when the hot water tap is turned on. Having spoken to a plumber he says that the problem a valve in the boiler getting stuck because of a build up of limescale. The boiler also ?buzzes' a bit when the heating is on. He has advised me to descale the system using descaler fluid.

Can anyone advise me how to descale the system ? the plumber advised on draining a radiator and topping it up with the fluid ? how do I do this ?

Cheers Nick

[Owain]

"Nick" wrote | My central heating is controlled by a combi boiler. Occasionally | the hot water doesn't come on when the hot water tap is turned on.

Is this *a* hot water tap or *any* hot water tap?

If the problem is one particular tap, it's probably a tap problem; google for tap reviver as this was discussed a few weeks ago.

Owain

[raden]

In message , Nick writes

Does it come on for a short period ? This would indicate limescale

I think you would be wise to post more details to the group in order that a proper diagnosis might be made

what boiler for example

[Nick]

Hi

Thanks for you?re responses.

I don't know much about boilers and plumbing but here's a description of what's (I think) is happening.

When I turn on any hot water tap, sometimes there's no hot water. I turn the tap off and then back on an there's an audible click from the boiler and the boiler fires up - producing hot water from the tap ? this can take several attempts. A plumber has advised that in the boiler there a valve that switches between hot water and heating. He stated that a build up of limescale may prevent this valve from working efficiently. Adding descaler to the system, he said, would cure it.

I don't know the details of the boiler - I will get them and post them tomorrow if this helps

Cheers Nick

[Andrew Beck]

My combi boiler had the same problem. The method of fixing depends on the boiler. Check the boiler manufacturers web site for the installer/service manual quite a few manufacturers make them available on the web.

My boiler use the venturi effect and diaphragm to actuate a micro switch.

The fault diagnostics that I went through were

1) Draw hot water at a high rate 2) Do you get hot water, No 3) Manually actuate the DHW microswitch, Do you get hot water, Yes 4) Check water pressure and clean inlet filter, Do you get hot water, No 5) Check diaphragm for leaks and actuating rod for limescale / corrosion, Yes to limescale / corrosion on actuating rod 6) Replace actuating rod so it moves freely, Hot work now works.

Adding a descaler to the system won't help much as side of the system you need to descale in the DHW side not the central heating side. So it's difficult and probably dangerous to put descaler in your mains water supply. The only way to descale them would probably be to remove the parts and descaler separately. (or just replace them as I did).

Andrew