[Closed] Central heating issue

Swarf coming away from the inside of a copper joint
Potentially new rad didnt get more inhibitor added and there has been some rust or oxidation
Not sure what else it could be that 2 x pros couldnt solve
You have tried turning up the pump to #3?
I would hook a hose pipe up to the furthest cold rad, disconbect the ch 22mm return and wind up the flow but then i am tight when it comes to spending money till i have tried all i can do by my self

Thank you STM. I guess it probably doesn’t take much to restrict a pipe, it’s weird that the issue didn’t appear until a while after the new road though. I haven’t put my hand in my pocket yet.. the installer has been very good about things. I do need to have a conversation though about this power flush work. I guess that’s the same principle as your hosepipe idea? TBH I’ll try most things myself but central heating, gas and electrics are my no-go areas.

Edit - When you say turn up the pump to #3 do you mean isolate the coldest rad and turn the heating on with it maxed out on boiler? (It’s already on 5 out of 6)

Thanks

I've had plastic pipework completely choke up with sludge before. Were the radiators existing before the new boiler or were they cheap radiators? That has been the cause when I've had the problem.

Can you access the pipework supplying these radiators?

I'd be looking at that first. If it is blocked a power flush won't shift it from my experience.

Thanks Bear. The rads were all brand new, don’t really know if they were cheap or not as it was 1 price for the whole install. The Worcester Bosch engineer commented how clean the water was from the system - it looked like it was straight out the tap and the filter was squeaky clean too. Would any sludge show itself in dirty water elsewhere in the system?

As for access, two rooms are okay as they’re carpets and floorboards. The third room is a tiled bathroom.. 😐

Some WB combi do habe a vari speed pump on the ch circuit.
Pop the cover, look for a round coffee cup sized thing with a silver middle and a screwdriver slot in it
Further in than that is the pump power module, on the side is a selector lever. Low middle and high, whack it up to 3.
Could yoou pop the middle rad out? Then undo the outlet from the firdt one and the input tp the next thus effectively giving undrestricted flow left snd right. Some placcy pipe and a funnel will tell you if its blocked, you sjould be able to blow the ch water through ad its only going yo be a 20cm lift or so. That would give you more info, and help dial down the problem

If water and filter are clean then probably rule that out.

the pipe could have collapsed or kinked somewhere especially if plastic and it has been formed in a tight bend.

If affecting 3 radiators I would be looking at some common pipework. You could be unlucky and have 3 valves fail at same time but unlikely, and I assume they have looked for obvious.

Re-reading your initial post it would seem linked to a extra rad installation, I would be examining that to check some pipework hasn't been bypassed.

Not sucking air in is it, I had this once , engineer told me that it was usually bathrooms for some reason. Any way I had to bleed one radiator regularly while we lived there if I wanted heat in that bedroom, just turn pumps off while you do it or it sucks more air in like buggery.

the pipe could have collapsed or kinked somewhere especially if plastic and it has been formed in a tight bend.

I'm leaning towards this: pipe kinking just enough when hot, especially as the radiators work when the systems been drained and refilled, i.e. is running from cold. Maybe a tight bend, maybe sub-par plastic pipe. I've seen stranger things.

Do you know where the new pipe actually runs and could you work out where it curves the tightest?

Are any of the pipes getting hot as you work your way round the pipe circuit?

If not the pump is dead heading which means there is a restriction. The restriction is more likely to be on the return as if it was on the flow the water would just head through a rad and back on to the return so only up to say the 3rd rad got hot that would give an idea of where a flow restriction is.

So if the pipe work is not getting hot my bet is on a restriction in the return flow.

To check boiler you (or the plumber ) could always plumb in a mock one rad circuit with a valve in line that can be used to simulate the pressure drop over the entire cuicuit. Gate and ball valves are highly nonlinear but should still be able to experiment and give some form of additional restrictions to create a reasonable test for the boiler.

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I would have thought that the pump speed would be the first thing checked by the various people who've visited.

Pump speed on a combi boiler shouldn't, in general, be adjusted.

Thank you for the responses all. I'm not going to fiddle with the boiler given it's had a good going over by the pros on more than one occasion (there were laptops involved..).

I think there must be a physical restriction somewhere so I'm going to start lifting carpets and boards tonight in the easier places to access. I know exactly where the CH pipes come upstairs and then start branching off to the various rooms so that will be where I'll start. Then it's a case of lifting the carpet where the new rad is and seeing what's what. Next step after that is to pull the bath panel to see if I can inspect the bathroom radiator without disturbing the tiled floor first.

Thanks

Update. Having looked into the power flush process I'm not confident it is going to resolve the issue and I'm leaning towards just putting the money/effort of doing that towards ripping up floors and replacing pipework..

As noted earlier in the thread this is not too much of a mission other than the bathroom. Does anyone have experience of ripping up porcelain tiles from a floor without disturbing wall tiles? All walls are tiled and I'm worried ripping up the floor may disturb them.. Any advice on how to do this safely would be most welcome.

The area of flooring is small so the cost of the tiles, adhesive, grout, etc. is low and I'd be doing the tiling (again). It's just going to be a king size pain in the arse as this is our only bathroom in the house and I'll have to work at pace!

De-pressurise the system.

Disconnect the supply side of each (non working) radiator in turn and get an assistant to carefully open the tap on the filling loop.

If pressure in the system rises then you can narrow down the restriction. If water flows freely it's an issue with the installation.

Pro: this might actually clear the blockage in the pipe if there's one there.

Con: no matter how carefully you do this water will escape. Plenty of old towels needed.

Thanks Flaperon. I'm waiting for the plumber (who installed the system) to call me back about next steps so I will discuss this with them. I feel like the powerflush is more for sludge/grime build up (of which there should be almost none) rather than a physical blockage and it'll be a waste of time/money.
Cheers

no matter how carefully you do this water will escape. Plenty of old towels needed.

Put a 15mm compression nut onto one end of an offcut of 15mm copper pipe, screw in a straight coupler and you'll be able to screw onto the radiator feed. A bit of hose pipe will fit over the open-ended copper and you can route this to a bucket/sink/bath as required. No mess.

Thank you, that makes sense. My wife will be happy if there’s less mess.. especially as there’s newish carpets in two of the rooms!
Cheers

Is the bathroom upstairs? Accessing pipe work from below is sometimes an easier option, i.e. through the ceiling. Easier to replace a bit of plasterboard and make good than disturb tiles, skirting boards etc.

Very good point! I hadn’t thought of that, bathroom is directly above downstairs WC with the same foot print so that should work. Thanks

Can you get a spy camera for your phone
Some are really good and can be directed around by bending and mamipulting the cabling. Might t get away with drilling a couple of holes in a floorboard as opposed to pulling the lot up
Or pop the rads one at a time and check flow / returns
There musr be a logic gate thingy test to eork out thr minimum steps required to give a positive outcome, but im a simpleton so its beyond me