terra cotta sewer pipes as ollas?

I was reading up on ollas (unglazed terra cotta pots buried in the ground for watering plants by osmosis), and I suddenly remembered that the old sewer pipe leading from my house to the main used to be terra cotta. Does that mean that the sewer pipe leached water into the soil? Did it leach other stuff, or just water? If just water, could greywater be put directly into ollas to clean the water? Or would the scum build up on the inside of the pot and prevent further diffusion?

I expect terra cotta sewer pipes are probably glazed to prevent water (etc.) from leaching out. If you could find unglazed terra cotta pipe it'd certainly work as an olla. I'd think that greywater would plug the pores of the clay, and you'd end up with some nasty small cesspools.