Still not getting hot radiators

[Dan Robinson]

pressure washer

 

[Dan Robinson]

I think the key is in that shiny gate valve under the mid position valve.


But honestly I can't look at that picture for to long before the urge to inflict actual harm to an human becomes worryingly strong.

 

[StudWall]

Hells yeah,

Point it in one end and shoot the black crap out the other. They were solid old single panels though, wouldn't try it on these modern flimsy ones,

Afterwards you could see through to the other side and none of them leaked

 

[Dan Robinson]

Thing is you only cleared the initial blockage. . The flow rate on a pressure washer is far too low to clear the build up elsewhere.

Further work will be, required.

 

[dominoman]

I think the key is in that shiny gate valve under the mid position valve.


But honestly I can't look at that picture for to long before the urge to inflict actual harm to an human becomes worryingly strong.

Yes. I know. It's not good. Unfortunately our surveyor didn't open that airing cupboard as the seller had "lost the key"

When we eventually completed we opened it and it was full of water. That gate valve is a new replacement (but it is fully open so can't be causing the problem).

I just did the magnet test and the magnet sticks to the hot water pipes and even more strongly to the air separator. Should i cut out and replace the air separator next? Or is it going to need a powerflush anyway if the magnet is sticking to the pipes?

 

[StudWall]

Yes I only cleared the blockage but in the end it solved the problem.

I would be cautious paying for a power flush, yes It'll get some crap out but a lot will still remain, just as much as a manual flush, But it's upto you

 

[St0rmer66]

I had a system the other day with a blocked cold feed/open vent area... 13 of the 15 rads got "warm" (not hot) and the boiler cycled a lot. Draining radiators at first it was crystal clear and I was starting to doubt my diagnosis but when I cut it out the pipes... Wow. Barely a pinhole left for the water to flow through. Cleaned it out, pump valve was also full of crap (I was changing the pump anyway since it was knocking), put a magnabooster filter on and away it went. Customer said it was better than it had ever been in the last 10 years! I combined the cold feed and open vent in this case but you shouldn't need to in theory having an air separator.

 

[dominoman]

I had a system the other day with a blocked cold feed/open vent area... 13 of the 15 rads got "warm" (not hot) and the boiler cycled a lot. Draining radiators at first it was crystal clear and I was starting to doubt my diagnosis but when I cut it out the pipes... Wow. Barely a pinhole left for the water to flow through. Cleaned it out, pump valve was also full of crap (I was changing the pump anyway since it was knocking), put a magnabooster filter on and away it went. Customer said it was better than it had ever been in the last 10 years! I combined the cold feed and open vent in this case but you shouldn't need to in theory having an air separator.

Thanks. That gives me hope... I had the same when I first drained the system. Crystal clear, which at first gave me hope. But now I think it's just because there was too little circulation to kick up the gunk.

Which pipes did you cut out? Just around the water inlet, or in other places too? And when you cut out do you clean and put back - or you put new pipe in? Thanks

 

[St0rmer66]

Cut out the whole air separator. Cut it where it's most convenient to put a joint back in because you can just clean the pipes out and put them back with compression fittings (easier if it ever needs to come back out). Where the cold feed meets the system is usually the worst place.

 

[dominoman]

Thanks. Is it worth doing this before getting a Powerflush? I expect other pipes are blocked too.

So I would cut out the air separator and the cold feed as marked in pink below?

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• dominoman
• 9 Dec 2014
• 1

And then also this central heating hot feed pipe was magnetic when i tested it last night, so I think also might be blocked. Is this also worth cutting out at the same time?

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• dominoman
• 9 Dec 2014
• 1

If I cut that out I could replace the pipe with a simple straight run across from the pump exit (and refit the air pressure valve too).

 

[StudWall]

If some of your radiators are getting hot then that tells you that there must be sufficient flow to make them work all around that piping.

There may be insufficient to heat all the radiators but by turning the hot ones off you are diverting that flow to the cold ones. the fact that they still don't heat properly tells you the problem lies with a blockage between the tee-off to them and where they re-join.

The fact that the cold ones are downstairs is a classic case of sludge build up as the sediment settles at the lowest point. Try taking one off and flushing it, that will give you an answer. If you don't want to do that for whatever reason then power flush might be your only optipn

 

[St0rmer66]

Where you can just undo existing compression joints, the less cuts you need to do the better! Yes that's the air separator in pink. Obviously cut above the soldered coupling above it and leave about an inch of bare pipe if you have room (it's more than you need for a compression but I prefer to have plenty). I expect the CH pipe will only have a minor amount of magnetite but if you're drained down anyway then why not? Don't put an auto air vent back on, replace with a manual vent on an open system (they can suck air in due to the lower pressure compared to a sealed system).

 

[dominoman]

If some of your radiators are getting hot then that tells you that there must be sufficient flow to make them work all around that piping.

There may be insufficient to heat all the radiators but by turning the hot ones off you are diverting that flow to the cold ones. the fact that they still don't heat properly tells you the problem lies with a blockage between the tee-off to them and where they re-join.

The fact that the cold ones are downstairs is a classic case of sludge build up as the sediment settles at the lowest point. Try taking one off and flushing it, that will give you an answer. If you don't want to do that for whatever reason then power flush might be your only optipn

Thanks. Yes - you are right. There must be enough flow around there because some radiators get really nice and hot. But downstairs are lukewarm or totally cold.

I did try taking one radiator of the wall downstairs but never again! It is cast iron and weighed more than the sun. Still, while it was lying on the ground I checked and water flowed from both valves at good pressure when opened. I also attached a hose to the radiator and water came out easily and was fairly clear. But as soon as I reattached it all there is no heat going to the radiator.

 

[StudWall]

Strange that the water in the radiator was clear, I would have expected some gunk, even in fairly new ones.

Try following the pipes and finding where they tee off to the downstairs, maybe tapping the pipes with a soft hammer will help loosen the blockage

 

[dominoman]

Where you can just undo existing compression joints, the less cuts you need to do the better! Yes that's the air separator in pink. Obviously cut above the soldered coupling above it and leave about an inch of bare pipe if you have room (it's more than you need for a compression but I prefer to have plenty). I expect the CH pipe will only have a minor amount of magnetite but if you're drained down anyway then why not? Don't put an auto air vent back on, replace with a manual vent on an open system (they can suck air in due to the lower pressure compared to a sealed system).

Thanks. I'll do that. I should be able to get away with two cuts for that separator, and then I can try and clean it properly. I'll also take out the pump at the same time and see if I can spot and gunk inside it.

Sorry to ask - but could you explain what a manual vent looks like - or post a link to one so I know what to look for? Many thanks!