C/H pipe crusty and leaking

YorkshireMidge · 7 May 2019

Just noticed a couple of small brown stains on the kitchen ceiling today, from our main bathroom above. I was expecting a leak somewhere, but not the one I actually found - which is a very crusty looking central heating pipe under the bathroom floor.

I can't actually get to this from above as the bathroom floor is tiled on top of a base board, and it would mean re-laying it - so I'm going to have to cut a trap in the kitchen ceiling over the next day or so, and work from below. No work has been done in recent years - but equally, it looks like it could have been dripping very slowly for some time and suddenly gotten worse.

I can't see it being a patch of corrosion as the system has had corrosion inhibitor in it. I suppose a screw into the top of the pipe when the base board was put down is possible but this looks a bit too crusty for that sort of problem. Anyone seen anything similar?

Thanks!

JohnD · 7 May 2019

is that a split in the bottom of the pipe?

YorkshireMidge · 8 May 2019

JohnD said:
is that a split in the bottom of the pipe?

The same thought crossed my mind John - but the photo was taken by shoving my smart phone down a plumbing gap in the boards. I can't even see this, let alone get a hand to it. But there are definitely two c/h pipes running in parallel (I have confirmed this by pulling up a board in the adjoining bedroom) so it could just be a trick of the light and we're seeing a tiny bit of the second pipe behind it. I drilled a pilot hole in the kitchen ceiling last night and after the pool of water had drained, it's dripping at a rate of a couple of drops per minute. If the pipe was split, I was thinking it would be much worse + I can't see why the gunge would be right around the pipe.

Looking at my photo again, there is a noticeable peak in the crystals on the top of the pipe so I'm thinking that might actually be where the water is coming out - and is perhaps hiding a screw.

dilalio · 8 May 2019

From what the photo shows, You're gonna struggle to repair that from below!

lostinthelight · 8 May 2019

Are those fixing clips for pipes joining at 90 degrees?

YorkshireMidge · 8 May 2019

dilalio said:
From what the photo shows, You're gonna struggle to repair that from below!

Yup - but have a multitool so I'm confident I can chop the old pipe out from below if I drill a pilot hole first to drain out any water that might be sat in there once I drain-down, and just have to hope there is enough movement in the pipe to get my soldering mat between it and floor board above. If you go easy with a multitool, you can chop a copper pipe without distorting it so it just needs a light de-burr to get a fitting on.

lostinthelight said:
Are those fixing clips for pipes joining at 90 degrees?

No. The solder joint you can see is a 90 degree bend which takes the affected pipe through the middle clip of the three. The second C/H pipe hidden behind goes through the left hand clip. The right hand clip is for a separate cold water pipe.

dilalio · 8 May 2019

YorkshireMidge said:
Yup - but have a multitool so I'm confident I can chop the old pipe out from below if I drill a pilot hole first to drain out any water that might be sat in there once I drain-down, and just have to hope there is enough movement in the pipe to get my soldering mat between it and floor board above. If you go easy with a multitool, you can chop a copper pipe without distorting it so it just needs a light de-burr to get a fitting on.

Can't beat a multitool... I have a 240v bosch and an 18v makita with tool-free blade swap... they've saved many a day

Try and wedge a couple of chisels above the pipe to pry it away from the undersides of the floor boards, it'll help you with the cutting and with wicking the flame around the pipe when soldering. I have a few small sheets of tin flashing pieces (scrounged from various sites where roofing work is being done) and these are ideal for heat protection in tight spaces and when used with a couple of chisels - as wedges - you can create a convex shape that keeps the back of the joint to be soldered out of contact with anything. (local builders merchants should have them) or you may have something similar around the house/garden/shed?

foxhole · 8 May 2019

Solder joint appears to have failed , joints not cleaned properly can fail after a few years as flux paste eats into pipe if not wiped away.

YorkshireMidge · 8 May 2019

dilalio said:
Can't beat a multitool... I have a 240v bosch and an 18v makita with tool-free blade swap... they've saved many a day

Try and wedge a couple of chisels above the pipe to pry it away from the undersides of the floor boards, it'll help you with the cutting and with wicking the flame around the pipe when soldering. I have a few small sheets of tin flashing pieces (scrounged from various sites where roofing work is being done) and these are ideal for heat protection in tight spaces and when used with a couple of chisels - as wedges - you can create a convex shape that keeps the back of the joint to be soldered out of contact with anything. (local builders merchants should have them) or you may have something similar around the house/garden/shed?

Thanks for the ideas. Mine is a Bosch mains one too and it's a fantastic bit of kit (hence my comment about drilling a pilot hole to make sure all the water is out before using it below a pipe!). I was thinking if I get really stuck, I can always chisel out a slight recess in the underside of the floor boards too.

foxhole said:
Solder joint appears to have failed , joints not cleaned properly can fail after a few years as flux paste eats into pipe if not wiped away.

I've just cut the hole in the ceiling over the last half hour, and it looks like you could be right. Whatever it is has got to both joints which tends to rule out screws. I know what the screw that is visible is for, and I can't see any others in that area. I didn't realise flux was that corrosive - is it a feature of older fluxes (this will be the original pipework from when the house was built around 30 years ago) or does it apply to modern stuff too? The flux I use is Fernox Powerflow.

YorkshireMidge · 8 May 2019

Thought I'd share the post-mortem photo now I've managed to cut the pipes out. The fitting of the inner pipe has rubbed through the wall of the outer one - and you can see the hairline crack in the one on the left. What seems to have happened is there has ended up a solder bridge between the two and you can see the bulge in the previous photo. So my assumption would be the bridge was free to rub against the pipe on the left.

JohnD · 8 May 2019

Is there a bulge like you get when a joint is formed by hammering a tapered drift into one copper pipe to form a socket into which another pipe could be inserted? That may also have started the crack.

It saves several pence but in the examples I've seen the failure rate is higher than usual.

ianmcd · 8 May 2019

+1 for flux being left after soldering

YorkshireMidge · 8 May 2019

JohnD said:
Is there a bulge like you get when a joint is formed by hammering a tapered drift into one copper pipe to form a socket into which another pipe could be inserted? That may also have started the crack.

It saves several pence but in the examples I've seen the failure rate is higher than usual.

No, there's nothing like that John. I think it's just careless soldering. As I mentioned above, you can see in the photo taken from beneath where the solder lump on one pipe was in contact with the other - and that is where the hole has worn through. You can actually feel the depression in the tube surface.

ianmcd said:
+1 for flux being left after soldering

There's definitely flux been left. Difficult to say whether it contributed, but I don't think it was the cause.

dilalio · 8 May 2019

As per my tip about using a tin (metal heat shield) keep the joint contact-free of any other surface to avoid bridging... And be ultra fussy about cleaning away any residue flux after

ianmcd · 9 May 2019

YorkshireMidge said:
There's definitely flux been left. Difficult to say whether it contributed,

you would be surprised just how aggressive flux can be,dont see as much now with PE being used for most jobs but used to see it all the time , its my pet hate to see verdigris all over joints when all it takes is a second to wipe clean once the joint has cooled

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C/H pipe crusty and leaking

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