Sealing a cast iron downpipe.

Hello,

I have a leaking cast iron downpipe at the point of a join where the hopper meets the downpipe. I'm not sure if it has been repaired before as it has a grey putty around the seal which is a totally different colour to the black pained pipe.

I can't really afford to replace so I plan to take it apart, wire brush the rust off both parts and clean them up, then replace and seal or fill with some caulking and then put new waterproof putty on to seal it. I then plan to paint it black if that's possible.

Is this the correct way to do it and what is the best putty to use please?

 

Hello and thank you all for your replies. I will have a good read of the recommendations.

In relation to Mr. Handandy's comment I admit I am confused too! There is a cast iron pipe coming into the hopper (halfway up the wall of a two storey house) at an angle and one from directly above (short plastic pipe), there is then a cast iron pipe that goes to the ground.

The issue is that there appears to be signs of damp/white marks on the wall but only behind the cast iron pipe that runs from the hopper to the ground and only around the back of the pipe between the ground and about three foot up. I can't see any other place that it can be coming from, when I checked the seal it was all cracked and when I moved it around a little water droplets came out of the seal. I have checked inside the hopper and there are no signs of leaves or blockages, although its possible it was blocked and backed up but has now cleared.