Unblock a Drain

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Revision as of 09:32, 11 February 2008 by (talk) (tabomonalv)
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darbol There are many ways to unblock drains. Always act before the blockage is total, as a total block makes getting chemicals to the blockage difficult to impractical.

Boiling water

Not the most effective, but will sometimes unblock fat blockages. May be tried if nothing else is to hand. Fat dissolving chamicals should then be used to clear the drain properly.


Sulphuric acid

Eats organic material, eg turds, paper.

  • Dont't mix acid with alkali.
  • Keep strong acids off chromework.

Hydrochloric acid

Eats organic material. More aggressive than sulphuric acid. A high risk chemical.

30% hydrochloric acid is sold as brick acid. Some patio cleaners contain HCl.

  • Never mix a strong acid with an alkali.
  • Keep strong acids off chromework.

Caustic soda

Caustic eats fats, which are the most common blocker of kitchen sinks. Boiling caustic is much faster than cold caustic.

Caustic is a high risk chemical. It burns skin and can cause serious eye damage. If you get any at all in your eye, it is important to seek treatment urgently. Delay in treatment (it doesnt hurt) generally results in serious irreversible damage.

Preparing boiling caustic solution sprays strong alkali droplets, and thorough eye protection is essential.

  • Caustic soda is a strong alkali.
  • Never mix a strong alkali with an acid.


These eat biological matter, but may take a very long time to do so.



Very effective mechanical unblocker. One of the more bulky and expensive pieces of equipment.

Metal tape

A reel of flexible metal strip or tape makes a low cost & physically small rodding device. Also sold in rotating containers for greater effectiveness.


2mm steel wire is enough to remove many types of blockage. Cost is minimal, and it is already to hand in many cases. 1mm wire is no use for this.

An advantage of steel wire is it can be fed in through a 5mm hole.

Wire does not generally clear a drain fully, but makes a passageway for water. the blockage should be fully cleared afterwards with a suitable chemical.


Block all other airholes, eg overflow. Push plunger down gently but firmly, and pull up with force. Good for sinks where the blockage is an accumulation of small pieces, eg food.


Insert hose down drain. Block all holes with towel. Turn hose on full blast. Prepare to get wet and make a mess. Good for all soft blockages.

Pressure Washer

Can unblock drains, but very messy, and unblocking sewage creates a health hazard. In the latter case full splash protection is desirable!

Suited to outdoor blockages.

Curtain Wire

Curtain wire may be used for clearing blockages close to access points. A metal tape tool is better, with much greater reach.

Access points

Rodding eyes

Drain covers

Open pipe ends



Re-assemblable joints

  • Compression
  • Some pushfit

Drilled hole

A 5mm hole allows a steel wire to pass inside the pipe. This is useful for solvent weld pipework with no means of access. A 5mm hole is drilled, and capped after use with either

  • a piece of plastic pipe and some pipe welding solvent, or
  • a piece of rubber, a bent washer and a cable tie

See Also

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