Best way to fix joint in a leaking downpipe?

[NomoneyNohoney]

I've probably got a leaking downpipe to fix, which is leaking at a joint. Previously I've used weatherproofing tape, and wondered if there's any better products to use?

If no better method is suggested, am I right in starting wrapping the tape a few inches below the joint, and then winding round and upwards, so that the upper levels of tape overlap the lower levels? Or is it better to start higher and work downwards?

[jfgw]

What is the downpipe made of? Why does it leak? Is it cast iron? Is it cracked?

Replacement would be best and should last the longest but, if you don't want to replace it, you could use Denso tape (or a similar petrolatum tape) to patch the leak. It probably doesn't matter where you start but, if you are trying to keep the water inside from coming out, I suggest starting at the top and working down.


Julian F. G. W.

[NomoneyNohoney]

Looks like its an iron pipe, probably 100 years old. Why does it leak? Dunno, but its at a joint.
I think the weatherproofing tape I've got is probably like what you describe as Denso tape. Mine is a 3" wide type of canvas, impregnated with green clayey, sticky stuff. You wrap the tape round and then smooth the outside with your (gloved) hand. Is that like your Denso tape?

[bionichamster]

I've repaired a few cast iron downpipes and fitted some new sections into old ones. On one tenement the gaps between each section (i.e. where the pipe from above sits into the collar of the pipe below) were filled with what appeared to be a lime mortar and some sort of cloth mesh for reinforcement. I'm pretty sure that the 'lime mortar' was actually some sort of aged fossilised putty as I believe using linseed putty (sometimes with other additives) was a common method of packing the joints

To emulate this I used a bit of denso tape packed in the collar and topped it with window putty for the replacement, it was still holding many years later when I moved. I used the denso mainly to stop the putty falling inside the pipe because it was a largish gap. On another much tighter fitting joint I just used a small amount of Milliput (epoxy putty). I also repaired a crack in one pipe using black miliput, I gave the crack a good clean and rubdown and squished the miliput in and smoothed it out, then sanded and painted once set, (all done hanging out of a second floor tenement window to reach it), the repair stopped the leak and was still holding many years later.

BH

[foundone]

I'd have thought the leak is due to a blockage if it is a downpipe,they aren't intended to hold standing water, if it's a feed into a downpipe it should have a slope of at least 15 degrees. You may find drainclear or a vigorous rodding will fix it.

[88V8]

I'd have thought the leak is due to a blockage if it is a downpipe, they aren't intended to hold standing water, if it's a feed into a downpipe it should have a slope of at least 15 degrees. You may find drainclear or a vigorous rodding will fix it.

The joints are not meant to be watertight.
As foundone says, you have a blockage. You're trying to fix the symptom, you need to find the cause.

New iron pipes here
http://www.longbottomfoundry.co.uk/

V8

[bungeejumper]

The trouble with 100 year old cast iron downpipes is that they didn't always remember to put in rodding points for clearing blockages. (Which I'd agree is probably the ultimate cause here.) And cast iron is an absolute bugger for drilling out the hole for a new one. I've managed a square hole with a small angle grinder, though. If you can't get a proper rod up the pipe, try using a length of mains electricity cable folded back on itself to extra rigidity. Or even a pressure washer jet from below. (Might take a while, but worth a try if the blockage isn't too far up.)

Try tapping the pipe to hear where the problem's located. And you can also get an idea of where your blockage might be by the simple expedient of climbing up a ladder and filling the downpipe with water from a hose. There should be all sorts of tinklings and gurglings that will give you clues.

We have square section cast iron pipes here at Bungee Towers, and when we bought the house 22 years ago (as a restoration project) the damage had already been done. A blocked downpipe had filled with water, and had then frozen, and the pipe had busted out and was flooding the wall.

That in turn meant that small triangular lumps of cast iron were down in the downpipe, but we just had to learn to live with those. It was either that or replace the whole caboodle, which would have been a major scaffolding job and more money that we felt like spending. Being mean/broke at the time, we decided to hope for the best, and to repair the cast iron pipe with metal gauze and chemical metal/plastic padding. (Scrupulous cleanliness and preparation is the key.) 22 years later our luck is still holding and the fix still looks perfect.

BJ

[quelquod]

Is it leaking significantly, running out, or just a dampish seeping.

If the former then as 88v8 says, you likely have standing water inside and it needs rodding. If it's just seepage I think it's likely a bit of corrosion and muck holding enough water to let it dribble through the joint and some waterproof mastic squidged into the joint should hold it.

Denso tape - wonderful stuff but yeughhh, the mess!