Engineering:Drain rods

Drain rods are plumbing equipment used to attempt to unblock drains and sewers. The set normally consists of several stiff, but flexible, rods, each approximately one meter long, which may be screwed together end-to-end. The material is often polypropylene heavy gauge tubing. Jointing of the plastic to metal is done in hydraulic presses and these joints are the achilles heel of this rod type. Often, when subjected to force, the joint breaks. Better quality ends have securing pins through the differing materials. More expensive rods are high tensile steel. End connections are often brass or steel, the better steel type having cadmium plating for corrosion resistance. Two types of threaded end can be purchased. Cheaper ones simply screw together, male to female but have the disadvantage of needing one-way rotation in use to prevent unscrewing. Better quality rods have their ends formed into a square peg, mating in a matching square hole in the adjacent rod. A captive threaded nut then screw locks both lengths together making a firm joint. A spanner tightens the joint firmly.

Usage

In use, this type of secure fixing enables rod rotation in both directions which is often necessary to clear blockages. Tree roots in particular often need 'winding up' before extraction and disposal. In addition the drain rod set usually has one or two unblocking tools. One may be a pivoting flat metal plate of almost half the drain diameter. It is hinged across the widest point. This tool can be rotated to ride over poor mortar joints or dragged over the joint to scrape any protuberance. An auger can be screwed onto one end, it may be a single helical coarse thread or even double helix. The latter being ideal to capture thin young tree roots. Various rubber 'washers' and bristle cleaning assemblies can be purchased too.

The screwed together rods and tool are inserted into a drain or sewer from an access point usually a manhole chamber, sometimes a rodding point or a clean out, and used to attempt to dislodge a blockage.

Rodding is the act of using a drain rod. It is usual to use a twisting motion to facilitate progress of the rods and flushing with water eases progress. It is important, no matter which way the rods are being moved (towards or away from the blockage) to ensure the twisting is in the direction to tighten up the screw connections as mentioned above. Any unscrewing of the rods whilst in the drain or sewer will lead to their loss and further blockage.

See also

• Plumber's snake