We’ve just had our system flushed and filled, and I can tell you, it’s not an easy or quick job to get right, so I can see why installers cut corners. There are various power-flushing methods and bits of kit you can buy, but in our case, the goal wasn’t so much cleaning the system as it was getting rid of trapped air.

The fill and flush valve we had installed worked brilliantly. It does need to be plumbed in… it then has one end that connects to a pipe leading outside, the other to a mains water supply. If you’ve got good mains pressure, you’re in luck. We only have about 1.5 bar here, but it was still good enough, and honestly, it was shocking how much muck we pumped out.

If you go down this route, I’d recommend fitting the valve and purging your system for an hour or two. Then add some system cleaner, let it circulate for a few days, and repeat the flush. You’ll be amazed at what comes out.

The fill and flush valve setup can be seen at the 3:42 mark in this video:

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There are loads of other ways to approach this, but once the valve is fitted that we used, this is something most DIY-minded homeowners could easily manage themselves.

Posted by: @grantmethestrength

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Well the hits keep coming! I had a sudden loss of flow from 28 l/min to barely nothing so had the installers back in. I genuinely don’t believe that they flushed the system when it was installed in Jan.

FWIW my flow crashed when I started my system up in July to attempt cooling for the first time, the space heating part of it having sat around doing nothing for a couple of months.  I didn't realise however that this had happened because I wasn't, at the time, monitoring flow.  Also I had flushed the mag filter which had very little in it, so assumed that there was no possibility of blockage.  This didn't fix the problem!

There were all sorts of seemingly disconnected error messages that had me worried.  So installer turns up, spends 5mins looking at the control box, goes straight to the filter like the one illustrated above and flushes it out.  Pitch black, service fully restored.  He remarked that 90% of callouts are the mesh filter (which I didn't even know was present.   I get the impression it might be a regular maintenance item, obviously its a much finer filter than is historically fitted to boilers which is of course a good thing!

I know he flushed my system (which does have old pipes and some old rads) well when he fitted the ASHP, so I guess this may be par for the course.  It doesnt actually take much grot to block a small fine filter!

Sorry I cant comment on the diverter valve.

@editor Yeah I watched the episode and am probably going to swap out my inatec flow regulator as it looks like crap an yes it is less than a year old allegedly!

I like the idea of being able to easily flush the system. The earliest I can get a plumber out to flush the system is end of Jan and it will be quite expensive I have decided to upskill myself to sort out my own system!

@grantmethestrength I applaud your ambition on the need to take back control. And as can be seen by the many cases of blockages, it’s very much a regular occurrence especially on recently installed systems. 
We had the same after 18 months.

Key cause in our case - suspected system not flushed and insufficient system protector additive.

I started to notice a variable flow rate each time the flow rate enquiry was requested. In other words it wasn’t a full blown fault code at the time. Nonetheless there was a problem.

I isolated the mag filter dismantled and fully cleaned out the chamber and reassembled it. While you can flush the mag filter there can be mistakes and some sludge can still get back into the circuit.

secondly the ‘return pipe’ gauze filter in the isolation valve was inspected and ironically it was fairly clear. So it became a bit of a puzzle as to what was blocking the flow. 

I decided to reverse flush the HP heat exchanger by removing the gauze filter, unscrewing the ‘return pipe’ filter nut and opening the valve - bringing water back through the Heat Exchanger at about 1 bar mains pressure. This also meant it wasn’t a full drain down.

The result was a mass of scale and fine particles. see pic below.

This was a short jet flush with only about 6 ltrs removed but has completely removed the problem.

I then decided to do new calcs on the volume of our system and ensured that 11/2 bottles of Fernox was added as I seem to recall the original installer did not top up after some remedial work.

I’d only say that knowledge of the system components and flow directions need to be fully understood to undertake this kind of remedial work.

I also bought the filter seen in Mars’ video about a year ago. Which since all is working I haven’t fitted yet. 

@sunandair it is a case of necessity as soon as you mention you have an ASHP most local plumbers run a mile and being rural that means no plumbers for Simon! I have pretty much labelled up all the pipe work so am happy how it is piped. That alongside my PhD masters in plumbing shenanigans from youtube university I reckon I should be ok! Hey whats the worst that could happen!!!!!?????

@grantmethestrength with your pragmatic approach and 👀 knowledge on hand I’m sure it will be a positive outcome. Don’t hesitate to ask if any questions crop up along the way. Best of luck 👍