Leaking HW Cylinder Flange

[BoutTime]

Hi All,
I have a leak coming from the Heating Coil flange on our HW Cylinder. Long story short if I replace the Cylinder which is 25 years old I may as well go unvented and replace the boiler and power showers (not compatible with mains pressure water) also. The costs are obviously significant. It has been recommended that CT1 might work as a temporary measure to get the HW back online and allow for some time to consider options. I also already have some LS-X. Has anyone had any success sealing an external leak like this? Many thanks.

Video of Leak

 

[blup]

Good old fashioned hemp and boss white

 

[BoutTime]

Good old fashioned hemp and boss white

Thanks. Very useful but my fear is the cylinder will be weak and trying to undo the nut will wreck the cylinder and leave me with no heating.

 

[blup]

Try any of the proprietary leak sealers or ….it’s time for a new cylinder

 

[Madrab]

It has been recommended that CT1 might work as a temporary measure

Nope, never found any kind of sealant to work when trying to seal water systems. Is it the actual tapping in the cylinder or the compression fitting that's at fault?

 

[BoutTime]

Nope, never found any kind of sealant to work when trying to seal water systems. Is it the actual tapping in the cylinder or the compression fitting that's at fault?

Cheers. The tapping in the cylinder I think. Water seeps from the base between the flange and the cylinder. Similar to what's show in the YouTube video linked above.

 

[ChrisJP]

You'll never get a seal while water is actually leaking out of the flange.
The only thing that might work is to drain the cylinder completely, then use heat to completely dry the flange and its surroundings. Then apply the sealant generously around the flange, forcing it into the gap between flange and cylinder. Then allow it to set thoroughly before refilling the cylinder. Then keep everything crossed that the leak doesn't restart!

 

[Daveydub]

The video above shows what I would do and I have had quite a few successes and no failures.
You could also replace the cylinder with unvented but run it as vented off your existing feed & vent arrangement so showers could remain.
Changing to an unvented cylinder does not mean that you need to change the boiler, that can remain as open vented whether cylinder is mains fed or open vent.

 

[dilalio]

Did one recently.
Drain cylinder and central heating.
Dismantle pipework and flange - cylinder coil will sway about when loose.
Clean all threads.
Make a washer out of ptfe and paste it up.
Reassemble and don't over tighten.
Fill back up and give an extra nip if required.

Worked fine for me. Did warn customer though.