The Andy Hall of fame...

Excuse the bad pun, but Andy was never adverse to one of those!. This page is really a tribute to one of UK.D-I-Y's most prolific and respected posters. Although sadly no longer with us, his sage and detailed advice lives on in the archives of approaching 30,000 posts!


Nov 4 2003, 4:38 pm
Newsgroups: uk.d-i-y
From: Andy Hall <an...@hall.nospam>
Date: Tue, 04 Nov 2003 15:38:33 +0000
Local: Tues, Nov 4 2003 4:38 pm
Subject: Re: Adding inhibitor to CH system without draining
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On Tue, 04 Nov 2003 14:23:28 +0000, PoP <>

>On Tue, 04 Nov 2003 09:37:19 +0000, Andy Hall <an...@hall.nospam>

>>I doubt whether there would be any reaction between different brands
>>of chemical, but personally I would flush the lot and start again,
>>simply to have a known situation.

>I have the same thoughts on this.

>I know there is a recommended minimum level of inhibitor for a CH
>system, but is it feasible that there might be a maximum level? So if
>you've got inhibitor in there already and don't flush it out the
>system could overdose on inhibitor?

>Might sound implausible I suppose, but I expect heat transfer
>constants in water and in inhibitor to be different, so if you get the
>mix wrong.....


I'm not sure that overdosing (like double) with products like MB-1 is
a particular problem - Fernox recommend a 4% dosing but don't warn
about higher levels.

I did use some of their Alphi-11 product, which is a combined
antifreeze and inhibitor for my garage workshop circuit, which is
separate to the main house. While the pipework is well insulated, I
thought that there could be circumstances such as pump or other
failure where freezing could occur. With this product, there is a
maximum dosing level of 40%, which is good to -22 degrees, although I
used 30% which is good to -15 so a pretty safe bet.
ALphi-11 is glycol based and distinctly more viscous than water.

The circuit in question is sealed, and since this is a liquid product
rather than gel, it was necessary to come up with a means of delivery.
Fernox sells an injector product, which is, in effect, a modified
pumped garden sprayer. I bought a cheap sprayer from a DIY shed and
modified it with suitable pipework to have an adaptor to fit onto a
filling connection point. I was able to add the inhibitor (4
containers of it) quite easily this way and then added water to fill
and pressurise it in the same way. To begin with, the two liquids
didn't mix very well and there were circulation problems through the
radiators - one getting hot, the rest not. Judicious operating of
valves forced flow and mixing in the end, but it illustrates that
additives can have an effect. I've kept the injection machine in
case I have to do any work on the circuit. Since Alphi-11 is fairly
expensive, I can part drain the circuit into a large container and the
re-use the liquid. With some hard pumping, I can get 2 bar out of
the sprayer to pressurise the system.

Sep 25 2002, 6:21 pm
Newsgroups: uk.d-i-y
From: Andy Hall <>
Date: Wed, 25 Sep 2002 18:21:48 +0100
Local: Wed, Sep 25 2002 6:21 pm
Subject: Re: flushing out central heating systems
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On Wed, 25 Sep 2002 16:55:17 +0100, Roger <> wrote:
>richard newbery wrote:
>> Has any one used central heating flushing machines for their own heating
>> systems, are they effective, are they easy to use, do they pressure the
>> system to an extent that you have leaks forming after use. Do they
>> improve the efficiency of the system.

>If you have dual entry valves you need to take the rads outside and
>flush them individually. My system was "powerflushed" but BG decided to
>flush a couple of the rads individually, and LOTS of muck came out.

I think it's worth doing this anyway rather than powerflushing.

I recently did a system refurbishment and took radiators outside one
by one and hose them through with a pressure washer. While each was
off the wall, I flushed the pipes through gently with mains water.

Overall, this part of the job took me a couple of hours. There was
little in the way of rusty material since the system has been run with
inhibitor since new, although a little brownish water was flushed from
the radiators. From the pipework there were a few bits of old copper

After completion, refill with water, bleed air out and add corrosion



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