Hey all, just filled a tub in the back yard with a caustic soda mix to
clean up an old 2 stroke exhaust but it's just occurred to me that
there will be approximately 3 or 4 gallons of caustic soda / rust mix
to dispose of.
I am assuming I can dump it down the outside drain as caustic soda can
actually be used to clean drains?
Is the outside drain connected to a surface water sewer that goes to a local
stream? The aquatic wildlife might not like that! If it connects to a foul
sewer - OK.
Are you connected to a local foul sewer that goes to a sewage works? If so,
then down the kitchen sink or a bog would be the best bet.
Yep, sure can - be aware that any fat in the drain will turn to soap though,
and swells about 50% in the process, so running some *hot* water through
before and after could be a good idea if your drain's already a bit clogged?
On the subject of soda and cleaning steel, have you heard of the Bubbling
Electric Gunge Tank method for removing rust? Big plastic tub, battery
charger, half a cup of *washing* soda to each bucket of water, then connect
the +ve from the charger to a piece of scrap iron, -ve to the piece to
clean, leave for a few days - saves all that tiresome messing about with
wire brushes, strong acids etc., and often does a good job of stripping
paint too! (Google "electrolytic rust removal" for more details) The
leftover liquid's drain-safe as long as you don't use stainless for the +ve
electrode (which will eventually dissolve into the solution), stainless will
make lots of hexavalent chromium in the solution, which is Very Bad Stuff.
(The engineer formerly known as Homeless)
"Rules are for the obedience of fools, and the guidance of wise men" -
Depends what you mean by the outside drain. The ones in the street usually
go straight into a watercourse, though some on busy roads go into big soak
always to clean up the water a bit first. Car cleaning in the street can be
bad news for local river life, and garages with car washes, were, on a
survey I once did, the most common source of local river pollution - the
next being people plumbing in foul waste to the surface water pipes by
So best to check first and see where the waste goes when you flush the loo -
or pour a bucket at a time down the loo.
The solution in your tub will gradually turn to sodium carbonate solution
from contact with the air's CO2: this is 'washing soda', so what you would
be doing by pouring it down the foul sewer would not be greatly different to
doing a lot of washing. For other chemicals - like the chromium salts
mentioned in another reply - pouring down *any* drain is generally a no no.
If it is an older house (pre ww2? it probably depends a lot, but it
applied to our 1930's semi in Leeds) then you may well fin the foul
water sewer and the rain water drain combined.
It's easy enough to check - open a manhole and watch to see if both
foul water and rain water go down the same drain.
You actually have to boil vegetable oil or animal fats with caustic for some
time for specification. and it is not possible for mineral oils or paraffin
In testing oils, one key test of purity is its 'sap value'.
When oils are emulsified they are actually more polluting than when they are
separated out from the water environment: the difference would be like you
walking through a puddle of oil as opposed to having it sprayed at you in a
mist that you could not avoid breathing in.
Vegetable oils can be saponified (or personified, magnified, stratified,
if your spell checker prefers :-)) at room temperature. Solids, such as
wax, need to be heated, but only to their melting point.
Beeswax e.g. can be emulsified (i.e. made virtually soluble in water) at
70 degsC with the mere hint of alkali, or completely saponified (and
turned back into a solid) by adding more. Somewhere in between should be
a water based wax polish.
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