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Flushing of a condensing gas central heating system

Postby frankino » Wed May 26, 2010 3:47 pm

Is it a complex task to carry out the flushing and refill of a condensing gas central heating system with an inhibitor to prevent corrosion as I don't think there was any in the system in the first place?
The system is about 2. 1/2 years old. Make Alpha CD50.
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Simply Build It

Postby plumbbob » Fri May 28, 2010 10:36 am

The principle of draining and re-filling a system whether it be a sealed or open system (you don't say which) is simple.

The overall difficulty however depends on several factors. A thorough flush requires specialist equipment but in most instances a simple drain down will be sufficient to remove debris. If you suspect inhibitor has not been added or worse, the system was never flushed after the install, it may benefit from more than a simple drain down. Have you checked the boiler handbook? Your installer should have completed the record section with all the relevant details and details of any treatment should be shown.

Re-filling ought to be simple too, but sometimes trapped air can be awkward to expel.
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Postby htg engineer » Sat May 29, 2010 6:24 pm

If it's pressurised then airlocks/air wont be a problem.

You wont know what you need to do, until you drain the system, and check the condition of the water.

I would advise, draining, removing all radiators and flushing through with hosepipe. Turn off all radiator valves, open/connect filling loop (not fully, as it will fill too quick and operate PRV) - open each valve one by one and allow to flow into a bucket or down a hosepipe.

If the water is clear refill and add inhibitor - such as Sentinel X100.

If the water is still dis-coloured I would add a system cleanser. And repeat above process after a few days.

Bearing in my you nearly always get abit dis-colouration of the water.

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