Repairing cast iron downpipe?

[Lobster]

Investigating the cause of a damp patch on an internal wall, I discovered a crack in a cast-iron downpipe; looking at it more closely I found that the crack actually runs the entire circumference of the pipe, and it's possible to raise the upper section and see daylight between it andthe lower section.

Bollocks.

I know it would be a relatively trivial matter to replace the downpipe with a 'nice new' plastic item; however, I'm rather attached to my original 100- year-old cast-iron rainwater goods, and I'd really prefer to hang on to it and repair it instead.

What would be the panel's reccommended method?

Thanks

[Ian Jackson]

In message , Lobster writes

I'd be tempted to fashion a sleeve - possibly from a bit of plastic pipe of similar diameter or slightly larger diameter. Cut the plastic pipe in half - into two 'shells' - that can be offered up to each side of the cast iron pipe. To get a good fit, a hot air gun can be used to soften and slightly re-shape the plastic pipe.

The actual gap in between the two halves of the pipe could be bridged by self-amalgamating tape (although this might not be necessary)

Butter-up the inner sides of the two halves of the shells with car body filler (preferably the plastic type of Plastic Padding), and place on each side of the cast iron pipe to form the sleeve. Hold in place with wire or very large cable ties - or something much more businesslike - like say several large Jubilee clips ('in series', as required).

[Nightjar]

As all you really need to do is stop it from leaking, I would lift the upper part, clean the faces as best you can, apply gutter mastic and join the two parts again. If it makes you feel more secure, put a bit of flashband around the back half, covering the join.

[John Rumm]

If you want the "complete" repair, then clean off the paint, grind the edge down so that the join is vee groove, preheat both bits to a couple of hundred degrees, then braise in a joint. Once cooled off, grind flat and repaint.

for an easier repair, cut the pipe with an angle grinder and stick in a coupler. Cover that with a cast effect pipe shroud. e.g:

then

[Bill Wright]

Halfords and B & Q do very long ones. About 1m I think.

Bill

[Ian Jackson]

They would be perfect. I'd use four of them - one at the top and bottom of the sleeve, and one about an inch either side if the break.

But just a thought...... There's been a gas leak (on three occasions) in the cast iron mains pipe buried deep in the verge outside my house. The pipe was about 4" diameter, and they used a purpose-made sleeve to fix it. Presumably the gas repairers have a stock of standard sleeves of various diameters, so it might be useful to contact them to see if they can supply one. Of course, such sleeves may be a standard part elsewhere in the construction industry.

And a further thought.... Instead of car body filler, why not consider something rubbery - maybe a piece of smooth rubber matting about 3mm thick.

[Nightjar]

I buy mine, in the exact size needed*, from my local branch of these people:

They do a very quick delivery and are cheaper than buying the same clips from the local agricultural supplier. If you do go down this route, which I think will look awful, remember to specify stainless steel Jubilee clips.

• Sizes here:

[Brian Gaff]

if the pipe is painted though you would need to get rid of that. Most cast iron is not that smooth, so you would need some kind of non shrinking filler as mentioned.

A word of warning though. Are you absolutely sure there are no other cracks in the pipe? It tends to happen to cast iron if under any stress for a long time that cracks grow and propagate, depending on where the minute flaws are. It might be that in the end a new plastic pipe is less of a hassle. Brian

[Bod]

That sounds like a complete lash up. If he wants to preserve the authentic look of the pipe, he'd do better to Google for a replacement pipe for that particular cracked section, IMO.

[Nightjar]

Certainly a better option, but he did ask for a repair and IMO, this is the simplest way to meet the need to stop the leak. BTW it should be possible to get an identical looking replacement in cast aluminium, which is easier to handle and is less brittle.

[Bod]

On 14/11/2014 11:40, "Nightjar

[Nightjar]

[Tim+]

Seems a lot of trouble for an unattractive result. I would have thought a bit of flashing tape like this would be adequate.

Tim

[Bod]

On 14/11/2014 13:56, "Nightjar

[Lobster]

On 14 Nov 2014, John Rumm grunted:

Range/110mm-

Range/110mm-

Thanks all for the replies - some really useful info there. I think I may use a hybrid of several responses! I've stopped it leaking for now with h/d polythene sheeting and wire, so hopefully this job can now wait till nicer weather next year.

Am particularly interested in the plastic 'lookalike' cast-iron stuff above (or the Al range mentioned elsewhere) - I've never come across that before. I have an immediate application for it. Several years ago we had a block-paved drive done; there was a rather odd but quirky short length of original downpipe which traversed a wall at 45 degrees to a gully in the drive, but was admittedly in need of some maintenance. I came home to find that the paving guy had removed and destroyed it, and fitted a replacment modern placky component - a perfectly competent job, and as he proudly said, at no extra cost - he took great pride in his work and liked to leave a neat and tidy job and a happy customer. "Thanks very much" I said, while inside screaming "AARGH - NOOOO!"

[newshound]

I'd go for an *internal* sleeve; standard downpipe is probably too large, but cut a suitable width axial slit so that it springs inside. Fix with non-setting mastic, this can also be trowelled into the external crack. Obviously, you would need to take down at least part of the downpipe to do this.

[Celebration]

replying to Lobster, Celebration wrote: So Lobster, interested in how this story ended: what did you did and are you happy with the result? I'm in a similar position, two front drainpipes in need of TLC but the local tradesmen just want to rip them all out and replace with plastic (although I know cast-iron effect is an option, it feels like an act of cultural vandalism on an 1880s house!) I need to act swiftly as scaffolding is due to come down at the end of the week!

[harry]

2014???!!!

[Brian Gaff]

Yes it was a while ago. I'm sure back in the old days we used to repair such pipes at least temporarily with car body repair kits then paint them the same colour as the pipe! Brian

[GB]

It's always the back of the pipe that rusts, where you can't get to it. Is that sod's law at work, or is it because it's usually not painted there/stays wet longer/some other reason?