Clearing Gullies
Gullies, particularly the old open sort are very common sources of blockages. If the blockage is in the trap, you can usually clear it from the gully itself. But if all else fails, rod in a plunging motion up the inlet in the inspection chamber that leads to the gully.

Small gullies can be baled out by hand. Life the grid then wearing rubber gloves, scoop out the debris into a bucket. Check that the outlet is clear with your finger: if it isn’t try poking some coat hanger wire up it.

Gullies receiving sink waste get clogged with grease. This can usually be shifted with boiling water or scraped out by hand. If this does not work, try pouring down a solution of caustic soda. But take care and follow the instructions to the letter – caustic soda is dangerous.

Deep gullies and blockages on the other side of the trap can be shifted by plunging – you can get an attachment like a sink plunger that screws onto the end of a ordinary drain rod. A household mop makes an effective standby as do old rags wrapped in a plastic bag and tied to a broom handle, but only if there is enough bulk to fill the gully neck completely.

You could try threading a garden hose around the bend in the gully trap to flush the blockage with water. In this case stop up the gully itself with polyethylene bags rammed tightly in place – the extra pressure this creates will help the was do its work.

Note that in some drainpipes rodding eyes are provided at places where blockages may occur.

Blockages in Stacks
These are rare in single stack systems and simple two pipe arrangements, but common in older, complicated drainage layout. Fortunately there are often clearing eyes at junctions and direction changes.

Soak eye covers in penetrating oil before attempting to remove them.
You can then either insert a rod with a head to match the stack diameter, or else feed in a screw clearing wire. Use the same procedure as for an inspection chamber.
Clear the hopper from above with a worm screw rod.

Tree Roots
These can work their way throught a joint in a drain pipe, in which case no amount of plunging will shift them. You may be able to clear them partially with a powered screw augur similar to the type used by professional drain clearers – they are available at some hire stores. But a more satisfactory solution is to excavate the drain at the site of the problem.

Find out how this is by making a note of how many rods in takes to reach the obstruction. Then lay out the same rods at ground level in the same direction and see where they end.

Dig down to the pipe, hack away and pull out the offending roots, then make good the damage to the joint with a strong mortar mix of one part cement and two of sharp sand.

Summary
So there you go, four articles on how to clear blocked drains. I hope my writing has some how managed to help you with any drain related problems.