Bloke at hardware store conned me into this s**te.
> Kitchen drain almost blocked - took out p-trap and it were
> clear, so fault is under the floor somewhere...
> The other drains in house flow freely.
> Before putting p-trap back, I poked about 3.5 metres
> flexible curtain wire down and it came out fairly clean,
> no streaks of grease.
> The bottle said use 250 ml, I did and waited 4 days.
> No better, so poured the other 750 ml in and waited 7 days
> without using the sink.
> And it is frickin worse now!
> (I always used caustic soda before - it worked)
If like us, your washing machine is plumbed into the same outflow pipe, you may find it is backed up from the washing machine end with a hard deposit of soap/scum/lime and fat, mixed together. If so, caustic soda could make it worse.
Luckily, in our case it is possible to push the garden hose (with spray end removed) up and down the outflow pipe from outside (hose is of the harder plastic type, and on full blast) until all the crap is broken up and flows out. Amazing how quickly this stuff builds up even if you don't have that many fry ups, and use liquid detergents!
Often, the first symptom you hear of this, is gurgling noises from one sink or basin when you empty another or the wm itself.
S