Brivis Buffalo gas heater, pilot flame keeps going out

HI all,


I hope someone here can help me with a little dilemma I have been having with my old Brevis Buffalo gas heater. It's got a main valve, and from that attaches a thermocouple via a thin copper tube and a copper pilot tube to the pilot burner assembly tucked under where the main burners are.


It's been working fine for all these years, until only recently the pilot flame keeps going out. The flame eventually became very difficult to light where when the main valve is turned to PILOT, you would have to hold it down for some time before the pilot flame stays lit after letting go. After that, the main valve is turned to ON, and the heater would run and operate as per normal. The pilot flame would go out shortly after (3-4 days).


I replaced the thermocouple, and now it's extremely easy to light, however, I did notice that the pilot flame looked a little smaller/weaker than before. Normal operation of the heater resumed, but not for long, where the pilot flame went out (3-4 days).


In attempt to light the pilot again, and the flame was extremely weak while I kept the main valve depressed and would go out as soon as I released it. I also noticed at this time the thermocouple had a layer of soot over it. I found the orifice in the nozzle of the pilot flame was partially blocked with debris. With compressed air and alcohol, I cleaned the orifice out and the entire pilot burner assembly. This made the pilot flame very strong and blue with a tiny tinge of orange at the extremes. I thought I had fixed the problem, but it again lasted only 3-4 days before the pilot was out.


Upon disassembly again, I would find the same issue, the orifice was partially blocked. I cleaned it out again, and this time even cleaned out the 1/4" copper pilot tube (only 550mm length). The flame is again strong, but doesn't live longer than 3-4 days. It's always going out because of the nozzle being partially blocked with debris.


Further research suggested that the debris is from the inside of the copper pilot tube oxidizing blowing through. The inside of the copper pilot tube wall does look black. I replaced the entire pilot tube with a new flex-type in stainless (aluminium can have a similar problem too) and thought that would definitely fix the issue. It was great and better, and lasted more than 4 days, but after day 7-8, went out! Same issue, pilot hole for the flame was partially blocked.


Can anyone suggest where this debris is coming from that keeps clogging up the pilot flame gas orifice? Is there a filter anywhere in the gas supply prior and leading up to the nozzle for the pilot flame that may require cleaning out? Or is there something I'm doing wrong that has caused the debris to keep coming through internally from somewhere? Or if it coming from externally? I suspected the gas supply itself from the street being dirty also, however, I have other gas appliances (hot water cylinder, stove and oven) and they all don't have any issues.


Any help or ideas much appreciated before I get ask a gas fitter to have a look at everything I have done already to only be stuck like I am. Note that although it's fairly old, nothing else of the heater is broken or not working, no leaks in the heat exchangers or thermostat or fan motor burnt out or weird noises of any sort.


Kind regards,
David