Let’s begin with a caution: it is always best to treat any chemical or solvent as potentially hazardous and handle it with care and always wear protective eye and face protection as well as protection against inhaling hazardous fumes.

Wherever possible, handle chemicals in a well ventilated area and ensure that children and pets are kept well away and that the chemicals are stored in secure containers, secured out of reach of children and anyone else, and in the correct conditions.

Before we begin with the mundane tasks of clearing drains and bleaching wood, make sure you read the information at the end of this article by clicking on the link to the United States Centres for Disease Control (CDC) document on dealing with health issues relating to exposure to caustic soda. It’s comprehensive and well worth knowing.

Sodium hydroxide, commonly referred to as caustic soda, and also known as lye, soda lye, and sodium hydrate, is a white solid ionic inorganic compound with the formula NaOH, and it is soluble in water, ethanol, and methanol. While not flammable itself, being a non-combustible solid, it absorbs moisture from the air and if placed in contact with water while it its solid state, it may generate sufficient heat to ignite combustible materials.

It is a highly versatile substance used to make a variety of everyday products, but we usually know it best for it use in commercial drain and oven cleaners, and soap and detergents.

Drain cleaners that contain sodium hydroxide convert fats and grease that can clog pipes into soap, which dissolves in water.

The chemical also has a wide variety of other uses, which need not concern us here, but for interest sake include medicines, pharmaceutical products, from common pain relievers like aspirin, to anticoagulants that can help to prevent blood clots, to cholesterol-reducing medications.

It is even used in foods, water treatment and the manufacture of paper and also to refine raw materials for wood products such as cabinets and furniture and in wood bleaching and cleaning.

Right, having covered that, let’s take a look at using caustic soda to clear the drains in your home.

Most homeowners simply pop the plug into the bath, basin or sink’s plughole, fill up with hot water, add some flakes of caustic soda, stir a bit to dissolve it, and then pull the plug out. And that works pretty well.

But perhaps this method will work a little better…

  1. First of all, as with any product you buy from any hardware store – as if you should go anywhere else but your local Mica… read the instructions on the container, before opening it – and then follow those instructions to the letter. As you can see from this container of caustic soda, there is a comprehensive list of guidelines for handling the chemical properly and safely. They are there for your benefit. Read them follow them.
  2. The basic protections you need to wear: an apron, stout gloves rated to handle dangerous chemicals, eye protection (goggles or wrap-around safety spectacles); a respirator face mask. This version provides a very tight fit on the face and includes a filter to prevent the inhalation of harmful chemicals. At a push you can wear a cloth or paper face mask – we should ALL be wearing them now when out, so you will have one – but a purpose-designed unit as shown here is your best option. In passing, it also is best to wear old clothes that you won’t mind having the odd splash of bleach land on.
  3. This is why they pay plumbers the big bucks… a drain outlet gully is not a pretty sight. First of all, when you have multiple outlets as here, have your better half run water into each basin/bath/shower in turn so that you can identify which outlet is which.
  4. Now ball up a plastic shopping bag and shove it into the outlet pipe as firmly as possible, leaving the handles free as shown. It need not be leak proof – in fact it’s better if it does allow a slow ‘leakage’ as the aim is to slow the outflow while allowing the caustic soda solution to remain in the drainpipe for longer.
  5. Add the hot water to the basin from the tap and/or a kettle, and then add a tablespoon or so of caustic soda flakes. Hint: I put the flakes into an old tin and then sealed the main container; that way, if there is any splash, only the chemical in the can will be affected (in any event, try to avoid any splashing when you add the flakes to the water). Leave the caustic soda to dissolve completely.
  6. Back outside, leave the bag in place for a few minutes – while watching that it allows a little leakage, but otherwise stays in place. Then using the handles, pull the bag out and be amazed – if not a little put off – by what comes out of the pipe. If you wish you can repeat the process a second time to be absolutely sure that the drain is now clear.
  7. The same process is repeated with the kitchen sink. In fact, it’s a good idea to prioritise cleaning the sink drain on a regular basis as food waste, fats and heaven-knows-what goes down the drain and can slow or even block the pipe. Some hot water was added then some flakes were poured into the plug hole – to ensure a strong mix in the pipe itself.
  8. As per clearing the basin drain, the same plastic shopping bag did its duty again.
  9. With the sink/s full or a hot caustic soda solution, the bag was removed – and the drain was cleared and cleaned.
  10. As an additional step, in both cases – basin and sink – I topped up both having added some dishwashing liquid to get rid of any caustic soda solution residue. Given the fact that caustic soda is very corrosive and potentially hazardous, do this with every basin, bath and sink to ensure all vestiges of the caustic soda have been thoroughly washed off ALL surfaces and down the drain.
  11. You can use the same process for the shower but also get the effect of pulling the plug, as with the basin, bath and sink by filling a second plastic shopping bag with soil and dropping it from about 450mm onto the shower outlet. That means the bag will tend to seal the gaps between the tiles by conforming to the surface. Meanwhile you will already have blocked the outlet pipe in the gully outside, with the first bag.
  12. With the bag in place, run hot water into the shower and add the caustic soda flakes. When you are ready, remove the bag and the bag plug in the outside gully and your shower drain will also be cleaned thanks to the very strong slow of water from the shower floor.
  13. Now for bleaching or lightening wood… it always pays to experiment on the same sort of wood as your workpiece. In this case, I placed one example each of meranti, cork and SA pine in a solution of caustic soda and left them in it for about 20 minutes.
  14. In this particular case, there was a barely discernable change in the meranti, the cork became darker, and the SA pine too, showed minimal change. The key, as mentioned just above, is experiment before committing to a final course of action.
  15. In this video you will see how you can bleach wood with sodium hydroxide and hydrogen peroxide (so it’s a two-part wood bleach)… In passing, the person doing the bleaching is wearing open sandals. That is NOT a good idea as bleach could splash on to the skin, and if the sandals are still in good condition, they might well not be by the end of the demonstration.

Health and first aid advice related to exposure to caustic soda

Due to its strong corrosive qualities, exposure to sodium hydroxide in its solid or solution form can cause skin and eye irritation, according to the US Centres for Disease Control and Prevention Agency for Toxic Substances and Disease Registry.

Sodium hydroxide does not produce systemic toxicity, but is very CORROSIVE and can cause severe burns in all tissues that it comes in contact with. Sodium hydroxide poses a particular threat to the eyes, since it can hydrolyse protein (hydrolyse means to break down a compound by chemical reaction with water), leading to severe eye damage.

According to the same CDC document, you need to call your doctor or your local emergency department/paramedics if you develop any unusual signs or symptoms within the next 24 hours.

In particular, look out for the following:

  • Drooling or difficulty swallowing
  • Stomach pain or vomiting
  • Coughing, wheezing, or hoarseness
  • Difficulty breathing, shortness of breath, or chest pain
  • Increased pain or a discharge from exposed eyes
  • Increased redness or pain or a pus-like discharge in the area of a skin burn

To read the full document, click here

The bottom line with caustic soda or indeed any other symptoms or affects of exposure to chemicals is always be ready to err on the side of caution, without being paranoid, of course. If nothing else phone your doctor or the local hospital, describe exactly when has happened and the results, and then follow the advice you are given.

Also bear in mind that no article, even the one to which we have linked above, substitutes for professional medical advice and treatment. When in ANY doubt, seek expert assistance and advice. 


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