Sealing a leaking strap boss onto 3 inch LCC (Cast Iron)

[Gusterado]

Hi
I've been asked to re seal a plastic strap boss which someone has bodged onto an cast iron waste stack. The strap boss is just above the old cast iron collar. The hole which it discharges through into the stack has been drilled slightly too small to work with the ridge on a 3 inch plastic strap boss...This was not my mistake initially, but through bad luck it has fallen to me to resolve it as quickly, cheaply & professionally as possible Is there a proprietary fitting which can re make the joint easily ? Any suggestions & help would be appreciated

 

[Ric2013]

This is something I have often thought about myself as it seems ridiculous if you can't put a saddle boss onto cast for the sake of lack of a suitable fitting.

As far as the hole is concerned, I would think you would be able to file it out or use an abrasive stone held in a drill/Dremel/etc. Or perhaps a holesaw? I have used a holesaw on a cast iron hopper before now.

At college we were taught that cast iron is incredibly hard and brittle and almost impossible to work with. My teacher then admitted she hadn't ever actually worked with it. My own experience with cast rainwater goods is that cast can be cut with a grinder fitted with a metal cutting disc and can be drilled with standard metal bits. When drilling, I never lubricate (the carbon in the iron is sufficient) and I use my combi drill with a low ratchet setting to reduce the risk of cracking the gutter if the bit snags at the end of the hole. Hopefully you will be able to translate this advice into something relevant to your hole issue.

 

[snowhead]

This is something I have often thought about myself as it seems ridiculous if you can't put a saddle boss onto cast for the sake of lack of a suitable fitting.

What like this one (not to be confused with BOSS-Cast which is 22mm hole and only suitable for condensate);

Black Mechanical Soil Pipe Boss Connector

 

[rpm]

Use a multi tool and cut away the old boss completely. Then file the hole out to required size and remove rest of the boss with a flat file and start again.

 

[gmartine]

Agree with above if I've read your problem correctly, open up hole to fit as well as trim down boss.

 

[Andyh]

If creating an effective seal is the issue try ct1

 

[Last Plumber]

I hate botch work but when you're faced with dealing with the remnants of some plant pot's work, what can you do?
The best solution is always to put the whole thing right but that will be seen as extreme I know.

Cast iron is brittle but soft and easy to work with when Cutting, grinding, drilling, tapping, filing etc etc.
I would do as @Ric2013 said if the hole is too small. Open it up a bit, clean the surfaces off and seal the boss in. you could use CT as someone else mentioned if the strap holds it in place tight enough.

 

[Ric2013]

What like this one (not to be confused with BOSS-Cast which is 22mm hole and only suitable for condensate);

Black Mechanical Soil Pipe Boss Connector

I'd be inclined to try to see if it fits. While I would prefer to fit steel or iron to iron, if this works well, then it isn't a bodge. Seems downright wasteful to scrap a perfectly decent iron stack just because you want to add a new connexion to it.

 

[gmartine]

Picture would be handy?

 

[chris watkins]

Black Mechanical Soil Pipe Boss Connector
The newer version of the Fixacon
57mm hole required