A pedestal sink has two parts: a basin bolted to the wall, and a pedestal that provides support while concealing the plumbing. Though more elegant-looking than your typical vanity cabinet, pedestal sinks have their downsides, one of the biggest being that it is rather difficult to get at the plumbing. When the sink gets plugged up and you need access to the trap to unclog it, you have to disassemble the sink. This is a job most handy homeowners can accomplish.
Dissemble Pedestal Sink
Determine whether the pedestal is bolted to the floor. Most pedestals are held in place simply with caulk and the weight of the basin resting on top, but some are bolted down. Reach behind the bottom of the pedestal and feel for bolts coming up through the bottom. If the bottom of the pedestal is closed up, or if you can't even get your hand back there to check, you can be confident there are no bolts.
Remove the bolts, if any, with a socket wrench.
Use a utility knife to cut through any caulk around the base of the pedestal and between the top of the pedestal and the bottom of the basin.
Slowly pull out the pedestal and move it aside. If the basin is especially large or heavy, it may want to pull away from the wall. If that appears to be happening, slide the pedestal back in place and follow the instructions in Section 2 for installing bracing.
Remove the U-shaped trap under the sink by unscrewing the collars on either end. With older plumbing, you may need a wrench or set of wide-mouth pliers to turn the collars. With newer plastic plumbing, you can turn the collars by hand.
Clean out the clog in the trap.
Replace the trap and tighten the collars.
Use a utility knife or razor blade to scrape away any caulk residue from the floor, the top of the pedestal and the bottom of the basin.
Slide the pedestal back in place under the basin.
If you installed 2x4 bracing, remove it now.
Apply new silicone sealant wherever you cut the caulk in Step 4.
Replace the bolts, if any.
Bracing for the Basin
Measure from the floor to the bottom of the basin. Cut two pieces of 2x4 lumber to that length.
Wedge the pieces of 2x4 lumber between the bottom of the basin and the floor on either side of the pedestal.
Pull out the pedestal and move it aside. The basin will rest on the lumber.