Feeder Tank Wont Empty

[muppet6556]

I have been having a problem with my CH. Water is ok(slightly lower temp than normal perhaps) but the rads are all cold. Pump is new, control system is new, thermos are new and all have worked well previously. Figured it was sludge so drained the system off. All the rads are empty but the feeder tank in the loft is still as full as it was. Is it a sludge blockage in the pipe and if so whats the best way to fix it.
It is a standard Sundial Y plan system with 3 upstairs rads and 2 downstairs.

 

[hi-spec plumbing heating]

that problem is common blockage most occures where feed pipe from tank joins main system.
use a chemical to remove sludge or cut that section of pipe out and renew.
sometimes pressure from a main pipe can shift it.

 

[muppet6556]

Thanks for the quick reply. I got a bottle of Sentinel x400 sludge remover from B&Q. Should I just pour it into the tank and wait?

 

[JohnD]

no

if the blockage is preventing water flowing down from the F&E then it will prevent the chemical from flowing down there too.

you can probably fill the system up from the bottom by putting a hose on the drain cock and filling until it comes out of the vent. this will at least allow you to have heat. if you can put the chemical into a system, e.g. by taking out a radiator bleed valve plug, before refilling, it will circulate round and there is a change it will be able to attack the blockage.

it is likely that you will have to cut out the Tee where the 15mm F&E pipe joins the circulating pipes though, and poke out the blockage or replace the blocked pipes. You will have to do a chemical clean afterwards or lumps of sediment will circulate and cause another blockage or damage the pump.

If you can afford £100 for a Magnaclean it will trap the sediment loosened by the chemical, and will continue trapping sediment indefinitely.