leaking connection on the feed pipe to an indirect cylinder

Hi, I have a leak on my indirect hot water cylinder. If you take a look at the picture on this link -
http://tinypic.com/view/?pic=2zq776r
it is leaking not from where someone on another forum marked his leak but from between the cylinder face and the washer beneath the
nut. This is on the top feed of the coil and I don't know whether it is boiler water or tank water that is leaking.
Putting the heating on demand doesn't seem to make it drip any faster.
I'm not sure if tightening the nut nearest the cylinder will have any effect.
I would guess that it was part of the original factory assembly and tightening it may try to turn the coil or even break a soldered seam!
To make matters worse I have a complicated set of fittings, including a cast iron sleeve, between the nut and the elbow on the feed pipe which means that each thread back would be loosened in turn.
The tank (not foam lagged) and pipework have been fitted for probably 40+ years so not sure what size pipework is.
Comments and suggestions would be greatfully accepted, thank you anyone.[/img]

it looks foamed lagged to me & it ain't 40 yrs old

CBF said:

it looks foamed lagged to me & it ain't 40 yrs old

Click to expand...

Was going to say same myself!

Not alot you can do about that without draining then stripping down the joint and remaking - I would think, I'm afraid!

That`s not the OP`s tank - he just used it as a reference

DAVYBOY88 said:

The tank **(not foam lagged)** and pipework have been fitted for probably 40+ years so not sure what size pipework is.
Comments and suggestions would be greatfully accepted, thank you anyone.[/img]

Click to expand...

Sounds like you have 2 choices - get a plumber to attempt to manipulate the connection to fix the leak - or get a new cylinder . Option 2 . you`ll need the correct cylinder for your existing setup - or maybe even a re plumb with better controls if you`ve still got gravity primaries . Any good plumbers in Hants ?. PS when those cylinders were new we always used to check the tightness of the backnuts It will have to be done by draining down as the other Sussex Plumber said - so contain the leak if at all possible and wait for warmer weather

Nige F said:

DAVYBOY88 said:

The tank **(not foam lagged)** and pipework have been fitted for probably 40+ years so not sure what size pipework is.
Comments and suggestions would be greatfully accepted, thank you anyone.[/img]

Click to expand...

Sounds like you have 2 choices - get a plumber to attempt to manipulate the connection to fix the leak - or get a new cylinder . Option 2 . you`ll need the correct cylinder for your existing setup - or maybe even a re plumb with better controls if you`ve still got gravity primaries . Any good plumbers in Hants ?. PS when those cylinders were new we always used to check the tightness of the backnuts It will have to be done by draining down as the other Sussex Plumber said - so contain the leak if at all possible and wait for warmer weather

Click to expand...

Thanks CBF, Beesey and Nige F, I'm not sure what is on the other side of the backnut in the cylinder.
If the backnut on the cylinder is not tight enough against the cylinder, what water do you think is leaking?
If it's the domestic HW from in the cylinder I could get away with just draining down the cylinder until the water level is below the joint to remake it.
If it's the central heating water though, I'll have to drain the CH system.
Many thanks again.

It`ll be the domestic hot water in the cylinder that`s weeping through . If it goes well you`ll get away with just the hot drained -

Thanks Nige F, I thought it would be the domestic water.
A pal and I tried to turn the nut without success - even hammering the spanner end wouldn't budge it - but have a plan.
The leak is minor, you can see it beading at the bottom of the washer then running down the cylinder. So I plan to drain down to below the primary feed, dry and clean the area and apply Fernox LSX then allow to dry for 24 hours before refilling.
I've heard on the forums that it can be unsuccessful but hey - what have I got to lose - if it still leaks then oh crap, I'll have to drain down everything and dismantle the joints somehow!
Many thanks again for your help.

DIY fix.
I have recently had this problem on an old cylinder, pre fome, and built in in such a way as to make replacement impossible without demolishing part of the bathroom. It was clear that trying to dismantle the union would almost certainly destroy the coil. My labor intensive fix:
Drain down
Clean up to shiny metal.
Grind down one side of a junior hack saw blade so that i can cut away the washer between tank and cylinder without cutting in to the tank.
Cut back washer which is less than 1mm thick about 4mm.
File and clean nut and tank surface to shine.
Use edge of sand paper to clean under cut.
A new wind in gasket with pre load is now needed.
Materials:
Blue Hylomar, a cylinder head gasket sealant.
Nylon thread, ~ 0.1 to 0.25mm Not polyester, because Nylon has stretch.
epoxy putty.
Cellulose thinners acetone (nail varnish remover) or cleaner specified for cement.
Fill undercut gap with cement.
wind thread into gap under tension forming a preloaded gasket in the undercut.
You now have a good water proof gasket, but its not mechanically stable enough to stand the constant movement of heating and cooling pipework.
Clean away every trace of the cement.
Insure the nut and an area around the union on the tank wall 20 mm wide is clean to bright metal.
Form a layer of epoxy cement over the nut, around the new gasket and about 15mm onto the tank wall tapering it away on all surfaces.
Leave 24 hours, and refill.
I have some pictures available. so far so good and a small fortune saved, at least until the tank fails big time.

Hi Rodbic and thanks for your reply. Seems ages ago that I had the problem and I managed to find a way to fix it.
Don’t ever waste your time and much money using Fernox Leak Sealer – the gravity water pressure balloons it over a week until it bursts while going green with the heat undenneath!
First I drained the cylinder hot water so it was below the leak.
Then I cleaned up the tank around the pipe so it was nice and shiny for about an inch all around. I also cleaned up all around the nut and washer as best possible.
My idea was to use 2 part epoxy and spread it all around the join so sealing up the leak. Ideally it needs to be high temp epoxy but I was getting desperate and took a chance on what I had.
Now, the trouble was going to be although the epoxy was quick setting, it's extremely runny until it starts to set. I therefore had to devise a means of keeping it around the joint and not drip off.
Next I hunted for a large rubber washer from my old plumbing box. The one I used was about 3" diameter, an eighth" thick and with a hole in the middle that would go around the nut. I know what you're thinking - how does it go around the nut? Well, the hole in the middle was actually a bit big so I cut across the washer and also kept removing small amounts in cuts radiating from the middle so that the 2 cut ends of the washer, when closed around the nut, would not only meet but would form a taper from the base of the nut, passing over the washer and then meeting the tank surface.
Now the really tricky bit – preparation is key. First get some mechanic/surgeon style rubber gloves and put at least 3 pairs on – that way when one becomes too stick you can pull it off down to the next. Try to mix up enough epoxy to do the whole job so you’ll probably waste some.
Having mixed it I used a narrow spatula to spread loads around the nut, washer and cylinder but not so much that it would drip. Then I spread copious amounts on one side of my rubber washer, applied it around the nut and closed the ends together while pushing it against the tank surface. It’s a really messy job especially in an awkward position like mine was, trying to hold it while balancing the rest of the epoxy on a board. While it was setting I put as much as I could on top of the rubber washer and kept applying, spreading and pushing to keep the ends meeting with my fingers. I found after 5 minutes or so the gloves didn’t stick so much.
I guess you could do the job in stages i.e. just sticking the rubber washer first then applying more epoxy when that has set.
I think I started the central heating straight away so that the heat in the pipe would set it off quicker then I refilled the tank after a few hours.
Bingo! – no more leaking and that was at least a year ago.
Hope this is useful to someone else with a similar problem.