I recently redid my master bathroom. Since replacing the cultured marble countertop with sinks built in and new faucets the sinks drain slow. If I turn water off and let the water drain out when sink is almost empty there is a big air bubble that comes out of drain and then water drains OK until next use. I have lived in house since new and did not have this problem until I replaced sinks and faucets. Home is 19 years old,single floor Florida home with no basement. Plumbing is under the concrete slab. Drains have been cleaned and snaked. Thanks Karl

Does the new lavatory bowl have an overflow on it? Did you use an 1 1/2" trap or an 1 1/4" trap?

Yes the bowls have an overflow on them. I used 1 1/4" trap.

Have you used a plunger to clear the drain? You may have to switch to 1 1/2" trap

Yes I have used a plunger. Once the air bubble comes out they drain fine. But this happens evertime you go to use it.

Then it is either not vented correctly or you broke the hydrailic gradient