Refilling a Gravity Feed System

[Minchroadster]

Checked FAQ for refilling a CH system but appears to refer to a pressurized system.

Drained the CH system to refit a new TRV. Do I need to replace the existing olives on the pipe work or can I get away with fitting the new valve to the old pipe-work connections providing I don't over-tighten them?

Followed the instructions for draining the system - all good.

Refilling, simply the reverse? Open a few rads downstairs to help the system fill and push air out?

Any posts about refilling a gravity feed system anywhere, tried a search?

Mark

 

[gas4you]

if the olives and nuts are in good nick and the threads are the same, there is no reason not to use the old ones.

If you need to remove them you may have to carefully cut the olives with a junior hacksaw, don't go through to the copper pipe though.

 

[spongobongo]

I reused the old olives when replacing a check valve last week as it was impossible to get the old olive off without knackering the pipe. You might want to wind some PTFE tape around the olive first, just as a precaution. The ultimate test is that if it doesn't leak, the seal is good enough.

 

[bengasman]

As the name suggests, it works on gravity.
Just kidding although it is true for filling as well. Just undo what ever you did to stop the tank, and bleed the rads.
If there is an airlock, see faq

 

[Minchroadster]

Guys, TRV switched and replaced, system refilled with Sentinel 400 for a couple of days, old olives reused, no leaks or drips and the system is running fine!

Just staggered that the TRV which is no more than a 5 years old stopped working properly!

Thank you all for your advice and guidance - excellent!

 

[bengasman]

Gravity dhw system became obsolete about 50 years ago. Either installed very long time ago in the days that it was common, or a bit less long by someone who did not care to stay up to date.
Either way it is likely to have accumulated a vast amount of sludge, which is why your trv is failing. Good quality trv would be a bit more resistant than a cheapie, but none will keep working.
10 to 1 your system needs cleaning