Combi-boiler fill-loop - identifying it ...

Today, I removed a radiator to do some decorating - usual thing, closeed both radiator valves, drained it, re-connected it. Now, of course the CH sealed system pressure is 0 and I need to correct this with the fill-loop. However, I've not exactly sure where it is ... I know that by law, the loop shoudl be disconnected, and it is - the flexible pipe is lying on the floor of the boiler cupboard. I'm just not exactly where it should be connected ... There is a red bulbous small tank with a pressure gauge on it (reading 0 ...) which has a spare valve coming off it and a rising pipe that goes nowhere quite close to it with a valve on the end. It looks a lot to me like the flexible pipe has to connect these two things because I can't see anywhere else it could go. Any advice?
PK
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On 29 Nov 2003 10:02:24 -0800, snipped-for-privacy@kime.org.uk (Philip Kime) wrote:

This is the expansion vessel.

Connect the flexible pipe to the valve on the end of the rising pipe, direct it over a bucket and try opening the valve very carefully. It should have mains cold water behind it. Run a little off to clear any crap in the pipe. If it doesn't have mains cold water, then you need a source of it such as the cold feed to a washing machine.
The fittings are supposed to be close enough together to connect via the flexible hose. If not, a way round it is to buy a washing machine water hose from a DIY store and use that instead.
Again connect the hose to the water supply and open the valve to fill the hose, then connect it to the valve at the expansion vessel.
Now you can fill and pressurise the system by opening the mains valve followed by the valve at the expansion vessel. Fill the system until the gauge reads about 1.5 bar and turn the water off. Go round and bleed the radiators. Add more water again up to 1.5 bar and bleed any remaining radiators. You may need to do this a few times until all water is eliminated and the pressure is at 1.5 bar or so.
Then disconnect the filling hose.
However.........
Before doing this, add some inhibitor to the system. If you don't have a separate point for adding inhibitor (and in most professionally installed systems the installer doesn't bother), you can introduce inhibitor through a radiator vent. THere are two approaches.
a) Use a liquid like Fernox MB-1 and some fine plastic tube that will fit through the vent hole. Go to an upstairs radiator and add by siphoning into what should be a nearly empty system.
b) Use a gel like Fernox Superconcentrate. This costs a little more than the liquid but is convenient. This comes as a cartridge for a mastic gun plus a short tube and adaptor for the radiator vent. You connect up and squirt the stuff in. The instructions cover how to do this in an already pressurised system. This can be messy if the adaptor doesn't fit well so I never use it. It is much easier to just fill the empty radiator and then add the water.
Do use an inhibitor though. THe system and especially radiator lifetimes will be considerably enhanced. The inhibitor concentration can be tested once a year and more should be added as required.
.andy
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