How much oil are you talking about?

And oil or grease (melted animal fat or other fats that are solid at room temperature)?

Do you have a garbage disposal?

COLD water and a GD should pulverize solid fats well enough to have them flush through.

Hot water and fats that can solidify on cooling are the problem.
They cool in the drain lines into a solid that can clog things.

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.

Hi brickeyee --I'm talking maybe about like 2-3lbs of fat every few years on the main sewer trap in the basement. It it white hard gunk when i pull it out. i live in a two family and most cooking is done on the second floor. First floor hardly cooks. We do not have a garbage disposer and we normally do not dump solids down and wipe our dishes with towels before washing them. The fat isn't clogging any of the kitchen traps but just the main after a few years.

lazypup -- yeah, i try not to use draino and just use my hands and gloves to grab the grease out and then clear it with a closet auger. I have 4.5 bathrooms in the house and I think it is 4 in PVCs last time I changed out the toilet. In the basement to the city sewer it is cast iron. I guess I'll just make it a yearly maintenance item to clean it.

Another question I have it about root growth I meantioned in the first post? Should I be concerned about it on cast iron piping to the city sewer?

Thank you both for your inputs.

Can your grease ...freeze it, then throw it out.

You would be wise to get someone to camera and jet the line so you can start over.

House traps and the use of fixture traps would almost be condsidered "double trapping" in any Plumbing code.

I personally love having house traps, cause it's easier for the Plumber/ drain cleaner to do what he has to do.

My father's house is 35 years old now, with a building trap, and we have not had 1 sewer back up ever. Matter of fact, when we built an addition onto the house 10 years ago, I had to cut into the main sewer line and guess what? It looked brand spanking new (ABS) all because we run water, and don't flush things down the drain that are not supposed to be flushed.

The other problem that wasn't mention was the 1.6 gallon toilets. Since 1996 when the government forced us to go to the 1.6 gallon toilet because we are trying to save the planet (sigh), it also created another problem that homeowners have no clue about. Not enough water is being flushed to "wash" the walls of the pipe down, so hence the build up in sewer lines.

Bottom line is...don't throw grease down the drain.

Hi Ozone89,

Thanks for your input. I'll get it cleaned yearly going forward.

What is your opinion on root growth I mentioned in the first post? Should I be concerned about it on new cast iron (XHCI) piping to the city sewer?

IMO, if this sewer line is new, it's going to be awhile before you start to have any major root problems.

Are there trees around this sewer line?

There are products out there to combat roots, but I don't think you will be able to purchase them yourself...trade only I think.

If you're that concerned with your sewer line, have someone send a camera down to take the guess work out of it, and make sure you get a copy for yourself. Stay away from the big drain cleaning companies and get a small company to come out and do this for you...you will save.

Also ask the opinion of that drain company with coming out once every so many years to jet the line for you to keep it clean and open.

But like I said, I would get a video first so you can see what you're dealing with, and that way nobody can lie to you.

You definitely don't want to start having grease build up in the line...you will be sorry.

Hi Ozone89 -- there is a big birch tree which seems to be 2 feet away from where the sewer line right before it connects to the city sewer system. So i guess you answered my question. Even new cast iron piping can get roots in them in the long term. I'll get a video and try to have it clean it yearly. Thanks!