We have a small debate in my house. I don't like anyone pouring hot liquids down the drain ( coffee, straining pasta etc.) without at least running cold water from the tap. Ideally we should wait till liquids cool but I know that's not always possible. Can hot liquids harm the pvc drain pipes?

Nothing you are able to heat up will affect the PVC unless you are dumping hot turpentine or glue down there. Boiling water is only 212 degrees... not really that hot. Coffee is much less hot.

Edited to add: PVC has a melting point of 387 deg... nothing you can boil will come close to that.

Furthermore, drains flush quickly, so it would be the functional equivalent of passing your hand quickly through a candle flame.

Or in other words... dump water... its fine.

PVC is not recommended for any constant feed hot water (input lines) but the drains do not store hot water under pressure so there is no fear of heat related rupture.

Although Steve doesn't claim to be a plumber he sure sounds like one.
He's bang on with his response. Your fears about pouring hot liquids down the kitchen sink are groundless. He explained it much better then I could.
Nice catch Steve! Tom

Excuse my novice-ness, but aren't most drains ABS plastic? Or is ABS a type of PVC?

Excuse my novice-ness, but aren't most drains ABS plastic? Or is ABS a type of PVC?

Depends on where you live and when your home was built. The answer remains the same though... passing your hand through a candle flame...

Excuse my novice-ness, but aren't most drains ABS plastic? Or is ABS a type of PVC?

PVC and ABS are both plastic. They both will accept hot liquids.
There are four types of plastic in general use. Black plastic, which is ABS,(Acylonitrile Butadine Styrene) and white plastic which is PVC and CPVC,(Polyvinyl Chloride and Chlornated Polyvinyl Chloride) ABS is used for drainage. PVC is used outside the house for cold water feed from the pump or the meter Also drainage both inside and outside the house. CPVC is rated for both hot and cold lines and can be used to plumb a house on the inside and then we have Polybutylene pipe,(PB or Polly Pipe) which is flexible tubing on water piping.
And now you know more then you ever wanted to! Cheers, Tom