Slow draining sink

[GeorgeE]

The fourth floor flat we recently moved into has a very slow draining sink. The sink trap and the initial plastic pipe is clear. A plumber we had doing another job pumped some air into the pipe with minimal effect he said that a blockage/gunge must be building up where the plastic pipe joins to a metal pipe that joins the communal down pipe in the pantry. To get to where the pipes connect he would have to take out the unit next to the sink and I want to avoid that. Is there anything safe to pour down the sink that will reach that part to clear it? George.

[Brianb]

There are various drain cleaners out there but I find caustic soda very effective, so long as there's no aluminium in the plumbing (there shouldn't be). Generally this stuff eats through most things.

[GeorgeE]

My concern is that it will settle in the sink trap that isn't blocked and any extra will just go straight down the drain. George.

[DIY]

The extra caustic soda that goes down the drain will hopefully dissolve some or all of the gunge in the process. The caustic soda that stays in the trap will flush away when you next turn a tap on. It can produce fumes so just put the plug in while you are waiting for the caustic soda solution to work.

[Tamale-Loco]

this stuff

Can you use caustic soda on plastic piping? I was told it would damage it if you did

T-L

[DIY]

Yes.

That was a false statement.

[Barb]

.A plumber we had doing

Did he use a Power Plumber aerosol thingy? I bought one of these from B&Q a couple of years ago for just the same problem - gunge out of reach. It's quite intense and spectacular, and I've never had the problem again.

Barb

[GeorgeE]

No he used a hand pump... like a big cycle pump. I did notice them later in a 'gadget shop. I'll have a look in B&Q for the aerosol. George