Caustic soda (Sodium Hydroxide) NaOH : To unblock my drain. I know nothing of chemistry just using logic, please help me.

[yosafa]

Hi Everyone, 

Firstly, I would like to apologise as I am not as knowledgeable in the science field hence me requiring the help of you all. I need to know about the chemical reaction and consequences relative to my query and questions below. 

Thank you to all in advace for your answers and advice.  

____________

The outdoor garden drain is blocked quite severely with years of fat, oils, grease build etc.. Most likely from the previous owner of the home, with the addition to my own. 

The problem started as I noticed my kitchen sink was not allowing water to drain and was coming back up. 

I change the old trap, u bend and waste pipe. The waste pipe comes out the external garden warn and into the outdoor drain gully grid. I replaced all waste pipes from the sink, all new, but the problem was still happening. 

I did not notice the water at the time was rising from the outdoor drain until today which then indicated a drain block coming out of the gully grid. I removed the grid and removed a lot of thick fat & grease by hand.

Problem/solution/Questions. 

Even though I have unblocked the drain a little bit, there is a lot of remnants of fat and grease left which has tucked into the grooves of the drain pipes. I have tried going at this with drain rod, and pressure washer jet washes pipe, though it just will not budge. 

I was thinking of using a chemical such as caustic soda to eat away the fats and eventually block the drain though I worry about using such chemical. My worries are

1. Will caustic soda actually do the job of unblocking the drains?

2. If I was to pour in the diluted caustic soda, will it eventually harden again elsewhere in my drainage system causing a major block or will it just wash away the cooler it gets from the moist? From reading and guidance, the Caustic soda should be added to cold water as it heats up which then can be poured into the drain according to ratio guidance on the label. Additionally, this chemical is known the harden

3. Because the chemical gets hot when reaction with water, will this in turn damage the underground PVCu Drainage pipe or again will it just cool and wash away. I know the PVCu has high heat resistance though, does the chemical pass the PVCu heat threshold which may then cause damage. 

If all else fails, then could you guys recommend me a possible home remedy or ideas to just unblock the grease and fat leaving it overnight etc... then wash away. 

Sorry guys for the many questions, though, I hope you can all help me regarding this. I just want to be sure before putting anything in my drains which may do potential harm.

Thank you to all who reply in advance and give opinions on the use of caustic soda and whether it worked for you or not. 

Thanks again.

 

[Strange]

6 minutes ago, yosafa said:

1. Will caustic soda actually do the job of unblocking the drains?

It should do. Basically it converts the fats into a water soluble form (soap) which should then wash away.

6 minutes ago, yosafa said:

3. Because the chemical gets hot when reaction with water, will this in turn damage the underground PVCu Drainage pipe or again will it just cool and wash away. I know the PVCu has high heat resistance though, does the chemical pass the PVCu heat threshold which may then cause damage. 

It is commonly used for this sort of thing. I guess the problem could be if you dump it in too quickly and there is a solid mass in the pipe that then gets hot. If you add it slowly so it dissolves (the heat should stir it naturally) it should be OK. If you buy a product intended for this purpose then it should have instructions on use. My hardware shop also sells concentrated acid (sulphuric, I think, or maybe hydrochloric) for clearing blocked drains. But I am always a bit worried about the effect on the cement, with that.

Make sure you wear gloves and eye protection in case of splashes.

[StringJunky]

5 minutes ago, Strange said:

It should do. Basically it converts the fats into a water soluble form (soap) which should then wash away.

It is commonly used for this sort of thing. I guess the problem could be if you dump it in too quickly and there is a solid mass in the pipe that then gets hot. If you add it slowly so it dissolves (the heat should stir it naturally) it should be OK. If you buy a product intended for this purpose then it should have instructions on use. My hardware shop also sells concentrated acid (sulphuric, I think, or maybe hydrochloric) for clearing blocked drains. But I am always a bit worried about the effect on the cement, with that.

Make sure you wear gloves and eye protection in case of splashes.

It'll be sulphuric acid. Hydrochloric acid is cement cleaner/mortar stain remover and the fumes of the concentrated stuff are very strong.

Edited December 6, 2017 by StringJunky

[Strange]

5 minutes ago, StringJunky said:

It'll be sulphuric acid.

I think you are right. Oddly, I don't think it says on the bottle (just lots of warnings about it being corrosive, etc.)

[DrP]

3 minutes ago, Strange said:

Make sure you wear gloves and eye protection in case of splashes.

I'd echo this. I am a chemist and would say that you are going the right way in treating it with respect.   I use it as a last resort to unblock drains.  Some people do suffer burns from the chemical when using it this way, but this can be avoided by treating it with respect - wear gloves (rubber) and eye protection.

I would also advise, if it doesn't unblock the drain, NOT to go back to pressure washers and things for some time afterwards...  you don't want to splash the solution back out of the pipe onto your self.   Regarding the heat generated during the dissolution of the NaOH I would say that this probably actually helps clear the blockage.

 

Last resort though...  I usually get good results from Mr Muscle's drainage un-blocker products and the 2 pack gels that react and gas to build pressure in the pipes to help unblock them.   NaOH has always worked as a last resort for me.

 

I have heard it said NEVER to put it down the toilet....  I have never had the need thankfully and probably would not just in case. I read somewhere once (years back) of a guy burning his, er, self with NaOH that he'd used in the loo to clear a blockage. The toilet water was still alkali some time after and splashes caused burns on his... er, body.

 

 

[studiot]

 

12 minutes ago, StringJunky said:

It'll be sulphuric acid. Hydrochloric acid is cement cleaner/mortar stain remover and the fumes of the concentrated stuff are very strong.

+1

Yes most likely sulphuric (car battery acid).

However hydrochloric is put into "limescale removers" for toilets, by bleach manufacturers.

It comes in black rather than blue bottles in the UK, but is easy to mistake.

 

The acid and tha alkali remove different componeents of a blockage.

As already described, caustic alkali (yes it is caustic so use rubber gloves) attacks the grease componenent which sticks things together.

But cellulose fibres in paper and cloth and other fibres such as hair and roots can be mechanically trapped in the drain.
That is where you should use the acid to dissolve them out, as the alkali will not touch that situation.

Always remove as much as possible mechanically first, since that will reduce the need for chemical action and is cheaper.

If you do use the acid, a bucket of washing soda (sodium carbonate) will flush it away safely afterwards.

The build up your referred to creates a highly nutrient soup for plants so they try to break into the drain with their roots.
This can be quite a nuisance with old drains.
 

Finally you should keep monitoring the situation and clearing before it gets to bad in future.

 

[Phi for All]

I was kind of hoping someone had a way to unblock a drain "just using logic". That would be awesome.

[studiot]

3 hours ago, Phi for All said:

I was kind of hoping someone had a way to unblock a drain "just using logic". That would be awesome.

Perhaps you should read Conway's new thread to find the answer to that particular question.

 

[John Cuthber]

If (as a home scientist)

6 hours ago, Phi for All said:

I was kind of hoping someone had a way to unblock a drain "just using logic". That would be awesome.

Did you hear about the constipated mathematician?

He worked it out with a pencil and paper.

 

If I want to buy sodium hydroxide or sulphuric acid over the counter, I buy them as drain cleaners.
Both chemicals are quite good at doing this. The instructions are written on the container. Follow them.

 

Don't mix the two materials.

 

Just in case you missed that

Really, don't mix them.