In this instance you are confronted with a couple problems that most homeowners would never see. In the mid 80's the national model plumbing codes were amended to prohibit the installation of a "House Trap" at the junction of the building "Main Drain & house sewer" but I know for certain that NYC, Albany, Rochester, Buffalo and many other older cities in NY have ammended their local codes and still require the "house trap." There is a long list of reasons why the house traps were outlawed, but we will just examine the one that is giving you the most problems. As is common to all traps, the house trap has a water seal but the problem is, fats and cooking oils will float on top of the water seal and in a short time they form a cake over the top as if the water was iced over, and that cake of cooking oils and facts is what you are digging out of the trap. Short of snaking the drain there really is no good method of preventing that buildup. In fact, if you were to use the typical chemical drain openers such as Draino it can make the problem worse. Most over the counter drain opening chemicals are lye based and if Lye combines with animal fats it will actually produce a hard yellow lye soap just like our for Fathers did back in colonial times. Once that soap forms it is very difficult to clean out. I don't know how many bathrooms or plumbing fixtures you have in your house so it is difficult to be certain about your main drain & sewer line size, but suffice it to say that normally if you have a basic kitchen, laundry and not more than 2 bathrooms the proper size of the line would be 3", but here again, N.Y. is still holding firm to the 4" line. It may sound odd, but in reality an oversized line will clog much faster than an undersized line. When a line is properly sized at full load the horizontal pipe should be 1/2 full. This allows a good depth of water to carry any solids that are present in the waste, while still leaving the upper half of the pipe open for the transfer of vent air. If a line is oversized, the depth of flow is dramatically reduced, often enough that as the waste is flowing the solids, such as fecal matter are not fully suspended, but rather they drag and bump along on the bottom of the pipe. As this happens the liquids will flow around them and leave the solids laying in the pipe where they dry into a hard lump once the liquid has passed, and as you might imagine, the next time a solid hits that lump, it will stop and become another part of the lump until you are finally dealing with a clogged line.

Probably a combo of hair and goop in the drain. Get underneath and remove the P-trap - you'll likely find the stuff away. BTW, you might first try feeding a "zip-it" hair catcher directly down the drain (to snag and remove the stuff). Cost a couple bucks at the hardware store.

Okay, I've been reading up on this, and want to know if I understand it enough to do it myself. First of all, this is in a condo. There is no floor drain in the room, however there is a big pvc pipe that the overflow pipe from the waterheater goes into. If the hose fits into that, can I use that to drain it? If it doesn't fit........can I just put the other end of the hose in a big bucket, or into a nearby toilet?? I didn't know if the hose had to be lower than the water heater. I've read that I should: turn off power, shut cold water inlet, attach hose, open a hot water faucet, and let it rip. But....nothing comes out, so I'm assuming its hard chunks of stuff in there. I've been reading that I can take a screwdriver (or maybe a small dowel rod), and break the stuff up through the the heater's drain. Then, I'm supposed to turn on the cold water and let that flush it out. Do I need to close the outlet? Have I got it right so far? One article says to keep the pressure relief valve open during this time. Is that right? Is this something I should be letting a plummer do, or is it something I could manage myself? I just don't want a million gallons of black water all through the condo! I know I should probably run a hose all the way outside, but I worry about it somehow leaking all over the carpet, so I was trying to deal with it all very closely to the utility closet. P.S. For the water heater drain, it doesn't have a faucet....but rather a place to screw on a hose, with a little plastic lever you pull up to open it. It was VERY hard to move this lever. I hope I don't break it off. I put dish soap around it, hoping that would lubricate it, but it didn't help much. Thanks for your help.

"Shame on you, kitchensusie." Take it easy, she wasn't completely wrong, Liquid Plumbr contains both chemicals. The thing is that both are pretty harsh. Just because we are used to using bleach, doesn't mean that it isn't going to cause problems with the finish on the fixtures and such. Chlorine is a strong oxidizer and will cause metal to rust and discolor other finishes. Just a couple of other things I can think of, besides the plunger: 1. Try changing brands of shaving cream. Really, I think a big part of the problem is the formulation of this stuff. It's not really soap at all. 2. Mix a bucket of very hot water and dish soap (Dawn or Palmolive)and dump it down the drain about once a week. See if that doesn't help to remove the gunk. I would have recommended powdered Automatic Dishwasher detergent but it may discolor the marble.