Bottom of rads cold

[Jaybee 45]

Hello, the bottom of my radiators stay cold although the top is hot. I've tried bleeding them but no air is coming out only black water. They are heated with a combi boiler. If this could be a case of sludge how would I flush the system out with the chemical. Where would I put it as I dont think there is an expansion cistern.( whatever that is ) We also have noticed for a long time black bits around the shower head and also on the cold tap in the shower room. But nothing on the hot taps.

 

[JohnD]

it is possible to inject it through a bleed vent hole

however, you will want to drain and flush the system out with fresh water first, and you will find it easier to add the chemical while the rads are empty before you refill it.

it will be very helpful to fit a Magnaclean device as well, which will capture and retain circulating black sludge (you will never clean it perfectly),

have you got drain valves, and are you willing to do some pipe cutting and fitting?

do all the radiators attach to pipes coming out of the floor or along the skirting, or do any of them drop down from the celing?

 

[hi-spec plumbing heating]

drain a rad or system and remove the complete bleed valve fitting on rad and place through hole and reill rad/system.

or you can buy the attachments from a plumbers merchant to inject it into system.

 

[JohnD]

hee hee!

 

[hi-spec plumbing heating]

8)

 

[Jaybee 45]

Hi All the rads have drainage valves. Some of the pipes come down from the third floor. The house is 7 years old. I think this might be a bit ambitious for me to attempt. Is it an expensive job for a plumber to do? We have 13 radiators. The boiler is an Ariston Genus 30. I have just looked and the bar is just past 3 going into the red. Is this anything to be worried about?? Appreciate you help. Thanks.

 

[hi-spec plumbing heating]

not a good sign, but the prv should activate above 3 bar

 

[JohnD]

If you have a plumber do the clean, he will probably want to use a powerflushing machine, which drives the water and chemicals round with great force. This makes the job quicker than if you did it yourself, but it will cost some hundreds of pounds.

If you are having a plumber in, get him to fit a Magnaclean for you. This is the only job that requires cutting and jointing the pipes. The device costs about £100 but you will be surprised and gratified by how much sludge it captures, even after flushing. If you have this done, and have plenty of drain valves, I think you will be able to do the chemical clean and rinse yourself. It will probably take you a matter of minutes to introduce the chemical (since you can add it through the Magnaclean) and it will probably take you a Sunday to drain and refill it after a couple of weeks, when you can add an anti-corrosion inhibitor in the same way. As you have radiators fed on drop-loop pipes you will have to drain each of them, which will take extra time but is not complicated. The Magnaclean will carry on working indefinitely, and you can open it to remove the accumulated sediment from time to time (no plumbing skills required).

p.s. make sure the filling loop is turned off and disconnected, to prevent mains water pressure geting in to the boiler.

 

[Jaybee 45]

Hi JohnD, Thanks so much for your valuable information. Very much appreciated.

 

[Jaybee 45]

I was just about to send for Magnaclean but noticed that it is for 22mm pipes. How would I measure the size of my pipes. The pipes to my radiators look very narrow.

 

[JohnD]

each radiator is probably fed by a 15mm pipe (maybe smaller - if they are the thickness of a pencil they could be microbore

however, nearer the boiler, several of these thin pipes will be fed from a thick one - firstly 22mm, then maybe 28mm. Magnacleans are also available to fit 28mm pipe, not sure if that one is more expensive.

Hold a ruler or tape measure behind the pipes. the 22mm is the external diameter

You can get converters from 28m to 22mm but it would not be a good idea to fit it on a 15mm or microbore pipe.

If you can post some pics of the pipes round your boiler and round your hot water cylinder we may see a suitable place. Maybe near the pump and 3-way valve. The Magnaclean is big enough to be unsightly if not in the airing cupboard or by the boiler.

If you or any of your friends or neighbours know a good plumber I am sure he could fit it for you at a reasonable price, but it is not a complex DIY plumbing job.

p.s. it ought to be fitted on the return pipe to the boiler, then it will catch sediment on its way to the boiler. If fitted anywhere else it will still eventually trap all the circulating sediment, though.

 

[oakland99]

i've only just read this thread but i would advise a bit of thought before you just add a magnaclean,,,these are very good, but how bad is your system..if you have many rads that have large cold spots then its best to get the sludge removed first...this is a longish job to do properly you will need to use a powerflush machine or remove each rad and flush out with a hose, once system is clean then fit magnaclean this will then stop any loose debris clogging your combi. agree with plumber whats going to be done before paying.

 

[JohnD]

7 years old and a Combi....

wouldn't expect it to be too bad, and if the water is still circulating, it will work.

I did my old mum's 30-year old dirty system with a Magnaclan and a litre of X400, was very pleased with the results (and saved a few hundred pounds on a powerflush too)

 

[oakland99]

yeah if the sludge isn't to bad i agree x400 will do the job, but if its quite bad you may need to powerflush all depends how much sludge is in the rads, i've seen many when over 50% or the rad was cold caused by sludge but as its 7 years old your right it shouldnt be too bad
i didnt read that bit where it said the house was 7 years old

 

[Jaybee 45]

Thanks for the replies. I am having a plumber to check if I need a power flush first before having the magnaclean fitted. ( someone my husband knows). As you said JohnD the pipes to the rads are 15mm but they are 22mm near the boiler. Not all the rads are affected about six are and it is mainly at the bottom centre where the cold spot is about 20% of the rad. The tops still get really hot..... Appreciate your help PS. The boiler is in the integral garage so it wont matter if the magnaclean shows.