"Fredxx" wrote in message
...
On 31/01/2021 22:05, newshound wrote:
On 30/01/2021 16:15, Heaven wrote:
Hello all. Please can someone help. My brand new toilet somehow got
blocked. So, I poured a cap full of caustic soda down it and some
boiling water. Nothing happened. So I kept doing it, so much so that the
crystals have totally hardened and now, the hole has almost totally
blocked up and none of the waste is being flushed away. How can I
dissolve the totally rock hard caustic soda. Can I salvage my toilet??
Can it be cleared away. (Almost 10 days now). Thank you for your help.


If this is an accurate description, then be very very careful. Caustic
soda can "set" like this and be difficult to dissolve.

A fundamental problem is that if you have a blockage from more
"conventional" products beyond your new blockage, dissolving the caustic
soda still won't solve the problem (although if you can get caustic soda
solution through to them this may help).

Remember that caustic soda solution is *very* nasty if you get any in
your eyes or even on your skin. If you promote a rapid reaction with
boiling, etc, you can get spray.

Experienced chemists know how to dissolve granules in a small amount of
water by allowing it to get hot from the dissolution reaction but that
may be difficult in this geometry. There is also a risk of cracking the
porcelain from differential thermal expansion if some bits get much
hotter than others.

Someone else mentioned vinegar, this is a good and relatively safe way to
dissolve it, but assuming you have perhaps 500g of pure caustic soda
there then you may need 50 litres of vinegar. (ICBA to do the
calculation). What I think I might do is half-fill the pan with water,
then start dribbling in some brick acid, stirring it with a plastic or
wooden stick, and look for signs of a reaction. Pour in maybe a litre
stopping if there are signs that the reaction is speeding up. Leave it
overnight and try to establish by poking whether you have started to
clear it. If it is draining significantly, then repeat.

If not, the problem is unless you get some indicator paper (readily
available on eBay) you won't know whether the liquid in the bowl is
acidic or alkaline. If it is acidic, then it is not particularly
dangerous, but it means it is not reacting effectively. If it is
alkaline, then the approach is working but more acid is needed, and the
alkaline liquid needs to be handled with more care.

I'd know what to do at this stage. You'd need to find someone with good
A-level chemistry from 50 years ago, or a more recent chemistry graduate.
Or a fireman. Or perhaps an experienced old-school plumber, but do
explain to them how you got where you are.

I would have thought that given the caustic soda has already been added to
the pan, most of the exothermal reaction would have already passed.

You'd be wrong. The problem with caustic soda is that
it can get so hot that if melts and forms a very hard
crystalline form which doesnt dissolve readily anymore.

The logic thing to me is to add water, as you suggest slowly.

Trouble is that the very hard crystalline form
which doesnt dissolve readily anymore.

A pan full of water would dissolve the caustic soda.

Wrong, as always. If that was true, he wouldnt have a blockage.

And then hopefully diffuse its way to the blockage.

The hard crystalline form of caustic soda is the blockage.

However, most toilet blockages I have come across are down to foreign
materials and I suspect the OP's problem is no different.

You'd be wrong, as always.