B
big_al
Hi, I've got a very old Glow-worm 92/100 boiler which is gravity fed indirect (it must be 30-40 years old. Having had a leak from an old galvenised F&E tank for a year finally got around to replacing it (and not a moment too soon as it had gone literally paper thin). Refilled primary and no HW but CH working ok - heat soak radiator in bathroom (no TRV) got hot but pipes up to cylinder didn't so gravity not working. Thought either airlock or blockage as there was a bit of sludge went down the fill pipe when draining the F&E tank. Tried draining and refilling slowly and bled rads as it filled. Still no improvement, same as before. Tried connecting rising mains (5 bar) to hot water vent and water welled up into F&E tank. Tried connecting rising mains to cold fill pipe in F&E tank and water came out of hot vent into F&E tank. Tried alternating above a few times (attempt at sort of home flushing). The above rising mains flush was doen with system full and drain tap next to boiler closed. Got impression that amount of water going in was more than coming out into F&E so was hoping might have got rid of air lock and it had filled up a bit more. Fired up and now I've still got CH working but no HW. However, the HW return at boiler gets hot and HW feed at boiler remains cold - the soak radiator in bathroom appears to get hot but from the return side now rather than the feed (Up until a week ago it was the other way around). I think I might have got a blockage further down the HW gravity system (possibly in the boiler or between boiler and soak radiator?) Boiler thermostat appears to be working ok and cutting boiler out at certain temperature. Don't want to boil system due to age. Don't want to spend a lot of money as everything is due to be completely replaced in a few months (boiler, tanks, rads, and pipework).
Probably should mention that there is no cylinder stat (just what looks like a pressure regulator valve on flow input to cylinder), only CH has a pump and there are 4 pipes to boiler (2 for HW and 2 for CH). Can't see any other valves in the system.
I know these airlock/blockage problems can be buggers to sort. Any ideas? Is it worth trying a flushing chemical, trying the rising mains again on hot vent and/or F&E cold water fill at same time with drain tap next to boiler open, or even with whole system drained down first....?
Probably should mention that there is no cylinder stat (just what looks like a pressure regulator valve on flow input to cylinder), only CH has a pump and there are 4 pipes to boiler (2 for HW and 2 for CH). Can't see any other valves in the system.
I know these airlock/blockage problems can be buggers to sort. Any ideas? Is it worth trying a flushing chemical, trying the rising mains again on hot vent and/or F&E cold water fill at same time with drain tap next to boiler open, or even with whole system drained down first....?
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