INGREDIENTS:
1) Hammer and chisel
2) #Sewerin #Utilitrac and radio transmitting #Sonde
3) #Drain #Cam
4) #Picote Mini Miller
5) #Epoxy delivery pump
6) Hand tools
7) Delivery hose, cutting chains, coating brushes and general coating consumable
8) A builder to patch things up

METHOD:

Use some logic, plumbing experience, the drain camera with flexible reel, Utilitrac and the Sonde to find the hidden drain stack in the wall.

Chop the wall to expose the drain stack once located, flushing water from the bathroom above (using leak detection dye to identify each point.

Remove some plaster to rule out the presence of a hidden waste pipe.

Once the leak is simulated, follow it until you reach the concrete slab above, to find the junction and can’t chop any further. The dye will indicate which points are connected to the junction by colour.

Cut a section out of the stack and inspect the pipe upstream to reveal a large crack above the Junction and all connections that couldn’t be accessed from above, which have all contributed to the leak, through this crack.

Send the Flexshaft from the Mini Miller, spinning at medium speed, with a carbide chain at the end to make the pipe rough, while blowing warm air through the waste pipes above. This will dry the pipe and prepare the pipe walls for an epoxy coating application. The epoxy will stick better to a rough pipe wall. (A sanding hub can’t be used here, because it flares and won’t fall backwards into the junction branch that you need to access).

Pump epoxy through the delivery hose and into the pipe. Brush it onto all the inner pipe walls and into any cracks and gaps along the way, using the coating brushes at the end of the Flexshaft, spinning slowly and pulling back. Watch everything through the drain camera to judge your pace and speed of the pump.

Once the coating is complete, allow for 12 hours to dry.

Return the next day to get a camera into the pipe and inspect your dried epoxy work, before replacing the pipe section you removed from the stack pipe.

Flush test everything many times.

Ask the builder nicely to rebuild the wall.

Clean up and say goodbye.