Hello everyone. I'm bringing on a job before my plumber comes. It's a downstairs toilet and basin in the old pantry. I'm leaving all copper exposed including copper wastepipe and using copper elbows. There are two easy solutions to where my waste pipe will exit. I can either use a boss into the soil pipe or use a mcalpine elbow and spray it copper onto the grey waste exit you can see on the pic. My question is: I'd really like to find a way of sealing the copper elbow onto the grey waste protruding from the wall. It fits snuggly on, but obviously no seal at the moment. Has anyone got any knowledge of washer inserts into copper elbows, or had any success using just silicone, or know of any other solution??? Cheers