Hot water cylinder, slight leak...

[HarvestMoon4]

My mother has a hot water cylinder in her airing cupboard, it has a slight leak coming from the nut, right on the bottom of the cylinder (Should have taken a photo I guess...) I have tightened it slightly, it was ok for a few days but it has started to leak again, not a lot, but enough to leave a small puddle on a saucer.

I understand that one has to be careful about tightening too tight. OK, do you think I should undo the nut and check if the washer has worn (If there is one?) should I use plumbers mate and just wrap around the threads, if the washer seems to be ok?
By the way it's not a new cylinder, it's not old and rusty either.

Ops just an after thought.... A tank full of water, will have to be emptied right?

Many thanks

 

[Burnerman]

The lowest pipe is the cold water feed into the cylinder from the tank in the loft.....don't overtighten, you dont want to shear or distort the male thread that comes out of the tank!
Ideally, drain down, undo the nut thats leaking, wrap ptfe tape around the olive, add some sealant for good measure and reassemble.
John

 

[JohnD]

PTFE tape is great!

it is also very suitable for sealing threaded conections (it does not need to go on the threads of a compression fitting, where the olive makes the seal, but it helps the olive.)

If it is a rather old copper cylinder, it is possible that the leak is due to corrosion, tearing, or a soldered joint failing. Drain it as much as possible before disturbing the joint.

 

[sooey]

And don't make the mistake of thinking that turning off the stopcock and running a tap till the loft tank is empty means that the cylinder is too. It isn't.

 

[HarvestMoon4]

And don't make the mistake of thinking that turning off the stopcock and running a tap till the loft tank is empty means that the cylinder is too. It isn't.

Ohhhh there is no loft tank.

 

[JohnD]

then there is probably a cold water tank perched on top of the cylinder.

 

[HarvestMoon4]

Oh.......... I shall have a better look when I'm over there tomorrow, thanks for your reply btw