Back boiler plumbing

[badgerbag]

Hi,

 I’m about to put in the connections on a solid fuel back boiler. It’s a few years since I did much plumbing so I’m wondering what the best threaded joint sealer is. I always used Boss White or PTFE tape, but I see there is now liquid PTFE and several silicone concoctions available.  Has anyone any recommendations?

cheers!

[Ex Brummie]

PTFE would be up to the job, but if you do decide on any of the 'plastic' solution sealants, be sure to check the temperature ratings. Those fittings on a stove boiler can get very hot.

[BEngo]

Tru Blu works well, but requires 24 h to set before it can be used. Heldite is also good, but, like Boss White and hemp sets very hard.

 

I would stick to ptfe tape, in the interests of dismantlability.  The gas rated stuff is a bit thicker which can be handy if both the threads are parallel.

 

 

[jonesthenuke]

PTFE tape is awful stuff. I would use boss white and hemp.

[Ex Brummie]

15 hours ago, jonesthenuke said:

PTFE tape is awful stuff. I would use boss white and hemp.

Until it gets baked on this type of joint, and the potential for vibration causes cracks and the hemp fibres actas wicks.

I would also use more wraps of standard PTFE rather than the gas type .

[Ronaldo47]

Hawk Red type A or B are good for high temperatures (600°C ), but are not cheap, and are not suitable for potable water pipework.  It pays to shop around: my 60-year-old tin of type B has gone hard, and I was  searching on line for some a few minutes ago. Prices asked varied from around £25 to more than £120 for the same size of tin. 

[ditchcrawler]

If his boiler gets to 600° he will be in trouble. All this high performance are we talking about a super heated steam system  or a didely back boiler and a couple of rads at atmospheric pressure 

[blackrose]

21 hours ago, jonesthenuke said:

PTFE tape is awful stuff. I would use boss white and hemp.

 

Gas PTFE tape in the yellow rolls is good stuff. Never had a problem with it. You just have to remember to wind it in the male thread direction so the female doesn't take it off.

Edited October 3, 2025 by blackrose