Cylinder Leak at backnut

[verdigrey]

Hello Fellas , Some advice please . I fitted a new indirect cyl to a customers system about 3 months ago and it is now leaking very slowly from around the top coil fitting . Not the one I put on , but from behind the backnut around the thread . I have searched previouse posts and it mentioned both tightening the back nut or draining cyl , loosening backnut and putting ptfe around threads and retightening .
I did try tightening the backnut , but it didnt move . I dont know wether to drain the cyl and try resealing around the nut or just complain to where i got it from and they may send a new one out . If i did this they may say i overtightened the fitting and charge me for the replacement cyl .
any thoughts Guys .

 

[diamondgas]

If you get on ok with the merchants they may take it back. It may worth trying a repair first though, thing is once you do that they may then refuse to take it back. However you should be able to repair it. Been a while since I've done one but but I recollect using a pump washer and a boat load of PTFE. If you can't undo the back nut all the way then I'd be wrapping a load of PTF then overkill with LSK leak sealer... lol

 

[SafeGasInstall]

as above +

drain down heating and repair should be easy if you did not kill the fitting on install day by over doing it

and you have position cylinder that flow return is easy to access

 

[dontknowitall]

Out of interest, which make of cylinder?

 

[verdigrey]

Thanks Diamondgas , and SafeGas , As the access is not too difficult I will drain down and see if the backnut will undo and if it does I will reaseal it .
Dontknowitall , It is an RM cylinder 900 x 450 . are they prone to it ?
Just wondering if anyone has been around a cylinder factory , it must be quite interesting .
Thanks again .

 

[dontknowitall]

Thank you, Verdigrey.

I've had trouble with two of these (the third installed without a problem).

They were twin coils and I was told that vibration during transit often causes a problem.

 

[stevetheplumber]

drai it slacken the back nut just enough to get ptfe behind half a doozen turns and retighten obviously yoeed to hold the treaded part to stop it twisting
ive done a few like this that were old so hopefully it will be easier and more likley succesfull on a recent cylinder id be tempted to try nipping it up a bit live, before going down this route as hopefully the internal washer is still in good condition

 

[verdigrey]

Thanks Dontknow itall and Steve , I will try resealing . Cheers .